THE ANATOMY OF TH-E BLOOD VASCULAR SYSTEM OF THE FOX ,SQUIRREL. §CIURUS NlGER. .RUFIVENTEB (OEOEEROY)

Thai: for the 009m of M. S. MICHIGAN STATE COLLEGE Thomas William Jenkins 1950

THulS' ifliillifllfllilllljllljIi\Ill\ljilllHliLlilHlLHl

This is to certifg that the

thesis entitled

The Anatomy of the Blood Vascular System of the Fox Squirrel. Sciurus niger rufiventer (Geoffroy)

presented by

Thomas William Jenkins

has been accepted towards fulfillment of the requirements for

A degree in MEL

Major professor

Date May 23’ 19500

0-169

q/m

Np”

THE ANATOMY OF THE BLOOD VASCULAR SYSTEM OF THE FOX SQUIRREL,

SCIURUS NIGER RUFIVENTER (GEOFFROY)

By

THOMAS WILLIAM JENKINS w L-Ooffi

A THESIS

Submitted to the School of Graduate Studies of Michigan

State College of Agriculture and Applied Science in partial fulfillment of the requirements

for the degree of

MASTER OF SCIENCE

Department of Zoology

1950 \ THESlSfi ACKNOWLEDGMENTS

Grateful acknowledgment is made to the following persons of the Zoology Department: Dr. R. A. Fennell, under whose guidence this study was completed; Mr. P. A. Caraway, for his invaluable assistance in photography; Dr. D. W. Hayne and

Mr. Poff, for their assistance in trapping; Dr. K. A. Stiles and Dr. R. H. Manville, for their helpful suggestions on various occasions; Mrs. Bernadette Henderson (Miss Mac), for her pleasant words of encouragement and advice; Dr. H. R. Hunt, head of the Zoology Department, for approval of the research problem; and Mr. N. J. Mizeres, for critically reading the manuscript.

Special thanks is given to my wife for her assistance with the drawings and constant encouragement throughout the many months of work.

sprr,i fij(?{) g.-.- -- . 1:: ,1. 51. CONTENTS

Page

Introduction...... l4

II. Materials and Methods...... h)

III. The Heart...... ,...... l»

IV. The Arterial System...... CD

A. The Thorax...... 0)

B. The Upper Extremity...... 12

C. The Head and Neck...... 29 D. The Abdomen and Pelvis ...... 43

E. The Lower Extremity...... 73

The Venous System...... 81

A. The Thorax...... 82

B. The Upper Extremity...... 85

C. The Head and Neck...... 86

a. The Superficial Veins of the Face 86 and HeadOOOOOO.0.0.00.0.OOOOOOOOOOOOOOOOO

b. Veins of the Neck...... 88

c. Superficial Veins of the Brain...... 89 d. Sinuses of the Dura Mater......

D. The Hepatic Portal System...... 96

E. The Abdomen...... 100

F. The Pelvis...... 102

G. The Lower Extremity...... 105

VI. List of References...... 107

VII. curriculum VitanO0.0000000000000000000000000.... 108 LIST OF ILLUSTRATIONS

Page

Fig. The heart, vessels of the thorax, and branches of the subclavian artery, ventral aspect...... 7

The left axillary artery and its branches... l9

Vessels of the upper extremity...... 23

Arteries of the head and neck, ventral

aspeCtOOOOOCOOO0.0.0.0.000...0..00...... O... 28

Vessels of the head and neck, lateral

aspeCtOOOOOOOOOOOOOOCOOOOOOOOOOOOOOOOOOOOOOO 33

Vessels of the brain, basal aspect...... 39

Vessels of the abdomen...... 42

Right external iliac and femoral arteries, showing branches of the pudic epigastric

trunkoo00000000...ooooooooooooooo00000000000 47

Blood supply of the male genitalia...... 51

10. Blood supply Of the testis and epididymis... 54

ll. The iliac vessels...... 59

12. Branches of the coeliac axis...... 62

13. Branches of the superior (anterior) 66 mesenteric.’.C...’...... OOCCOOOOO

14. Vessels of the lower extremity, medial

aspeCtOO00...... OOOOOOOOOOOOOOOOOOOOOOOOO... 72

Fig. 15, Vessels Of the popliteal fossa, medial

aspect....IOCOOCOCOOOOOOOOOOOOOOO0.0.0.0.... 77

Fig. 16. Vessels Of the brain, dorsal aspect...

Fig. 17. The hepatic-portal system...... 95 I. INTRODUCTION

In recent years there has been an increase in the in- terest in conservation studies. In contrast to the large number of projects dealing with game management and game utilization, there has been no carefully planned program for studies dealing with anatomical systems in rodents and other game animals. Hunt (1924) and Greene (1935) have described the anatomy of the rat, and Orwoll (l9AO) has described the osteology and myology of the fox squirrel.

It is the Object of this study to present a complete description of the anatomy of the blood vascular system of the fox squirrel, Sciurus niger rufiventer (Geoffroy),

Michigan's largest tree squirrel (Burt, 19A6, p. 192).

There has been no special attempt to completely compare the anatomy of the blood vascular system of the fox squirrel with other mammals, but there are described many differences in the circulatory systems of various mammalian species. II. MATERIALS AND METHODS

The seven fox squirrels used in this study were live— trapped in Baker woodlot, East Lansing, Michigan. The animals were embalmed and their circulatory system triply

injected with colored latex at the General Biological Supply

House in Chicago. The arterial system was injected with red latex, the venous system with blue, and the hepatic- portal system with yellow.

Seventeen figures are presented in addition to the descriptions given in the text. The figures are photographs of pen and ink plates which were traced from original drawings made at the time of dissection. A scale of 1 cm. appears in each figure. The veins are represented in the figures as darker vessels, and the arteries as lighter ones. In each figure the blood vessels are lettered and the related anatomical structures, such as muscles, are numbered. In the text, each vessel has after its name a

letter and a number of the figure to aid the reader in addition to the written description.

A speed graphic camera was used for all photography.

The photographs were taken with contrast process film, developed in contrast developer, and printed on Kodabromide

F-4 paper. III. THE HEART

The heart of the Sciurus niger (fig. 1) is a pear shaped

organ about 35 mm. in length. It lies in the middle mediasti— num and extends from the level Of rib three to rib six. It is enclosed within a sac which is known as the pericardium.

The wall Of the pericardium is composed of two layers: a) an external strong fibrous layer; and b) an internal serous ' layer. The fibrous layer extends a short distance along the great arteries and veins to fuse with the advential layer of these vessels. The internal serous layer consists of two portions: a) the parietal layer, which lines the

sac, and b) the visceral layer or epicardium (Maximow and

Bloom, 1947, p. 256), which covers the outer surface of the heart to give it a glistening appearance.

The apex of the heart lies free near the common tendon of the diaphragm, but the base is anchored in the mediastinum by the great vessels. The dorsal and lateral surfaces Of the pericardium are in contact with the paired pleural sacs, but

the ventral surface of the pericardium is mostly naked.

Fusion of the two parietal layers of the pleural sacs forms a partition, the mediastinal septum, which is demonstrable

as a thin membrane which extends from the ventral surface

of the pericardium to the ventral body wall.

The heart of this rodent is a typical four chambered mammalian heart. Its chambers are formed by a longitudinal and a lateral transverse (auriculoventricular) septum. The

anterior chambers, i.e. cephalad to the auriculoventricular septum, are called atria, and the inferior chambers are known as the ventricles. A rather deep groove runs diagonally across

the exterior of the heart to mark the separation of the auricles and ventricles. The sinus venosus is no longer visible as an entity, but has become incorporated into the wall of the right auricle. This may be correlated with the reason for the great systemic veins Opening directly into the right atrium. Embryologically, the conus arteriosus has split dichotomously into: a) the systemic aorta, which connects with the left ventricle; and b) the pulmonary trunk connecting with the right ventricle.

The course gf_the blood through the heart:

The course of the blood through the heart is essentially the same as it is in other mammals. The blood is returned to the right atrium of the heart from the body through the great systemic veins; the two superior venae cavae (precavae) (M,

and V, fig. 1) and the single inferior vena cava (post cava)

(X, fig. 1). From the right atrium the blood is passed through the tricuspid valve into the right ventricle. The latter pumps it through the pulmonary semilunar valve to the single pulmonary trunk. The trunk divides into the right and left pulmonary arteries which transport the blood to the hilus of the right and left lung respectively. Within the lung, the blood is chemically relieved of carbon dioxide and is oxygenated before returning to the left atrium of the heart by the numerous pulmonary veins. The blood of the left atrium passes through the mitral (bicuspid) valve to enter the left ventricle. The left ventricle, with its thick wall, pumps the oxygenated blood up through the aortic semilunar valves into the ascending aorta to be distributed throughout the body. FIGURE 1. The heart, vessels of the thorax, and branches of the subclavian artery, ventral aspect.

right common carotid superficial cervical transverse scapular transverse cervical acromiodeltoid cervical axis ascending cervical axillary vertebral mediastinal costocervical innominate right superior vena cava left internal mammary right internal mammary sternal ' ventral intercostals left common carotid left subclavian aortic arch pulmonary artery left superior vena cava coronary

xz

oesophagus first rib right auricle sternum trachea left auricle left ventricle

mflmmxwmw diaphragm

if“. I

2:23 II

. \

.

A‘ A

a

I.

59%

i

..

"V‘ ... .‘

cm. I

FIGURE 1 .

IV. THE ARTERIAL SYSTEM

A. The Thorax

The Ascending Aorta lies within the pericardial sac as the first portion of the aorta. It arises from the left ventricle to pass craniodextrad to leave the base of the heart between the two atria. The coronary arteries (W, fig.

l) arise from the aorta undercover of the auricles to dis- tribute branches over the heart wall. The Aortic Arch (T, fig. 1) is the continuation of the

aorta which curves dorsosinistrad.

Branches of the aortic arch:

a) Innominate b), Left Subclavian

a) The Innominate (Brachiocephalic) Artery (L, fig. 1)

is a unilateral vessel arising from the arch Of the aorta.

It lies ventrad and slightly towards the right side of the trachea as it traverses anteriorly one-half the distance to the first rib, where it gives rise to the left common carotid artery (R, fig. 1). The innominate then proceeds in a cephalodextrad course to the level of the first rib, where it gives rise to the right common carotid artery (A, fig. 1).

Distad to the origin of the right common carotid, the innom- inate is continued towards the axilla as the subclavian artery.

Greene (1935, p. 178) finds that therat is similar to man (Gray, 1936, p. 548) and to the rabbit (Hyman, 1947, p. 370) in that the innominate divides into the right subclavian \O and the right common carotid; in which cases the left common carotid arises directly from the aortic arch. The cat

(Reighard and Jennings, 1940, p. 282) and the squirrel have the left common carotid arising from the innominate as shown in figure 1. According to Crabb (1946, p. 62), in the rabbit the origin Of the left common carotid is incon— sistent and may arise from either the innominate or directly from the aortic arch. b) The Left Subclavian Artery (3, fig. 1) arises directly

from the aortic arch to course cephalolaterad to the level of the first rib where it turns towards the left axilla. The branches of the left subclavian are the same as those described for the right subclavian under the arteries of the upper extremity. The Pulmonary Artery (U, fig. 1) passes from the base

of the heart as a common trunk in a craniosinistrad direc- tion close to the aorta as shown in figure 1. Beneath the aortic arch the trunk divides dichotomously into a right and left pulmonary artery. The left pulmonary passes ventral to the bronchus and aorta, but dorsal to the left superior vena cava before reaching the hilus of the left lung. The right pulmonary passes dorsad to the aorta and right superior vena cava to reach the right lung. Just before the division of the pulmonary trunk, there is a short ligamentum arteriosum

(ligamentum Botallo) which connects the pulmonary with the

ventral surface of the aortic arch. This is a remnant Of the ductus arteriosus of Botallo which in foetal life connects the

pulmonary artery with the aorta. (Arey, 1947, p. 338). 10.

The Dorsal Aorta (Descendinngrta) is a posterior con-

tinuation of the aortic arch which passes through the trunk region where it is arbitrarily divided into the thoracic and the abdominal portions.

The Thoracic Aorta extends from the arch of the aorta

caudad to the diaphragm. Distad to the origin of the left subclavian artery, the thoracic aorta descends a little to the left of the midline during the first part Of its course; but as it approaches the diaphragm, it bears towards the right of the median line to continue caudad along the dorsal body wall at the left of the inferior vena cava and to the right dorsal side of the oesophagus.

Parietal Branches:

a) Intercostals b) Superior phrenic

a) The Intercostal Arteries appear as paired arteries

arising directly from the thoracic aorta. They are distrib- uted to the left intercostal spaces three to twelve inclusive, and on the right side from four or five to twelve inclusive.

The last two intercostals are covered ventrally near their origin by the quadratus lumborum and psoas muscles. Each artery divides into an anterior and a posterior ramus.

1) The anterior ramus lies between the internal and

external intercostal muscles. It runs slightly cephalolaterad to meet the nearest rib on its posterior side near its angle; where it accompanies the intercostal vein and nerve to con- tinue along the posterior surface of the rib. It follows the rib in this position and ultimately anastomosis with the ll. intercostal branch of the internal mammary (anterior inter-

costal) near the costal cartilage. The intercostal branch of the internal mammary artery is given off on the superior side of the rib by a common stem which bifurcates a short distance from its origin to send small branches which follow the anterior and posterior borders Of the ribs. Caudad of the eighth rib, the anterior rami extend laterad to supply the diaphragm. 2) The posterior ramus branches from the posterior

surface of the anterior ramus approximately 7 mm. from the aorta to course dorsad very close to the vertebral column where it sends a spinal branch through the intervertebral foramen to the spinal cord. It then continues dorsad to give off numerous branches to the muscles of the back.

The Superior Phrenic Arteries arise from the extreme

posterior portion of the thoracic aorta to extend laterad

\ upon the surface of the diaphragm. 12.

B. The Upper Extremity

The main arterial stem which supplies the upper extrem— ity is composed of four continuous portions from proximal to distal as follows: the innominate, the subclavian, the axillary, and the brachial. The last named artery divides distally into the ulnar and the radial arteries. The arterial blood supply will be considered in the above order. The Innominate (Brachiocephalic) Artery (L, fig. 1) has

been described in the previous section as an artery of the thorax. The Subclavian Artery (5, fig. 1; A, fig. 2) has a

different origin on each side of the body. The right sub- vlavian artery is very short, arising as the lateral branch of the bifurcating innominate and traveling only to the border of the first rib; the left subclavian artery is longer.'

It arises directly from the aortic arch as shown in fig. 1.

Upon reaching the first rib, both the right and the left sub- clavian arteries are similar and have corresponding branches as follows:

a) Internal mammary b) Costocervical

c) Vertebral d) Cervical a) The Right Internal Mammagy (0, fig. 1) arises from

the posterior surface of the subclavian artery immediately after the latter leaves the right common carotid artery.

The Internal Mammary passes dorsad to the right superior l3. vena cava in a caudoventral direction to reach the ventral wall Of the thorax at the level Of the second rib, approx— imately 2 mm. laterad to the sternal border. From here it passes caudad in a course parallel to the sternum between the muscles transversus thoracica and internal costalis.

Branches: l) ventral intercostals 2) mediastinal

3) perforating 4) sternal

5) superior epigastric

l) The ventral intercostal arteries (Q, fig. 1) arise

from the lateral side of the internal mammary at the level of each true rib. They are small branches to the rib for a short distance before bifurcating to have the ventral branch anastomose with the intercostal arteries Of the dorsal aorta. The ventral intercostal veins accompany the arteries and lie between the rib and the artery in each case. These vessels supply the intercostal muscles and send small branches through to the pectoral muscles.

2) The mediastinal artery (J, fig. 1) arises from the internal mammary artery close to its origin. The right mediastinal artery half encircles ventrally the superior vena cava to course mediad distributing branches to the lymph glands in the region, connective tissue, and the eosophagus before the main stem follows the lateral surface of the trachea distad to the bronchus where it is known as the bronchiol

branch. l4.

3) The perforating branches arise along the internal mammary artery close to the origin Of the intercostals discussed above. The perforating branches are small vessels which pass ventrad to penetrate the intercostal and pectoral muscles and finally reach the ventral thoracic wall, at the level of each rib, approximately 10 mm. lateral to the linea alba. They lie immediately inferior to the pectoral muscles in the form Of a dichotomous branching of minute arteries; one branch tending laterad, the other ventrad to supply the pectoral and dermal muscles in addition to the integument. 4) The sternal branches (P, fig. 1) arise segmentally from the medial side of the internal mammary to pass mediad to the sternum, to enter the intersegmental portions of the sternum. Usually each sternal artery lies on the caudal side of the vein, whereas the ventral intercostal arteries lie on the cephalic side of the corresponding vein (cf. fig. 1).

5) The superior epigastric artery is the extension of the internal mammary. It pierces the diaphragm to send small branches to the rectus abdominus muscle and other muscles of the ventral abdominal wall, and finally anas- tomoses with the inferior epigastric, of the external iliac. b) The Costocervical Artery (K, fig. 1) arises from the

subclavian at the same level as the internal mammary. The costocervical artery passes posteriorly along the dorsal wall of the thorax to enter a groove on the dorsolateral border of the longus colli muscle. The artery is rather incon— sistent in its distribution. On the right side this artery usually gives off branches to the first three intercostal 15.

spaces; whereas on the left side the artery usually supplies

only the first two intercostal spaces. c) The Vertebral Artery (I, fig. 1; B, fig. 2) arises

from the cephalodorsal surface of the subclavian artery at

'approximately right angles to the costocervical artery. It

proceeds directly beneath the longus colli muscle to disap-

pear as it travels through the transverse foramina (vertebral arterial canals) of the first six cervical vertebrae to

enter the skull through the foramen magnum. The vertebral

artery of one side joins its mate to form the basilar artery

as an important contribution to the blood supply of the brain (of. fig. 6). d) The Cervical Axis (F, fig. 1) arises from the

anterior surface of the subclavian at the level of the

origins of the arteries described above. It runs deep and

almost parallel to the external jugular vein as it courses

cephalad through the shoulder and neck region.

Branches: l) ascending cervical

2) acromiodeltoid 3) transverse scapular

4) superficial cervical 5) transverse cervical l) The ascending cervical artery (G, fig. 1) arises

from the medial surface of the cervical trunk close to its

base. It immediately divides into two main branches. One

branch runs in a cephalomediad direction ventrad to the

brachial plexus to reach the prevertebral muscles and pass 16. anteriorly along the surface of these muscles to the level

Of the cricoid cartilage of the larynx. Numerous small branches are given Off along its course to the prevertebral muscles. The second branch or deep branch Of the ascending

cervical proceeds dorsally through the plexus to supply the deep muscles of the neck before reaching the deep muscles of the upper back. 2) The acromiodeltoid artery (E, fig. 1) arises from

the lateral surface of the cervical axis approximately 1 cm. beyond the origin of the ascending cervical artery. The artery remains deep during the first part of its course laterad, before appearing on the ventral surface just an- terior to the clavicle. It then continues laterad over the external jugular vein to distribute branches to the acro- miodeltoid and pectoral muscles before it comes to lie ad- jacent to the cephalic vein.

After the cervical axis gives rise to the acromiodeltoid artery, the axis turns mediad to form an obtuse angle with the acromiodeltoid. 3) The transverse scapular artery (C, fig. 1) arises

from the cephalodorsal surface of the axis approximately

5 mm. beyond the origin of the acromiodeltoid. The trans— verse scapular artery immediately passes dorsad towards the scapula where it runs mainly along the supraspinatus muscle.

Along its_course, it distributes branches to the clavicular and shoulder joint regions and also to the surrounding muscles. 4) The superficial cervical artery (B, fig. 1) takes

origin from the anterior surface Of the cervical axis a short 17. distance beyond the transverse scapular. Its general course is cephaloventrolaterad to work its way through the neck muscles to finally become superficially distributed to the lateral cervical region and parotid gland.

5) The transverse cervical artery (D, fig. 1) appears

as a continuation of the cervical axis as it proceeds beyond the origin Of the superficial cervical to bend dorsad. It becomes superficial on the dorsal side as it runs approximately 1.5 cm. anterior of the transverse scapular artery to distribute its branches primarily to the supraSpinatus and trapezius muscles. The Axillary Artery (E, fig. 2; H, fig. 1) is a con-

tinuation of the subclavian artery, bounded proximally by the lateral border of the first rib or the cervical trunk, and distally by the latissimus dorsi. Distad to this muscle, the artery becomes the Brachial artery.

Branches:

a) Anterior thoracic (thoraco-acromial) b) Lateral thoracic (long thoracic, external

mammary) c) Circumflexo-subscapular trunk

a) The Anterior Thoracic (Thoraco-acromial) Artery

(D, fig. 2) is the first branch of the axillary artery. It is a thin artery arising from the ventral side of the axil- lary to pass somewhat medio-ventrad to supply primarily the pectoral and the rectus abdominus muscles. b) The Lateral Thoracic (Long Thoracic, External

Mammary) Artery (L, fig. 2) is given off from the axillary at

FIGURE 2. The left axillary artery and its branches.

left subclavian vertebral cervical axis anterior thoracic axillary circumflexo-subscapular humerO-circumflex anterior humeral circumflex posterior humeral circumflex subscapular scapular circumflex lateral thoracic

thoracodorsal ZUNQHmQWL‘UUOmb l9.

FIGURE 2 . 20. approximately one—half centimeter laterad to the anterior thoracic, and runs caudad with its corresponding vein and the medial anterior thoracic nerve which lie deep to the latissimus dorsi and the cutaneous maximus. Its branches are rather numerous and widespread, supplying a portion of the rectus abdominus, the deep side of the pectoralis major, the pectoralis minor, axillary lymph nodes, cutaneous maximus, and the dermis of the region involved. c) The Circumflexo-subscapular trunk (F, fig. 2) is a

very short trunk which arises from the anterior surface of the axillary artery approximately 1 cm. beyond the lateral thoracic to traverse in an Opposed direction. The trunk immediately divides into two main stems as follows:

1) the humero-circumflex stem 2) the subscapular artery

1) The humerO-circumflex stem (G, fig. 2) traverses a

cephalolaterad course to pass beneath the proximal portion

Of the coracobrachialis muscle. Directly under cover Of the coraco brachialis muscle, the trunk gives off its first branch, the anterior humeral circumflex artegy (H, fig. 2),

which supplies the biceps near its origin as well as sending small branches to the head of the humerus.

The main stem Of the artery continues deeply as the posterior humeral circumflex artery (I, fig. 2), which passes

posterior to the humerus through a triangle formed by a) the scapular end of the long head of the triceps, b) the axillary border Of the scapula, and c) the latissimus dorsi muscle.

On the lateral side of the appendage, the course is distally 21. underneath the lateral and long heads of the brachii and the brachialis muscles. A prominent branch extends distad between the muscles brachialis and the supinator longus to cross into the superficial fascia of the anticubital fossa and extends distad as a small superficial artery in the fascia along the border Of the muscle supinator longus to finally join the portion Of the cephalic vein in the lower arm.

2) The Subscapular Artery (J, fig. 2) arises from the posterodorsal surface Of the circumflexo-subscapular trunk to divide almost immediately into two vessels; a) the scapular circumflex artery (K, fig. 2) which is a small artery passing parallel but deep to the humerO-circumflex system. The artery passes between the subscapularis and the teres major muscles to pass towards the axillary border of the scapular; and b) the thoracodorsal artery (M, fig. 2)

passes caudad dorsal to the axillary vessels to join the thoracO-dorsal nerve in the muscle latissimus dorsi.

The Brachial Artery (A, fig. 3) is a direct continuation of the axillary artery distad into the arm beyond the origin of the subscapular. The artery is accompanied by the basilic vein, the median and ulnar nerves but does not pass through

fine supracondyloid canal of the humerus as does the median nerve.

The upper portion Of the brachial artery lies deep to the median and ulnar nerves; but at approximately one-half its course, it passes around both nerves to cross over to reach the anti-cubital fossa. FIGURE 3. Vessels of the upper extremity.

brachial ulnar collateral

/ recurrent ulnar ulnar. interosseus radial rami musculares transverse cubital recurrent radial cephalic vein

CAHIEQ’IJEUUOUZ’P 23.

is

1 cm.

FIGURE 3. 24.

Branches: l) superior profunda (a. profunda brachii)

2) rami musculares

3) transverse Cubital

4) ulnar collateral (a. anastomotica magna)

5) radial

l) The superior profunda artery (a, profunda brachii)

arises from the first part of the brachial, to pass deep

towards the dorsal side of the appendage. It supplies the

triceps, epitrochlearis, and the latissimus dorsi muscles.

2) The rami musculares are branches given off from

the brachial artery along its course. Constant rami are

found near the supracondyloid foramen of the humerus leading

to the biceps, epitrochlearis, and brachialis muscles. 3) The transverse cubital artery (H, fig. 3) arises

from the medial surface of the brachial artery at the level

Of the olecranon to pass mediad beneath the tendon of the

biceps brachii and coracobrachialis. The artery distrib- utes branches on the radial side Of the upper forearm to

supply muscles in that region.

4) The ulnar collateral (a. anastomotica magna) artery

(B, fig. 3) is given Off from the brachial artery proximal

to the supracondyloid foramen to pass in a laterodistal

direction to supply the area about the olecranon.

5) The radial artery (F, fig. 3) is the direct con-

tinuation of the brachial artery beyond the convexity Of

the elbow. 25.

Branches: a) recurrent radial b) recurrent ulnar

c) interosseus

d) rami musculares

e) ulnar a) The Recurrent Radial Artery (I, fig. 3) appears as

a deep branch of the radial artery at the bend of the elbow just beyond the supracondyloid canal. The artery travels distad towards the radial side of forearm deep to the tendon of the muscle biceps to extend mainly along the extensor carpi radialis muscle. b) The Recurrent Ulnar Artery (C, fig. 3) arises at

the lateral border of the tendon of the biceps muscle to progress laterad towards the ulnar side supplying the muscles pronator teres, and the proximal portion Of the flexor profundus digitorum. I c) The Interosseus Artery (E, fig. 3) appears distad

of the biceps tendon as it passes deep towards the inter- osseous membrane, on which it follows distad supplying the flexor digitorum profundus and the pronator quadratus. A nutrient artery to the radius is given Off from the proximal portion Of this artery. d) The Rami Musculares (G, fig. 3) are muscular branches

given Off at random along the course of the radial artery. e) The Ulnar Artery (D, fig. 3) arises from the radial

artery as it crosses over the tendon Of the biceps muscle.

The ulnar artery passes deep towards the ulnar side of the :forearm to follow distad the inside border of the flexor carpi ulnaris muscle. This artery supplies the flexor profundus digitorum, palmaris longus, and the flexor carpi ulnaris muscles. It passes distad along the last named muscle to the wrist. Near this location it sends off a branch towards the volar surface which runs along the radial side of the pisiform bone to anastomose with the radial to form the palmar arch.

The Palmar Arch is formed as stated above by the ter-

mination of the radial artery anastomosing with the ulnar artery within the palm of the hand.

Branches of the palmar arch:

a) A. Princeps pollicis et indicis

b) Palmar interosseae

a) The A. Princeps Pollicis gt Indicis passes from

the palmar arch near the radial end of its loop to send a branch to the ulnar side of the thumb and one to the radial side of the index digit.

b) The Palmar Interosseae are three arteries which

leave the palmar arch to pass distad in the intervals between the four ulnar digits. The extreme radial one passes along the ulnar side of the first digit; the ulnar branch along the radial side of the fifth digit. FIGURE 4. Arteries of the head and neck, ventral aspect.

lateral nasal superior labial lacrimal palpebral orbital superficial temporal superficial temporal masseteric inferior labial internal maxillary external maxillary (facial) external carotid anterior auricular posterior auricular occipital internal carotid external carotid superior laryngeal superior thyroid left common carotid submental lingual

S4CHM$DWOZZE4WQHCEQWWUOW> glandular ductus parot:ideus external auditory canal dentary geniohyoid parotid gland sternohyoid sternomastoideus NOW-P'UJIDH 28.

‘ , r. .

f \ (I)

.3 5 \ en.“ \ . ’ \

U0

EIT moi-4mm

0220!:th

”'0

m

"3

FIGURE 1L .

29.

C. The Head and Neck

The Left Common Carotid Artery (T, fig. 4; R, fig. 1)

arises from the left side of the innominate to pass sinistro- laterad across the trachea to form the left arm of a ”Y” shaped formation, with the innominate forming the other arm and the base of the "Y" as shown in fig. 1. The courses of the two common carotids are similar in that they traverse cephalad to parallel the trachea on each side to the level of the thyroid cartilage of the larynx, where they divide dichotomously to form the external and internal carotid

arteries.

The Superior Thyroid Artery (S, fig. 4) is the only

branch of the common carotid. It arises from the medial surface of the common carotid at the level of the crico- thyroid ligament of the larynx. It passes mediad to send branches to the thyroid gland before turning caudad to follow the lateral border of the trachea. The superior laryngeal artery (R, fig. 4) leaves the superior thyroid

to pass mediocephalad across the thyroid cartilage to supply the laryngeal muscles. This origin of the superior thyroid artery in the squirrel is similar to that found in the cat (Reighard and Jennings, 1940). In the rat (Hunt,

1924, p. 57) and man (Gray, 1936, p. 552) the superior thy- roid arises from the external carotid artery. The External Carotid Artery (Q, fig. 4; B, fig. 5) arises

as one of the stems of the bifurcation of the common carotid at the level of the thyroid cartilage of the larynx beneath 30. the posterior belly of the muscle digastricus. It appears

as a main anterior continuation of the common carotid

artery for a short distance before giving off a conspicuous ventral branch, the external maxillary (facial artery)

(K, fig. 4). At this point the external carotid turns

sharply dorsad to follow the posterior border of the mas-

seter muscle. Anterior to the auditory bulla, the artery

divides into its two terminal branches, the superficial

temporal (F, fig. 4) and the internal maxillary (J, fig. 4).

Branches:

a) Occipital b) Lingual

c) External maxillary (facial)

d) Posterior auricular

e) Masseteric

f) Anterior auricular

g) Superficial temporal

h) Internal maxillary a) The Occipital Artery (0, fig. 4) arises from the external carotid close above the bifurcation of the common

carotid. It crosses the internal carotid artery ventrally

to run dorso-laterad posterior to the ear to extend unto

and supply the dorsal muscles of the neck.

b) The Lingual Artery (V, fig. 4) arises from the

external carotid at the level of the hyoid bone which

covers it along with the posterior belly of the digastricus

muscle. It courses craniad and deep, parallel, and mediad to

the external maxillary artery to finally reach the base of

the tongue. 31.

c) The External Maxillary (Facial) Artery (K, fig. 4;

G, fig. 5) leaves the external carotid at the point where the ramus of the mandible is reached near the posteroventral border of the masseter muscle. The external carotid turns at a sharp angle to course dorsad along the posterior border of the masseter muscle; while the external maxillary artery turns at an angle opposed to the carotid to run ventrad between the ventral border of the masseter and the anterior belly of the digastric muscles.

At the anteroventral border of the masseter muscle near the origin of the digastric muscle, the external maxillary artery crosses the mandible superficially to traverse rnterodorsad along the anterior border of the masseter muscle in the facial region. After passing the corner of the mouth and giving off the superior labial artery (I, fig. 5),

the external maxillary is known as the angular artery (K).

Branches:

l) glandular

2) submental

3) masseteric

4) inferior labial 5) superior labial 6) angular

l) The glandular branches (E, fig. 5) are usually two

vessels arising from the ventral side of the facial artery.

One is a large artery directed posteriorly to supply the submaxillary and sublingual glands. The second vessel is less consistent, and usually supplies the lymph glands in the neck region. FIGURE 5. Vessels of the head and neck, lateral aspect.

external Jugular external carotid posterior facial anterior facial glandular masseteric external maxillary inferior labial superior labial lateral nasal angular nasal transverse facial supraorbital lacrimal palpebral orbital superficial temporal internal maxillary anterior auricular posterior auricular vein from ptengoid plexus

trachea ductus parotideus masseter muscle

DUMP . m mmDmVHm

.mm 34.

2) The submental artery (U, fig. 4) arises from the

external maxillary near the middle and beneath the anterior

belly of the digastricus muscle. The artery is directed

mediad and craniad to be found in the gum at the base of

the lower incisors on the dentary border of the vestibule.

3) The masseteric arteries arise from the lateral

side of the facial artery to distribute themselves exten-

sively through the masseter muscle.

4) The inferior labial artery (I, fig. 4) arises from

the external maxillary immediately after the latter crosses

the dentary. The inferior labial artery passes craniad

and then divides to send a branch to the dentary through

the mental foramen, and also branches to the lining of the mouth and the lower lip.

5) The superior labial artery_(B, fig. 4) leaves the

external maxillary just above the angle of the mouth. After

giving off the lateral nasal artery(A, fig. 4), which is

directed towards the nose, the superior labial artery con—

tinues forward to supply the upper lip. 6) The angular artery (K, fig. 5) is the terminal

portion of the facial artery which continues dorsad after giving off the superior labial branch. The general course

of this artery is to arch dorsad and caudad to direct itself

towards the eye. d) The Posterior Auricular Artery (N, fig. 4) arises

from the external carotid in the space between the tympanic bulls and the dentary near the border of the sternomastoideus muscle. It courses posterolaterad to reach and supply the parotid gland and the muscles behind and above the ear.

e) The Masseteric Arteries (H, fig. 4) are given off

from the external carotid along its course which enter and supply the masseter muscle.

f) The Anterior Auricular Artery(M, fig. 4) arises

from the external carotid at the upper posterior corner of

the masseter muscle. It courses dorsad to reach and supply the anterior portion of the pinna.

g) The Superficial Temporal Artery (R, fig. 5) is one of the terminal branches of the external carotid. After giving off the anterior auricular artery, the external carotid bifurcates into the superficial temporal and the internal maxillary arteries. The internal maxillary takes a deep course, while the superficial temporal traverses over the lateral surface of the masseter muscle approxi— mately one centimeter above and parallel to Steno's duct

(ductus parotideus). The superficial temporal artery gives off the following branches:

1) masseteric

2) transverse facial 3) orbital

l) The masseteric branch passes from the superficial temporal artery to the masseter.

2) The transverse facial (M, fig. 5) courses craniad on the surface of the masseter muscle which it supplies in addition to the integument. 36.

3) The orbital (Q, fig. 5) divides into the palpebral

(P), which supplies the upper eye lid, and a lacrimal branch

(0) to the intraorbital lacrimal gland. h) The Internal Maxillary artery (S, fig. 5) is the

other terminal branch of the external carotid (of. super— ficial temporal above). It hrs two branches which are identified as the following: 1) The inferior alveolar

artery which runs medial to the dentary to enter the mandibular foramen; and 2) the pterygoid portion which

traverses lateral to the mandible to supply primarily the cheek muscles of mastication.

The Internal Carotid Artery (P, fig. 4; E, fig. 6)

arises from the posterolateral surface of the common carotid at the level of the thyroid cartilage by a dichoto- mous branching of the common carotid. The medial division of the common carotid is designated as the external carotid.

The internal carotid passes cephalad and dorsad to the occipital and external carotid arteries. Its course is almost parallel to the external carotid artery. Near the posteromedial border of the auditory bulla, the internal carotid gives rise to the pterygopalatine artery. This

vessel enters the bulla and continues through the anterior wall of the bulla to distribute its branches throughout the medial and forward portions of the head.

The internal carotid continues as a very small artery along the medial border of the bulla to enter the skull through the carotid canal. The internal carotid was not positively identified again until it joined the Circle of willis (fig. 6). 37.

Branches of the internal carotid artery in the cerebral region: a) The Posterior Communicating Artery (I, fig. 6)

arises from the internal carotid on the ventral surface of the brain lateral to the hypophyseal stalk (6, fig. 6). It passes posteriorly and medially to encircle the hypophysis, where it anastomoses with the basilar artery in the midline. l) The posterior cerebral artery (F, fig. 6) is the

lateral branch of the posterior communicating artery. It traverses laterad under cover of the cerebral hemisphere to ultimately reach the occipital lobe. b) The Anterior Cerebral Artery (D, fig. 6) is the

most anterior of the terminal branches of the internal carotid artery. Its course is directly opposed to the posterior communicating artery, i.e. it passes around the basal stalks of the optic chiasma (2, fig. 6) to reach the midline. A branch (A, fig. 6) leaves anteriorly to border the division between the right and left hemispheres in the anterior region on the ventral surface of the hemispheres.

l) The middle cerebral artery (C, fig. 6) is the

largest artery which extends laterad over the ventral sur— face of the hemisphere as shown in fig. 6; and it continues over the dorsal surface of the hemisphere as shown in fig.lfh

A review of the literature shows that the Circle of

Willis is interpreted in a number of ways. There is varia- tion among different species and among different specimens within the same species. The discussion here is in agree- ment with Greene (1936, p. 186) in her discussion of the

Circle of Willis of the rat. FIGURE 6. Vessels of the brain, basal aspect.

anterior cerebral branch

O superior cerebral

O middle cerebral

O anterior cerebral

O internal carotid

O posterior cerebral

O inferior cerebral

O basilar

O posterior communicating superior cerebellar

WQHCEQQWUOEUP vertebral

optic chiasma

O trigeminal nerve

O cerebellum

O olfactory tract

0 cerebral hemisphere ONU‘I-P'UJI'DH hypopyseal stalk (cut)

b

la! p / \

0‘

0-41.")

U

1 cm.

FIGURE 6 . 40.

The Circle gf_Willis is formed on the base of the brain primarily by the anterior cerebral and the posterior com-

iunicating arteries. Both of these arteries are branches

of the internal carotid artery. The anterior arc of the

”circle" is formed by the anterior cerebral passing around

the lateral side of the basal stalks of the optic chiasma

to meet its mate anterior to the chiasma. The posterior

arc is formed by the posterior communicating arteries passing posterior to the hypopyseal stalk on each side to arch mediad to meet its mate at a common point of fusion with the basilar artery as shown in fig. 6. FIGURE 7. Vessels of the abdomen.

right inferior phrenic left inferior phrenic superior suprarenal coeliac axis adrenolumbar inferior suprarenal (accessory) inferior suprarenal renal ureteric abdominal aorta left colic posterior (inferior) mesenteric superior haemorrhoidal anterior (superior) mesenteric posterior vena cava internal Spermatic (male); ovarian (female) iliolumbar common iliac middle caudal (sacral)

womOZZBWQHmeMUOw>b

colon diaphragm right kidney ureter

rwmw 42.

I

\ ‘ \ ,9, f 2 \ .‘ \ “. .l‘ ‘ / \ \~ 3 _ \‘ !.' ‘\\ ’ i. ., V. ‘7‘” Ti." . \ _ “ . ,1, . C.—7 J11 1" ' \ ’ \‘\ K / J ‘

{/

.J

0h

t H. . Q J___.,"

\

5’ 1 cm.

FIGURE 7 .

43.

D. The Abdomen and Pelvis

The Abdominal Aorta (I, fig. 7) is that portion of the

dorsal aorta which is a posterior continuation of the thoracic aorta extending from the diaphragm to the origin of the common iliac and caudal arteries. It lies slightly to the left of the mid—dorsal line to traverse retroperitoneally immediately to the left of the inferior vena cava.

I. PARIETAL BRANCHES

A) Inferior phrenic

B) Lumbar

C) Iliolumbar D) Middle caudal (sacral) E) Common iliac II. VISCERAL BRANCHES

A) Coeliac axis B) Anterior (Superior) mesenteric C) Posterior (Inferior) mesenteric

D) Superior suprarenal

E) Inferior suprarenal F) Internal spermatic (male) G) Ovarian (female)

I. PARIETRL BRANCHES:

A) The Inferior Phrenic Arteries are asymmetrically

arranged. The left inferior phrenic (A, fig. 7) arises directly from the aorta, to pass craniad and cross the superior suprarenal artery before piercing he posterior surface of the diaphragm near the mid—line. The right 44. inferior phrenic (A', fig. 7) is a branch of the right

renal artery. It ascends to give off branches to the right

adrenal gland before it reaches the diaphragm on its respec-

tive side of the mid—line as shown in fig. 7. B) The Lumbar Arteries are seven in number, which arise

from the dorsal surface of the aorta to take a deep dorsal

course, to pass between the psoas and quadratus lumborum muscles. The first two arteries (most cephalad) are cov—

ered by the crura of the diaphragm; the third arises oppo-

site the superior mesenteric artery; the fourth is slightly

posterior to the origin of the left renal artery; the fifth

is about midway between the left renal and the inferior

mesenteric arteries; the sixth arises immediately anterior

to the origin of the iliolumbar arteries; and the seventh branches from the middle caudal (sacral) artery. C) The paired Iliolumbar Arteries (P, fig. 7; M, fig. 8)

arise from the lateral surface of the abdominal aorta at

variable distances from the origins of the inferior mesen-

teric and internal spermatic arteries. The arrangement

shown in figures 7 and 9 was found to be the most common,

but the right iliolumbar may take origin at the same level

or cephalad to the left iliolumbar artery. The iliolumbar

arteries course laterad over the ventral surface of the

iliopsoas muscle to reach the body wall where they distribute

branches throughout that region. A consistent posterior

(iliac) branch pierces the abdominal wall close the inguinal

ligament to pass over the upper lateral surface of the sar-

torius muscle. 45.

D) The Middle Caudal (Sacral) Artery (R, fig. 7;

C, fig. 8) appears as a direct continuation of the abdominal aorta as it prsses caudad near the midline over the ventral surface of the sacral vertebrae into the tail. This artery gives rise to the last lumbar artery, and also the lateral caudal arteries which traverse along the lateral sides of

the tail. E) The Common Iliac Arteries (Q, fig. 7; C, fig. ll)

arise by the bifurcation of the abdominal aorta appr ximately five millimeters distad to the origin of the inferior mesenteric artery. They extend in a caudolaterad direction to approach the medial surface of the iliopsoas muscle, where each divides to form the external and internal (hypo—

gastric) arteries. The common iliacs are retroperitoneal

in position and each is crossed ventrally by the ureter near the posterior boundary of the peritoneal cavity. The left common iliac, unlike the right, is crossed ventrally by the superior rectal (haemorrhoidal) artery and the pelvic

mesocolon.

The External Iliac Artery (I, fig. 11; 0, fig. 9) ap-

pears as a direct continuation of the common iliac artery as it traverses in a caudolaterad direction towards the medial side of the thigh. Immediately anterior to the point where this vessel pierces the body wall, the pudic epigastric

trunk arises from its medial surface. After passing through the body wall, the external iliac continues to the medial side of the thigh, where it is known as the femoral artery.

FIGURE 8. Right external iliac and femoral arteries, showing branches of the pudic—epigastric trunk.

abdominal aorta common iliac middle caudal superior gluteal external spermatic deep external pudendal inferior epigastric superior external pudendal pubic branch branch to thigh (adductors) femoral inferior vena cava iliolumbar hypogastric (internal iliac) pudic-epigastric trunk deep circumflex iliac

"UOZZt‘WC-JHL‘EQ’TIJEUUOWP

|--' iliopsoas muscle 47.

o

[,1 if!!!” 1 H

l

, v 'IIQH‘ L WWII'H'I '1. 1 cm.

FIGURE 8 .

48.

Branches:

Pudic-epigastric trunk

Femoral Artery a) The Pudic-epigastric Trunk (0, fig. 8) arises from

the external iliac as stated above. Shortly after leaving the medial surface of the external iliac it forks to send branches to the body wall, genitalia, lateral ligament of the bladder, and the adductors of the thigh. In one speci- men studied there was no pudic-epigastric trunk present; in which case the main stems arose independently from the external iliac.

Branches of the Pudic-epigastric Trunk:

a) Deep circumflex iliac b) Inferior epigastric c) External Spermatic (male)

d) Superior (superficial) external pudendal

e) Inferior (deep) external pudendal a) The Deep Circumflex Iliac (P, fig. 8) arises near

the base of the pudic-epigastric. In some specimens it appears to be an independent branch of the external branch of the external iliac in very close apposition to the pudic- epigastric trunk. After leaving the trunk, it passes medially for a short distance and then it turns laterad and anteriorly to cross the external iliac. Its anterior course is continued between the muscles obliqus internas and transversus. b) The Inferior Epigastric Artery (G, fig. 8) is not

typically an independent branch of the external iliac as it 49. is in man (Gray, 1936, p. 619). In the squirrel this artery arises as one of the main stems of the pudic—epi- gastric trunk. It passes directly to the ventral surface of the rectus abdominus muscle, and continues craniad to supply that muscle, and adjacent muscles of the abdominal wall. Its anterior terminal branches anastomose with the terminal branches of the superior epigastric artery, a branch of the internal mammary artery. 0) The External Spermatic (Cremasteric) Artery (E,

fig. 8) is in close proximity to the inferior epigastric, and in most specimens it appears as a branch of that artery.

It follows the spermatic cord, to supply primarily the cremasteric muscle.

d) The Superior (Superficial) External Pudendal Artery

(H, fig. 8) arises close to the origin of the inferior epigastric, and in some specimens it appears to be a branch of the inferior epigastric. In the male the artery passes to the base of the penis where it supplies the surrounding tissues, and passes distally along the penis to supply the prepuce. In the female, the Superior (Superficial) External

Pudendal Artery is accompanied by its vein to supply the

mammary gland in the inguinal region and sends a branch caudad to the labial region. e) The Inferior (deep) external pudendal (F, fig. 8) is

quite variable in origin and distribution. It is directed along the lateral ligament of the bladder, where it gives off many branches to this membrane and to the tissues at the base of the penis. FIGURE 9. Blood supply of the male genitalia.

abdominal aorta

O inferior vena cava

O iliolumbar

O internal spermatic

O Inferior mesenteric

I common iliac

O superior gluteal O internal iliac (hypogastric)

O inferior vesicular

O femoral

O deferential

O pampiniform plexus testicular dorsal artery of penis external iliac superior vesicular

"UOZZWWMHEQWWUOWD

anal gland penis testis colon vas deferens

GUI-twmi-J urinary bladder 51.

‘/ 'I-

on:

F]

HmO’lJ

HM

t" '3': ..

FIGURE 9 . 52.

In the female, the Inferior (Deep) External Pudendal

Artery supplies the lateral ligament of the bladder and sends a small branch along the surface of the urethra to the wall of the vagina. The Hypogastric (Internal Iliac) Artery (H, fig. 11;

N, fig. 8) arises from the ventral side of the common iliac artery as a trunk near the level of the sacro-iliac joint.

The branches of this trunk are so variable that the dis- cussion of their courses is necessarily somewhat general

in nature.

Branches:

A. VISCERAL BRANCHES a) Superior vesicular b) Internal pudendal

B. PARIETAL BRANCHES a) Obturator

b) Lateral femoral circumflex

c) Superior gluteal

A. VISCERAL BRANCHES:

a) The Superior Vesicular artery(P, fig. 9) generally

arises from the medial surfaces of the common iliac in

such close proximity to the hypogastric trunk that it may appear in either of two relationships: a) as an independent branch of the common iliac, as it is shown in fig. 9; or b) as a branch of the hypogastric trunk. Due to the fact that

this artery represents the stem of the fetal hypogastric (umbilical artery) (Hamilton, 1948, p. 138), it is most

commonly considered, in its own right, under branches of the FIGURE 10. Blood supply of the testis and epididymis.

internal spermatic epididymal branch pampiniform plexus testicular branches to fat

deferential @WUOWP

caput epididymis testis vas deferens corpus epididymis

cauda epididymis U'I-P’UUNH 54.

..... A

_ .B

C

.\ 1 S‘% ‘\ v.\.;. ”I, gust?“ u J\~;/

lIll"! 3‘ " i

2

.L_Qm

FIGURE 10 .

55. hypogastric trunk. The Superior Vesicular artery runs distally, to give off the following branches:

1) inferior vesicular artery

2) deferential (male) 3) uterine (female) 1) The inferior vesicular artery (I, fig. 9) arises

from the superior vesicular artery at the level of the base of the bladder, to turn medially towards that organ which

it supplies.

2) The deferential artery (artery of the ductus deferens)

(K, fig. 9; F, fig. 10) appears as a direct continuation of the superior vesicular artery, to accompany the ductus deferens to the testis.

3) The uterine artery in the female leaves the superior

vesicular while in the lateral ligament of the bladder to cross the ureter ventrally and travel distad within the broad ligament of the uterus where it gives off many branches to that organ. Its terminal branches anastomose with the ovarian artery. b) The Internal Pudendal Artery (0, fig. 11) arises

from the dorsal surface of the hypogastric trunk as a terminal branch. It is somewhat variable in its origin and as a consequence it is difficult to decide whether to con-

sider it a terminal branch of the hypogastric trunk or a branch of the obturator artery. The internal pudendal runs parallel with the superior gluteal artery, being

separated from it by the hypogastric vein. These two arteries and the internal pudendal vein run dorsad in the 56. pelvic cavity to cross deep to the sciatic nerve and pass laterad to leave the pelvic cavity to appear on the dorsal side of the animal traversing close to the sciatic and adjacent nerves from the sacral plexus in a caudo-laterad direction deep to the gluteal muscles and close to the origin of the tail muscles. From a dorsal View the internal pudendal artery can be seen to run caudad in a medial posi— tion accompanied by the nerve of the same name. At the base of the tail, the artery cuts in a medio-ventral direc- tion to pass between the base of the tail and the anal gland through the ischio-rectal fossa where it is known as the artery 93 the penis in the male, and the artery of the

clitoris in the female.

The Artery of the Penis passes just lateral to the

rectum and urethra which it helps to supply in addition to the levator ani muscle, anal glands, and finally appears at the doral base of the penis where it divides into: a) the dorsal artery 2£ the penis (N, fig. 9), and b) the deep

artery'gf the penis (artery_gf the corpus cavernosum). The

dorsal artery of the penis travels along the dorsolateral side of the penis on its respective side; whereas the deep artery of the penis runs within the corpus cavernosum.

B. THE PARIETAL BRANCHES:

a) The Obturator Artery (N, fig. 11) is the most

ventral component of the hypogastric trunk. It is one of the terminal branches of the trunk; the internal pudendal commonly being the other, as shown in fig. 11. The obturator artery remains superficial in the ventral plane and divides 57. dichotomously into: 1) the medial branch, and 2) a lateral branch (M, fig. 11).

1) The medial branch traverses in a mediocaudal direc-

tion to the side of the rectum where it is called the middle haemorrhoidal artery. In the female, the medial branch

supplies the wall of the vagina.

2) The lateral branch closely parallels the external

iliac deep within the pelvic cavity to pass with the vein through the obturator foramen to reach the adductors of the leg. Below the level of the acetabulum, it contributes to an anastomosis about the hip joint. Other branches are sent towards the pubic symphysis to supply muscles in that general area.

b) The Lateral Femoral Circumflex artery (G, fig. 11) arises from the dorso-lateral surface of the hypogastric trunk close to its termination. It traverses laterad to leave the pelvic cavity to cross the tendon of the rectus femoris muscle deep to the iliopsoas. It finally branches rather extensively to supply the muscles vastus lateralis, rectus femoris, tensor fascia, latae, and adjacent portions of the deep muscles of the back. Immediately after passing ventrad to the tendon of the muscle rectus femoris, the lateral femoral circumflex usually sends off a constant branch under the tendon of the rectus femoris across the neck of the femur to branch profusely to supply surrounding tendons, muscles, and contribute to the general anastomoses about the joint. FIGURE 11. The iliac vessels.

abdominal aorta middle caudal common iliac inferior vena cava inferior mesenteric superior gluteal lateral femoral circumflex internal iliac external iliac pudic-epigastric trunk femoral superior vesicular lateral branch of obturator obturator internal pudendal inferior branch of superior gluteal

superior branch of superior gluteal @WOZBHNMHCCQWWUOIZD> '9

o

[l l

l

>

MNIMII

wmnfl"

x.

\'

FIGURE 11 . 60.

c) The Superior Gluteal Artery (F, fig. 11) usually

arises from the dorsal surface of the common iliac as shown

in figure 11. In some specimens it branches directly from the hypogastric. The inconsistency of its origin, like that of the internal pudendal, is due to the variation in the embryological splitting between the external iliac and the hypogastric trunk. From its origin, which is covered by the common iliac artery, the superior gluteal parallels the hypogastric artery and is separated from it by the hypogastric vein. Immediately after the artery leaves the pelvis cavity, through the greater sciatic notch, it divides into: 1) superior branch which crosses

dorsad to the sciatic nerve to travel anteriorly (craniad) to supply the muscles in the region of the gleuteus medius, and 2) the inferior branch is the caudal continuation of

the main stem. It runs posteriorly along the tail muscles to send off branches to those muscles and the muscles in the dorsoposterior region of the thigh. The terminal portions of this artery continue into the fat around the anal glands and rectum, where it gives rise to superficial branches which pass to the skin before it finally runs along the lateral surface of the tail. FIGURE 12. Branches of the coeliac axis.

abdominal aorta left gastric (coronary) lienal anterior lienal stem posterior lienal stem lienogastric gastroepiploic hepatic gastroduodenal coeliac axis pyloric superior pancreaticoduodenal inferior pancreaticoduodenal

EUNQHEQWWUOCUP 62.

(' ‘

u. \ I r I 1 H r"i ‘ I z' ,9 “ I I Y I 'l

I ‘ I II I ‘ ‘ H 1:, IV" H ‘ C ‘ ul t I J W ’1 t I" \ . ‘ "’l' ‘ ‘

-" \ a 0' \ ' ’ “s ‘

H I! .I u ‘r ‘\\

L " U" ~‘ \ \

\ 'l \\ ° 4 .'

1 cm.

i 7' ' _ _ a-

FIGURE 12. 63.

II. THE VISCERAL BRANCHES OF ABDOMINAL AORTA

A) The Coeliac Axis (artery) (J, fig. 12) is the most

superior branch of the abdominal aorta. It arises from the ventral surface of the aorta close to the base of the crura of the diaphragm at the level of the left adrenal gland.

The trunk of the coeliac artery is less than 10 mm. in length. It projects ventrad before dividing into three main branches: the lienal, the left gastric, and the

hepatic arteries.

a) The Lienal (Splenic) Artery (0, fig. 12) is the

extreme left branch of the coeliac axis. It passes to the left for a short distance as a common trunk before dividing dichotomously into the posterior and the anterior

lienal stems. l) The posterior lienal stem (E, fig. 12) is demon-

strable as a direct extension of the main lienal stem.

It traverses sinistrad in the posterior wall of the greater omental bursa to distribute many small branches to the pancreas, the greater curvature of the stomach within the gastro-lienal ligament, and terminal branches to the posterior portion of the Spleen. 2) The anterior lienal stem (D, fig. 12) also gives

rise to pancreatic branches, branches to the greater curvature of the stomach via the gastro-lienal ligament before terminating in the anterior portion of the spleen. b) The Left Gastric (Coronary) Artery (B, fig. 12)

leaves the coeliac in a middle position between the splenic 64. and the hepatic arteries, in close apposition with the hepatic artery near its origin. It passes cephalo-laterad towards the lesser curvature of the stomach, where it forks to form numerous branches which supply both the lesser and the greater curvatures of the stomach as shown in fig. 12. c) The Hepatic Artery (H, fig. 12) passes cranioventrad

towards the hilus of the liver in very close apposition with the portal vein and the common bile duct. Interlobular branches of these three vessels are frequently referred to by histologists as "The portal trinity." Tissues forming the ventral boundary of the foramen epiploicum

(foramen of Winslow) invest these three vessels. Approx- imately mid—way in its course, the hepatic artery gives rise to the gastroduodenal artery (I, fig. 12) which courses

posteriorly to divide into three branches as follows:

1) The pyloric artery (K, fig. 12) passes directly

to the region of the pyloric sphincter before it traverses along the lesser curvature of the stomach to supply the gastric wall and to finally anastomose with the gastrica sinistra (left gastric) artery.

2) The pancreaticoduodenal superior artery (L, fig. 12)

passes dorsad to the horizontal first portion of the duodenum to take a position between the duodenal part of the pancreas and the duodenum proper. It gives rise to many branches which pass to both the pancreas and the duodenum. Finally it anastomoses with the pancreaticoduodenal inferior (M), a

branch of the superior mesenteric artery. FIGURE 13. Branches of the superior (anterior) mesenteric artery.

A. superior mesenteric B. middle colic C. right colic D. ileocolic E. inferior (posterior) mesenteric F. left colic G. superior haemorrhoidal H. intestinal

cecum ascending colon transverse colon descending colon small intestine (sectioned) ileum

401.4:me

FIGURE 13 . 67.

3) The gastroepiploic (G, fig. 12) passes dorsad to

the pylorus to reach the greater curvature of the stomach where it travels sinistrad to supply the gastric wall and

finally anastomoses with branches of the lienal arteries

(lienogastric, F) which supply the greater curvature of the

stomach.

The hepatic artery proceeds through Glisson's capsule

to send numerous branches to the lobes of the liver, and

a small cystic artery to the gall bladder.

B) The Anterior (Superior) Mesenteric Artery (A,

fig. 13) arises from the ventral side of the dorsal aorta

approximately 1 cm. caudad of the-coeliac axis. It

passes caudoventrad to distribute its branches to the

caudal portion of the pancreas, the ascending and trans-

verse colon, and the small intestine.

Branches: a) Middle colic (colica media) b) Pancreaticoduodenalis inferior

c) Ileocolica d) Right colic (colica dextra)

e) Intestinal branches

Before giving the details of the superior mesenteric branches, it might be well to point out the unique arrange- ment of the colon of the fox squirrel. This mammal possesses

an unusually long colon; having a short mesentery between

the ascending and the transverse portions, and between

the transverse and cephalad portion of the descending colon. This results in two finger—like projections 68. extending cephalolaterad when the mesentery is stretched out as shown in figure 13. The projections are actually longer than those shown in the figure. a) The Colica Media (middle colic) (B, fig. 13) is

the first branch arising from the superior mesenteric artery, to supply the transverse and descending portions of the colon. Branches on the right surface anastomose with branches of the right colic; and those of the left surface anastomose with the colica sinistra from the inferior mesen- teric artery.

b) The Pancreaticoduodenalis Inferior is given off

from the dorsal right side of the superior mesenteric, to distribute its many branches to the posterior portion of the pancreas and the duodenum where it anastomoses with the pancreaticoduodenalis superior from the coeliac axis

as explained previously. c) The Ileocolic (D, fig. 13) passes to the extremely

large caecum to supply the ileocecal valve and the caudal end of the ileum. Caudad it anastomoses with the intestinal branches of the anterior mesenteric artery; craniad it anastomoses with the right colic artery. d) The Right Colic (C, fig. 13) passes to the ascend-

ing and the transverse colon, to anastomose with the ileo-

colic and the middle colic arteries. e) Numerous Intestinal Branches (H, fig. 13) are

given to the small intestine. Typically the terminal branches anastomose, to form marginal arches within the mesentery from which diffuse branches are given to supply

the intestinal wall.

divides metrically usually The passes renal. gives Accessory artery In Suprarenal to and copious fig. arises appear the gastric ing latter stant (F, addition, anastomose upon former fig. colon the E) D) The C) 13) branch off directly towards travels to (F, blood artery. right The at into The The The adrenal arises this 13), be to small Inferior branch arranged. Artery fig.7 the left

Left more anastomose from Inferior the Posterior two with abundant inferior and supply. caudad the level branches from from

branches; right glands adrenal ) active Superior passes the is the the Suprarenal arises colon a the the of

The along Suprarenal aorta superior middle blood branch Perhaps inferior suprarenal (Inferior)

with of the gland, aorta, ventral and for to craniad primary from

Sciurus Suprarenal the which right the the excitable a the supply. haemorrhoidal Artery of

haemorrhoidal the short the left but however, phrenic posterior adrenal Arteries along the colica side

Mesenteric arises left iliolumbar the fact niger left colic the right distance (E, writer Artery of may inferior the

Right media, renal gland. artery that from receives appear fig. the wall also (colic

medial renal have of has dorsal artery artery. Artery these (B, 7). Superior and artery, the are and the of (A', to suprarenal some named artery. fig. sinistra) right then a the side hypo— have asym- animals the fig. aorta (G). con~ (E, bear— 7) colon It the of a

7) (Ti \0 70.

F) The Internal Spermatic Arteries (O) are paired

vessels given off from the aorta at inconsistent levels.

The left internal spermatic artery arises from the ventral side of the aorta; the right vessel from the right lateral side usually at a higher level. The course of the arteries is diagonally latero-caudad to pass through the inguinal canal, along with the internal spermatic vein and the vas deferens to form a part of the spermatic cord. The artery travels into the scrotum to supply the dartos muscle, vas deferens, testes, epididymis, and the connective tissue of the scrotum.

G) The Ovarian Arteries in the female have the same origin as the internal spermatic arteries of the male. They cross the ureter ventrally on each side to traverse the ovarium where each supplies the ovary and sends branches to anastomose with the uterine arteries. FIGURE 14. Vessels of the lower extremity, medial aspect.

external iliac pudic-epigastric trunk femoral rami musculares saphenous artery saphenous magna vein plantar branch superficial circumflex iliac highest genicular dorsal branch

meQOmUOwb communicating branch

adductor longus muscle gracilis medial head of gastrocnemius iliopsoas femoral nerve

mmzwmw tibia 72.

/

, ,/,,x.

.

.

/fl,/

.

if

.

a

‘

r ..

\\

1 cm.

FIGURE 14 .

73.

E. The Lower Extremity

The Femoral Artery (C, fig. 14) is located on the medial

surface of the thigh as a direct continuation of the external iliac artery. It is bounded proximad by the inguinal liga- ment; distad it disappears from view as it approaches the popliteal fossa.

Branches: a) Superficial circumflex iliac

b) Rami musculares

c) Superficial epigastric

d) Articularis genu suprema (highest genicular)

e) Saphenous a) The Superficial circumflex iliac (H, fig. 14) is a

large muscular branch given off from the lateral surface of the femoral artery as it passes over the ventral base of the iliopsoas muscle. b) Rami musculares (D, fig. 14) consists of a variable

number of small vessels which leave the femoral artery as it progresses distally along its course. The point of entrance of the most anterior vessels in this group is covered by the femoral vessels when examined from the medial surface. These are deep branches, in the region of the superficial circumflex iliac, supplying the muscles pectineus, iliopsoas, vastus lateralis, rectus femoris, and the vastus medialis.

c) The Superficial epigastric is a thin artery arising

from the posterior surface of the femoral at approximately 74. one-half its course along the surface of the thigh, i.e. immediately before the femoral turns deep into the thigh. d) The Articularis genu suprema (highest genicular)

(I, fig. 14) arises from the femoral shortly beyond the point where the artery leaves the medial surface of the thigh to traverse deep towards the pOpliteal space where it becomes the popliteal artery. It runs deep to the super- ficial muscles as shown in fig. 14. e) The Saphenous Artery (E, fig. 14) leaves the femoral

artery just distad to the superficial epigastric. It ex- tends distad along the medial surface of the leg immediately adjacent to the saphenous nerve and the saphenous magna

vein (F). At the level of the patella, several small super- ficial branches leave the saphenous to pass anterior to the region of the knee joint. The distal portion of the saphenous forks to form the following:

1) dorsal branch 2) communicating branch

3) plantar branch

1) At approximately the midpoint of the shank the dorsal branch (J, fig. 14) of the saphenous can be seen to

leave the artery to traverse distad across the medial naked surface of the tibia. At the level of the tarsals it divides, to anastomose freely with the dorsal artery gr

the foot (2, dorsalis pedis), which is a continuation of the

anterior tibial artery. The main distal extension crosses

over the tendon of the muscle tibialis anticus and then in the metatarsal region it divides to form vessels which 75.

extend along the lateral and medial surfaces of the phal-

anges.

Distad to the origin of the dorsal branch, the saphenous

forks to form a posterior plantar branch and a middle com-

municating branch.

2) The communicating branch (K, fig. 14) in its course

along the medial surface of the leg parallels the dorsal

branch before disappearing from view between the tibialis

posticus and the tibia. It encircles the distal end of

the tibia to appear deep to the annular ligament, where it

participates in the blood supply of the dorsal portion of

the foot. 3) The plantar branch (G, fig. 14) runs along the

medial surface of the plantaris muscle and the achilles

tendon to pass behind the medial malleolus and continue

- unto the sole of the foot, where it forks to supply those

muscles on the ventral surface of the phalanges. Abundant

anastomoses connect this branch with the dorsal branch.

The Popliteal Artery (D, fig. 15) is described as that

portion of the femoral within the popliteal fossa. It is a

rather short artery, extending from point where the femoral

artery enters the popliteal fossa immediately above the

medial epicondyl of the femur bone, to the point where it

divides into the rural and the tibio—peroneal stems.

l) Branches of the Sural Stem:

a) Superficial sural

b) Femoropopliteal

0) Internal and external sural

d) Genicular FIGURE 15. Vessels of the pOpliteal fossa, medial aspect.

superficial sural artery posterior saphenous vein femoropopliteal popliteal sural stem genicular tibio-peroneal stem anterior tibial posterior tibial

internal sural WMHEQ’UWUOWP external sural

medial head of gastrocnemius muscle popliteal lymph node tibial nerve bowl-4 77.

FIGURE 15. 78.

a) The Superficial Sural Artery (Cutaneous gr Posterior

Saphenous) (A, fig. 15) is the principal artery of the sural

stem. It accompanies the posterior saphenous vein distad

along the lower leg lying between the lateral and medial

heads of the gastrocnemius muscle. Throughout its course,

small cutaneous branches are given off, and as the artery progresses behind the lateral malleolus, small tarsal branches

can be seen to arise from the artery. The artery extends

along the dorso-lateral side of the foot to anastomose with

the g. dorsalis pedis and contributes to the blood supply

of the fourth and fifth phalanx.

b) The Femoropopliteal Artery (C, fig. 15) leaves the

posterior surface of the sural stem to pass upward and

laterad to send branches to the lateral and posterior muscles

of the thigh and ultimately distribute superficial branches

to the lymph node of the popliteal space and the skin.

c) The Internal and External Sural Arteries (J & K, fig.

15) are rather small variable arteries usually arising from

the sural stem opposite the origin of the femoropopliteal artery. The external sural supplies the lateral head of the

gastrocnemius and adjacent muscles about the wall-of the popliteal space; while the internal sural traverses primarily

to the medial head of the same muscle.

d) The Genicular Arteries are those vessels leaving

the sural stem which extend laterally to form an intricate

anastomoses with the medial coursing vessels of the tibio- peroneal stem (F, fig. 15). 2) Branches of the Tibio-peroneal Stem:

The tibio-peroneal stem is that portion of the popliteal

artery which lies between the condyles of the femur within

the popliteal fossa. Just distad to its origin from the

popliteal, it forks to form the posterior and anterior tibial

arteries. a) The Posterior Tibial Artery (I, fig. 15) extends

distad between the medial head of the gastrocnemius and the underlying popliteus and tibialis posticus muscles. In man the vessel passes distally in the foot (Gray, 1936, p. 633), but in the squirrel it is confined to the shank where it

terminates by distributing numerous branches to the popliteus,

tibialis posticus, and the medial head of the gastrocnemius muscles. b) The Anterior Tibial Artery (H, fig. 15) is lost to

view as it passes beneath the popliteus muscle to reach the

lateral portion of the shank. Medial to the neck of the

fibula, it gives off two opposing branches as follows: 1) anterior tibial recurrent 2) peroneal artery 1) The anterior tibial recurrent artery is the most

anterior of the three arteries extending down the shank.

It courses anteriorly to pass over the anterior surface of

the fibular head to reach the knee immediately distad to the

patella where it anastomosis with the genicular arteries. 2) The peroneal artery arises from the anterior tibial

artery medial to the neck of the fibula to pass diagonally in

a posterio-mediad direction to follow the posterior groove of 80. the tibia for approximately a third of the bone's length

Where the primary stem enters the bone by way of the nutrient foramen.

After giving off the above two branches, the anterior tibial artery proceeds distad along the lateral portion of

the shank where it comes to the surface in the distal third

of the lower leg. It then continues superficially onto the dorsum of the foot where it ends as the artery dorsalis pedis

(dorsal artery_gr the foot).

81.

V. THE VENOUS SYSTEM

Introduction:

A vein and artery bearing the same name usually follow the same course. In most Specimens, the small veins were not injected so satisfactorily as the small arteries.

Special emphasis will be given to those veins which do not parallel the corresponding artery and also to those which deviate from the course of the artery. If additional information about a vein is desired, it is suggested that the reader consult the text material on the artery of the same name. In the figures given, a label may point to an artery which parallels a vein. It should be understood that the name of the artery and the adjacent vein is the same. 82.

A. The Thorax

The two Venae Cavae Superiores (M & V, fig. 1) are formed

by the union of the internal jugular and the subclavian

veins at the level of the first rib. They course caudad

towards the heart as shown in fig. 1. Both vena cavae enter the right atrium. The right superior vena cava is

shorter, entering the anterior portion of the right atrium.

The left vein is longer, crossing ventral to the aortic

arch, the root of the left lung, pulmonary vessels, and

bronchus to enter the posterior portion of the atrium on

the dorsal side in close proximity to the inferior vena

cava.

In the cat, which has only one superior vena cava, the

numerous coronary veins coming from the heart wall, enter

the coronary sinus which runs along the dorsal surface of

the heart in the sulcus coronarius. The sinus, which is a

remnant of the proximal portion of the former left precaval,

opens directly into the left posterior corner of the right

atrium (Hyman, 1947, p. 378).

There are two superior vena cavae in the squirrel, as

there are in the rat (Hunt, 1924, p. 59), in contrast to the cat which has only one superior vena cava (Reighard, 1940).

From a taxonomic point of view, this is of interest if one

realizes the fact that the fox squirrel, the domestic cat,

and the Norwegian rat belong to the same class, Mammalia;

but the cat belongs to the order Carnivora, whereas the rat

and the squirrel belong to the order Rodentia. The anatomical

difference cited may be a characteristic of the order. 83.

The Pulmonary Veins are formed at the root of each

lung by the confluence of veins from the lung lobules. They are multiple veins which pass from the lung to enter the right atrium. Those from the right side pass dorsal to the right superior vena cava and are crossed by the curve of the azygos vein as it enters the right precava. The left pulmonary veins pass with the artery between the aorta and the left precava.

The Internal Mammary Vein (0, fig. 1) originates in the

ventral lower thoracic body wall. Two stems parallel the sternum, one on each side, to follow the correSponding artery. At the level of the second rib, the left stem cuts across the sternum to join the right and form a single trunk which enters the right superior vena cava at the level of the first intercostal Space.

The Azygos Vein lies on the dorsal body wall of the

thorax to the right of the dorsal aorta and vertebral column. In the rat the azygos vein lies on the left side (Hunt, 1924, p. 53). In the cat the azygos vein is found on the right side (Reighard & Jennings, 1940, p. 316), as it is in man (Gray, 1936, p. 663), and the squirrel. The exact origin of the azygos was difficult to determine with a great degree of certainty because of insufficient in- jection material, but the twelfth intercostal veins unite to the right of the aorta to appear as the origin of the azygos vein. The vein receives the intercostals from both sides as it proceeds anteriorly in its dorsal position before it terminates by bending ventrad to enter the right 84. superior vena cava. The superior intercostal could not be found to enter the azygos. Greene (1935, p. 225) maintains that the superior intercostal vein in the rat collects blood from the most anterior three intercostal spaces in the right thoracic region, and possibly two intercostal spaces in the left. This vein corresponds to the costocervical trunk, but no such vein could be positively identified in any of the squirrel specimens studied.

The Intercostal Veins follow the course of the inter-

costal arteries to enter the azygos vein as described above. 85.

B. The Upper Extremity

The Cephalic Vein (J, fig. 3) is formed by a number of

small tributaries which pass to the radial side of the wrist. It passes along the radial side of the arm to the deltoid region where it accompanies the acromiodeltoid artery before entering the external jugular vein above the clavicle.

The Brachial Vein drains the deep portion of the arm.

Its tributaries correspond in position and name to the branches of the brachial artery. The Axillary Vein (E, fig. 2) is the proximal contin-

uation of the brachial vein. It accompanies the axillary artery and its branches Join the external Jugular to form the subclavian vein.

Tributaries: l) circumflexo-subscapular

2) lateral thoracic 3) anterior thoracic (thoraco—acromial)

Each of the above three tributaries follows its cor- responding artery. The Subclavian Vein (A, fig. 2) is formed by the union

of the axillary and the external Jugular veins at approx- imately the level of the first rib. 86.

C. The Head and Neck

A) The Superficial Veins of the Face and Head: a) Anterior facial b) Angular

c) Nasal

d) Supra-orbital

e) Posterior facial - f) Superficial temporal

g) Internal maxillary h) Pterygoid plexus a) The Anterior Facial Vein (D, fig. 5) is one of

the most prominent veins in the face of the squirrel. Its course and tributaries are essentially like the course and branches of the artery. For further details consult the description of the facial (external maxillary) artery.

The anterior facial vein extends posteriorly and ventrally along the border of the masseter muscle, to cross the mandible lateral to the facial artery before entering the groove between the masseter and the anterior belly of the digastricus muscles. In the cervical region it anas- tomosis with the posterior facial vein (C, fig. 5) to form the external jugular vein (A). b) The Angular Vein (K, fig. 5) is a tributary of the

anterior facial vein. It is formed by the union of the supra-orbital (N) and the nasal veins as shown in fig. 5. c) The Nasal Vein(L, fig. 5) receives blood from

tributaries in the nasal region. It courses upward and 87. posteriorly to form the angular vein by fusing with the supra-orbital as described above.

d) The Supra-orbital vein (N, fig. 5) originates above

the eye where its tributaries are closely associated with those of the superficial temporal. It runs forward and. downward to unite with the nasal vein to form the angular vein. e) The Posterior Facial Vein (C, fig. 5) is formed by

the union of the superficial temporal (R) and internal maxillary veins (S) ventrally and anteriorly to the external auditory meatus. The course of the vein is postero-ventrad to reach the cervical region deep to the parotid gland where it unites with the anterior facial vein to form the external fiugular vein (A).

The posterior facial vein receives the anterior auricular

vein (T), the vein from the pterygoid plexus (V), and the posterior auricular vein (U).

f) The Superficial Temporal Vein (R) originates near

the posterior periphery of the eye socket. It passes

postero-ventrad for a short distance and then unites with the internal maxillary to form the posterior facial vein (C).

The superficial temporal vein drains the temporal and

the postero—orbital region. It receives the orbital vein (Q)

from the eye socket, and the transverse facial vein (M) which

is in close proximity to the corresponding artery. g) The Internal Maxillary Vein (S) exhibits tributaries

which closely parallel the branches of the internal maxillary

artery. Its origin is deep to the temporal and masseter 88. muscles, Just anterior to the anterior auricular vessels.

It Joins the superficial temporal to form the posterior facial vein. The tributaries of the internal maxillary drain the temporal region, the inferior facial muscles of mastication, and also contribute to the makeup of the pterygoid plexus. h) The Pterygoid Plexus lies medial to the mandible

appearing to be made up of tributaries from every direction of the head and face. B) Veins of the Neck: a) External jugular b) Posterior external jugular c) Cephalic d) Transverse scapular e) Internal jugular f) Vertebral

(a) The External Jugular Vein (A, fig. 5) is formed by

the union of the posterior and anterior facial veins as described previously. In the cervical region the vein lies very superficial to cross the surface of the sternomastoid muscle and clavicle to unite with the axillary vein to form the subclavian. The point of fusion of the anterior and posterior facial veins is not constant so the length of the external Jugular vein is variable. b) The Posterior External Jugular Vein runs over the

shoulder deep to the clavotrapezius muscle to enter the external jugular vein on its lateral side. Tributaries of this vessel can be identified along the acromiospino trapezius and clavotrapezius muscles.

03 KO

0) The Cephalic Vein is located superficially as it

passes over the shoulder joint across the deltoid muscles to enter the external jugular vein very close to the termi- nation of the posterior external jugular. The cephalic vein is also discussed as a vein of the upper extremity. d) The Transverse Scapular Vein lies deep to the

cephalic to follow the course of the transverse scapular artery. Major tributaries can be seen which drain blood from the supraSpinatus, infraspinatus, and subscapularis muscles. The point of entrance into the external jugular vein is just caudad of the termination of the cephalic vein.

e) The Internal Jugular Vein is a thin vein located

in the cervical region lateral to the trachea along the common carotid artery and the vagus nerve. It passes in this position caudad to usually join the external jugular at the same level as the subclavian. These three vessels here form the superior vena cava (M & V, fig. 1).

f) The Vertebral Vein can be identified in the brain

region as it passes caudad along the lateral border of the myelencephalon and the spinal cord. The portion of the vein near its termination is located as it traverses post— erolaterad after having emerged from the sixth intervertebral space. The vein lies ventral to its artery, crosses it on the medial side to enter the venal cava superior dorsad to the internal jugular vein.

0) The Superficial Veins of the Brain:

a) Superior cerebral b) Inferior cerebral

FIGURE 16. Vessels of the brain, dorsal aspect.

inferior cerebral superior cerebral middle cerebral artery superior petrosal sinus inferior cerebellar superior sagittal sinus transverse sinus superior cerebellar

EQTIEIIIUOtIib 91.

FIGURE 16. 92.

c) Superior cerebellar

d) Inferior cerebellar

a) The Superior Cerebral Veins (B, fig. 16) are

numerous segmental veins which arise on the lateral portion of the cerebral hemisphere to pass mediad to enter the superior sagittal sinus almost at right angles, as shown in fig. 16. The anterior pair extend laterad to circum- scribe the frontal poles and appear on the ventral surface of the cerebral hemisphere where they anastomose with the inferior cerebral veins (F, fig. 16). b) The Inferior Cerebral Veins (A, fig. 16) have their

tributaries extending over the ventrolateral surface of the hemispheres. Anteriorly they connect with the superior cerebral veins (B, fig. 6); posteriorly, they appear to join at approximately the junction point of the petrosal and the transverse sinuses. c) The Superior Cerebellar Veins (H, fig. 16) arise

from small tributaries seen in the sulci on the surface of the cerebellum. These form two vertical parallel veins marking the lateral border of the vermis of the cerebellum which lead anteriorly to enter the transverse sinus. d) The Inferior Cerebellar Veins (E, fig. 16) can

best be seen in the grooves between the parafloccular and the lateral lobes of the cerebellum. They enter the trans- verse sinus. D) Sinuses of the Dura Mater:

The author feels that it is beyond the scope of this text to present a detailed study of the sinuses of the dura 93.

Tater. Thus consideration will be shown to only the sinuses which have been mentioned above in connection with the super- ficial veins of the brain. a) Superior sagittal (superior longitudinal) b) Transverse (lateral)

c) Superior petrosal a) The Superior Sagittal (Superior Longitudinal) Sinus

(F, fig. 16) lies on the antero-posterial midline on the dorsal surface following the line of the sagittal suture of the skull. Posteriorly it joins the transverse sinus. b) The Transverse Sinuses (G, fig. 16) begin in the

dorsal midline in the sulcus between the cerebellum and the hemispheres. The superior petrosal and the superior cere- bellar veins are chief tributaries of this sinus.

c). The Superior Petrosal Sinus (D, fig. 16) originates

anterior to the transverse sinus to appear along the dorso— posterolateral corner of the cerebral hemisphere where it meets the transverse sinus on its respective side as shown in fig. 16. FIGURE 17. The hepatic-portal system.

coronary pyloric lienal (Splenic) left colic middle colic intestinal portal pancreaticoduodenal gastroepiploic anterior (superior) mesenteric right colic

bp‘R‘C-JHCGQ'IJWUOUJb ileocolic

oesophagus stomach Spleen small intestine liver duodenum pancreas

OO-QCMU‘I-lrme cecum 95.

FIGURE 17 . 96.

D. The Hepatic Portal System

The hepatic portal system is composed of those veins which transport blood from the abdominal and pelvic diges- tive tract, spleen, and pancreas to the liver.

The Portal Vein (G, fig. 17) is the large vein which

transports blood from the abdominal digestive viscera to the liver. It is accompanied by the hepatic artery as it travels in a cephalad direction to enter the porta hepatis.

At the porta hepatis the vein can be seen to divide into interlobar veins.

There has been no special attempt by the writer to go into an exhaustive study of the blood supply of any one organ, which would involve a microscopic examination; but in passing it might be pointed out that in a gross cross-section of a liver lobe from a triply injected squirrel, one can see three colors of vessels. The yellow vessels are the hepatic portal vessels, i.e. branches of the portal vein, the blue vessels are the systemic veins (hepatic vein tributaries), and the red are the systemic arterial branches of the hepatic artery. Therefore, the blood enters the liver through two vessels: a) the portal vein, and b) the hepatic artery. The blood is transported from the liver to the posterior vena cava by the hepatic veins.

Tributaries of the Portal Vein:

a) Lienal b) Anterior (Superior) mesenteric c) Pyloric d) Gastroepiploic

e) Pancreaticoduodenal a) The Lienal (Splenic) Vein (C, fig. 17) originates

by fine tributaries within the spleen. The vein parallels the artery because of two constant stems: the posterior stem which receives larger pancreatic tributaries, and the anterior stem which follows the corresponding arterial stem. According to Greene (1935, p. 227), in the rat the lienal vein receives a solitary pancreatic vein and the left gastroepiploic vein accompanies the artery of the same name. In the squirrel there is no definite left gastro- epiploic vein or artery following the greater curvature of the stomach. There are branches and tributaries (liengf gastrics) of the two stems of the lienal vessels which pass to the body of the stomach along its greater curvature as shown in figures 12 and 17.

Tributaries: 1) coronary

2) left colic 3) middle colic

4) pancreatic l) The coronary vein (A, fig. 17) originates along

the lesser curvature of the stomach on the dorsal and ventral sides to follow the course of the left gastric (coronary) artery. Dorsad to the pyloric portion of the stomach, the coronary vein enters the lienal about four or five milli- meters before the lienal joins the superior mesenteric vein. 98.

2) The left colic vein (D, fig. 17) follows the course

of the corresponding artery from the descending portion of

the large intestine. It usually enters the lienal vein

on its posterior surface to the left of the middle colic

termination. 3) The middle colic vein (E, fig. 17) follows the

course of the middle colic artery to usually enter the lienal

vein medial and parallel to the left colic.

The distance between the middle and left colic veins

at their points of entrance into the lienal is variable.

They may be fairly far apart or may join before entering

the lienal as a common trunk, as was the case in two speci-

mens studied. In one specimen the left and middle colic

‘ vessels united before entering the superior mesenteric

vein a short distance posterior to the lienal vein.

4) The pancreatic tributaries enter both stems of

the lienal vein as described above. b) The Anterior (Superior) Mesenteric Vein (J, fig. 17)

collects blood from all of the small intestine, caecum,

and a portion of the colon.

Tributaries: l) intestinal 2) ileocolic 3) right colic

l) The intestinal tributaries (F, fig. 17) are numerous

vessels collecting blood from the ileum and jejunum. They

accompany the branches of the anterior mesenteric artery,

which is also located in the mesentery. The numerous tributaries drain into a main stem which forms the left

terminal tributary of the anterior mesenteric vein. 2) The ileocolic vein (L, fig. 17) is the terminal

right stem of the anterior mesenteric vein, which collects blood from the caecum and region of the ileo-cecal valve. 3) The right colic (K, fig. 17) collects blood from

the ascending and right portion of the transverse colon. It

accompanies the right colic artery. 0) The Pyloric Vein (B, fig. 17) is a small vein

draining the pyloric portion of the stomach primarily in

the region of the pyloric valve and on the surface of the

lesser curvature. It enters the portal vein close to the

pancreaticoduodenal and the gastroepiploic veins. d) The Gastroepiploic Vein (I, fig. 17) collects blood

from the pyloric and lower body of the stomach on the sur-

face of the greater curvature. The vein passes dorsal to

the pyloric valve to contribute to the formation of the

portal vein as shown in figure 17. As was pointed out previously, there is no definite left gastroepiploic in the

squirrel as there is in some other mammals.

e) The Pancreaticoduodenal Vein (H, fig. 17) lies

between the head of the pancreas and the duodenum in close

apposition with its corresponding artery. The pancreatico- duodenal passes craniad dorsal to the first part of the duodenum to enter into the formation of the portal vein as

the extreme dextrad tributary. In two specimens studied,

the pancreaticoduodenal vein received the gastroepiploic

vein before entering the portal. 100.

E. The Abdomen

The Inferior Vena Cava (Post Cava) (X, fig. 1; D, fig. 11)

drains the visceral and somatic portions of the body posterior to the diaphragm. It is formed posteriorly by the junction of the two common iliac veins as shown in figures 7 and 11.

Near its origin it lies dorsad to the aorta; as it proceeds anteriorly, it comes to lie to the right side of the aorta, and as it pierces the diaphragm, it lies ventrad and to the right of the aorta. In the thoracic cavity, it ascends in a straight line opposite the right precaval to enter the right atrium at its posterior end.

Tributaries:

a) Lumbar b) Ilio-lumbar

c) Spermatic (male) d) Ovarian (female)

e) Renal

f) Inferior phrenic g) Hepatic The first four veins listed above, 1. e. a) the lumbar, b) iliolumbar, c) spermatic, and d) ovarian follow the arteries of the same names. e) The Renal Veins (G, fig. 7) leave the hilus of the

kidney ventrad to the renal arteries to pass mediad towards the inferior vena cava. The left vein is longer than the right and enters the vena cava at a lower level than the right. This is the reverse of the renal arrangement found 101. in man where the right kidney is located more caudad than the left (Gray, 1936, p. 674). The left renal vein in the squirrel also differs from man in not receiving the left internal spermatic or ovarian vein (of. fig. 7). g) The Hepatic Veins are variable in number and posi-

tion. They drain the liver to enter the inferior vena cava immediately caudad to the diaphragm. 102.

F. The Pelvis

The Common Iliac m (0, fig. 11; Q, fig. 7) arise distally in the pelvic region by the union of the external iliac and the internal (hypogastric) veins. They extend mediad to the common iliac arteries on the ventrolateral surface of the true pelvic cavity to reach the midline

Where they fuse to form the inferior (post) vena cava as

shown in fig. 11.

Tributaries: a) The Internal Iliac (hypogastric) Vein receives

tributaries corresponding somewhat to the branches of the internal iliac artery. All of the tributaries could not be followed with certainty. The stem is short and lies between the hypogastric and the superior gluteal arteries. 1) The Internal Pudendal Vein appears as a direct continuation of the hypogastric vein. It follows the course

of the artery to leave the pelvic cavity with the superior gluteal artery (cf. internal pudendal artery). 2) The Lateral Femoral Circumflex Vein lies on the

cephalic side of the lateral femoral circumflex artery.

Its tributaries are in close apposition to the branches

of the artery. b) The External Iliag_ygln follows the course of the

artery to collect the blood from the lower extremity. It

is an anterior continuation of the femoral vein which joins

the internal iliac vein to form the common iliac as stated

above. 103.

Tributaries: l) pudic epigastric trunk

2) obturator 1) The pudic epigastric trunk is demonstrable as a

large vein joining the external iliac next to the pudic epigastric artery. The tributaries of the vein could not be identified, except in the female where the superior external pudendal vein was seen to follow the artery of the

same name 0 2) The obturator vein arises in the region of the

hip joint where it follows the lateral branch of the ob- turator artery through the obturator foramen to enter the pelvic cavity. It leaves the artery to enter the external iliac vein less than a centimeter cephalad of the pudic- epigastric vein. c) The Superior Vesicular Vein (P, fig. 9) has its course similar to that of the superior vesicular artery. It can be seen to enter the common iliac close to its artery.

The superior vesicular vein has two tributaries as follows: 1) The inferior vesicular vein (I, fig. 9) runs close

to the inferior vesicular artery to collect blood primarily from the base of the bladder and the surrounding sex glands. 2) The differential vein (K, fig. 9) follows the vas

deferens and the differentialartery. d) The Superior Gluteal Vein could not be found in any specimen studied as a distinct vessel corresponding to the superior gluteal artery. In the rat, according to 104.

Greene (1935, p. 231), it is also normal not to have a distinct superior gluteal vein. The venous tributaries which accompany the branches of the superior gluteal ar- tery enter the internal pudendal vein. e) The Middle Caudal (Sacral) Vein (R, fig. 7) fol- lows the course of the middle caudal artery. Near its termination it lies on the left side of the artery as the vein enters the left common iliac near the origin of the post cava. 105.

G. The Lower Extremity

The Plantar Vein (G, fig. 14) is demonstrable just

medial to the calcaneus as it passes cephalad on to the shank to follow the plantar branch of the saphenous artery.

The Anterior Tibial Vein (H, fig. 15) follows the

course of the artery bearing the same name. The origin of the vein could not be located, but near its termination within the popliteal fossa it can be demonstrated medial to the neck of the fibula. Just before the anterior tibial vein turns towards the back of the knee, the peroneal vein

enters it. The anterior tibial vein, which follows the artery, crosses the head of the tibia to join the pgsterior

tibial vein (I, fig. 15) to form the tibio-peroneal stem (G).

This arrangement corresponds to that found in the arteries. The tibio-peroneal stem in turn joins the sural stems (E)

to form the popliteal vein (D).

The Femorgpopliteal Vein (C, fig. 15) drains the

femoral-popliteal artery region. The vein enters the sural stem (E) near its termination.

The Posterior (small) Saphenous Vein (B, fig. 15) fol-

lows the superficial sural artery lying between the lateral and medial heads of the muscle gastrocnemius. This vein is the largest tributary of the sural stem. The Popliteal Vein (D, fig. 15), as stated previously,

is formed within the popliteal fossa by the union of the tibio-peroneal and the sural stems. It is a very short vein, about equal in caliber to the femoral vein, and is located within the popliteal space. 106.

The Femoral Vein (C, fig. 14) is a direct continuation

of the popliteal vein. Upon leaving the popliteal Space, it runs deep along with its artery to appear on the medial surface of the thigh at approximately its midpoint. On this surface, it accompanies the femoral artery to course up- ward to leave the thigh by passing under the inguinal ligament, beyond which point it is known as the external iliac vein.

Tributaries: a) The Saphena Magna Vein (F, fig. 14) follows the

saphenous artery to enter the femoral vein as it appears on the medial surface of the thigh.

b) The Superficial Circumflex Iliac Vein accompanies

the corresponding artery. 107.

VI. LIST OF REFERENCES

Arey, L. B. 1947. Developmental Anatomy. w. B. Saunders Co., Philadelphia. Burt, w. H. 1946. The Mammals of Michigan. The University of Michigan Press, Ann Arbor, Michigan. Crabb, E. D. 1946. Principles of Functional Anatomy of the Rabbit. John S. Swift Co., St. Louis. Grant, J. C. 1946. A Method of Anatomy. Williams and Wilkins Co., Baltimore. Gray, H. 1936. Anatomy of the Human Body. Lea and Febiger, Philadelphia. ' Greene, E. C. 1935. Anatomy of the Rat. Transactions of the American Philosophical Society. Philadel- phia. Hamilton, W. J. 1945. Human Embryology. The Williams & Wilkins Co., Baltimore, Md. Hunt, H. R. 1924. A Laboratory Manual of the Anatomy of the Rat. The Macmillan Co., New York.

Hyman, L. H. 1947. Comparative Vertebrate Anatomy. University of Chicago Press, Chicago, Illinois.

Johnston, T. B. 1945. A Synopsis of Regional Anatomy. Lea & Febiger, Philadelphia.

Maximow, A. A. 1947. A Textbook of Histology. w. B. Saunders Co., Philadelphia.

Orwoll, H. S. 1940. Osteology and Myology of the Fox Squirrel, Gray Squirrel, and the Red Squirrel. Michigan State College Thesis, for the Doctor of Philosophy degree. Reighard, J. and Jennings, H. S. 1940. Anatomy of the Cat. Henry Holt and Co., New York.

Romer, A. S. 1950. The Vertebrate Body. W. B. Saunders Co., Philadelphia. Storer, T. I. 1943. General Zoology. McGraw-Hill Book Co., Inc., New York. 108.

VII. CURRICULUM VITAE

Thomas William Jenkins was born in Adrian, Michigan, in 1922. His early education was obtained in Ohio, where he was graduated from Chaney High School in Youngstown in

1940.

In 1947 he was graduated from Kent State University in

Ohio with a Bachelor of Science degree. While at that institution, he was an undergraduate assistant in the

Department of Biology, where his major field of study was zoology.

At the present time he is a graduate assistant in the

Zoology Department at Michigan State College, where he is a student in zoology and anatomy. y.

.5.» 9w 1"» “I 2 \ 3 "‘r I u...’ iii-r: 4“"“1 Al 19 at”

-1 (>“\ no 0 ' is .4

HICHIGRN STQTE UNIV. LIBRQRIES

31293100737919