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