The Arterial System of the Head and Neck of the Rhesus Monkey with Emphasis on the External Carotid System ' WALTER A. CASTELLI AND DONALD F. HUELKE Department of Anatomy, The University of Michigan, Ann Arbor, Michigan ABSTRACT The arterial plan of the head and neck of 64 immature rhesus mon- keys (Macacn mulatta) was studied using four techniques - dissection, corrosion preparations, cleared specimens, and angiographs. In general, the arterial plan of this area in the monkey is similar to that of man. However, certain outstanding differ- ences were noted. The origin, course, and distribution of all arteries is described as well as the vascular relations to pertinent structures. As has been mentioned previously 10% formalin except 17 which were un- (Dyrud, '44; Schwartz and Huelke, '63) embalmed. Four different techniques were the rhesus monkey is useful for many used for the study of the arterial distribu- types of medical and dental investigations, tion : ( 1 ) dissections - 27 specimens; (2) yet its detailed gross morphology is virtu- corrosion preparations - 6; (3) cleared ally unknown. Although certain areas of specimens - 15; (4) angiographs - 16 the monkey have been studied in detail - heads ( 11 unembalmed and 5 embalmed). brachial plexus, facial and masticatory The arterial system of the specimens used musculature, subclavian, axillary and cor- for dissection was injected with vinyl ace- onary arteries, orbital vasculature, and tate, red latex, or with a red-colored gela- other structures (Schwartz and Huelke, tion mass. For the dissection of smaller ar- '63; Chase and DeGaris, '40; DeGaris and teries, the smallest of 150 ~1 in diameter, Glidden, '38; Chase, '38; Huber, '25; Wein- the binocular dissection microscope was stein and Hedges, '62; Samuel and War- used. The corrosion specimens were pre- wick, '55; Eyster, '44; Wagenen and Catch- pared by injecting the arteries with vinyl pole, '56; Tokarski, '31; Kennard, '41). acetate followed by maceration of the soft other areas have been virtually overlooked tissue with potassium hydroxide (3-10% ) or have received but passing attention. for 24 to 72 hours. The dye selected for The literature on the arterial supply of the injection of the cleared specimens was primate head has been adequately sum- Teichmann's paste (Teichmann, '52) marized by Dyrud ('44). Very few in- colored with cinnabar. These specimens vestigators, however, have used Macaca were decalcified in 4% nitric acid and then mulatta specimens and more importantly cleared by the Spalteholtz method. The in most of the articles only brief descrip- radiopaque material for the angiographs tions have been presented with many of was the modified Schlessinger's mass the pertinent morphological details not (Reiner and Rodriguez, '57), the main having been stated, or overlooked. Addi- components being mercury and barium tionally, only a few specimens have been sulfate. used in the majority of these works. It is The head and neck was removed from our purpose to present the arterial plan of the animal at the level of the clavicles or, the head and neck, especially that of the in some cases, a V-shaped section was external carotid arterial system. made with the apex extending down to the arch of the aorta. Both common carotid MATERIALS AND METHODS 1 This investigation was supported (in part) by USPHS research grant DE-00895 from the National Sixty-four immature rhesus monkeys Institute of Dental Research, National Institutes of (Macaca mulatta) were used for this study. Health, Bethesda, Maryland. 2 Present address: Department of Anatomy, Univer- All of the animals were embalmed with sity of Concepcion, Concepcion, Chile. AM. J. ANAT., 116: 149-170. 149 150 WALTER A. CASTELLI AND DONALD F. HUELKE arteries, or the left common carotid artery rior mediastinum and as it leaves the thor- and the brachiocephalic arterial trunk acic cavity, it is crossed by the left brachio- were cannulated depending on the individ- cephalic vein. ual situation; paraffin (Castelli, '63) or At the base of the neck, the common dental stone was applied to the cut surface carotid arteries are less than 1 cm apart. to provide adequate vascular resistance so They diverge from one another through that the injected material would pass their course in the neck, and, at the level through the arterial channels and not of the carotid bifurcation, they are 3 cm seep out through the exposed tissue. Photo- apart. The common carotid artery is graphs of all stages of dissection were covered by the sternomastoid muscle and taken, as well as of many of the corrosion lies medial to the internal jugular vein and cleared specimens. with the vagus nerve behind and between them. At approximately the mid-neck level, OBSERVATIONS the common carotid artery is crossed by Common carotid arteries. Minor vari- the omohyoid muscle, and the artery is ations as to the origins of the common tightly bound to the posterior surface of carotid arteries were found. Most often a the lateral lobe of the thyroid gland. The trunk, averaging 7 mm in length, arises common carotid artery divides into the ex- from the apex of the aortic arch and is the ternal and internal carotid arteries approx- origin to the left common carotid artery imately 1 cm above the angle of the man- and the brachiocephalic artery. At times dible (fig. 3). The bifurcation of the a very short common trunk is found; how- common carotid artery is 4 to 5 cm above ever, on sectioning the aorta, it is noted the level of the sternoclavicular joint. that both vessels have independent open- External carotid artery. At the carotid ings separated only by a thin septum. Of bifurcation the external carotid artery is 32 specimens studied, the left common anterior and only slightly lateral to the carotid artery and brachiocephalic trunk internal carotid artery. The internal caro- arose separately from the aortic arch in tid artery is tightly applied to the lateral only one animal (figs. 1 and 2). wall of the pharynx by the posterior di- The common trunk passes anterior to gastric muscle. The external carotid artery the left side of the trachea; between the runs parallel to the internal carotid artery superior vena cava on the right and the for approximately 1 cm, then passes be- left subclavian artery, left vagus nerve, tween the stylohyoid and posterior digas- and left phrenic nerve (fig. 2). tric muscles. Above the posterior digastric The brachiocephalic artery has an ob- muscle it swings laterally and passes ob- lique upward course across the front of liquely upward through the parotid gland the trachea and averages 16 mm in length. toward the posterior border of the ramus It is covered by the left brachiocephalic of the mandible reaching it slightly be- vein, or the superior vena cava, and by neath the condylar neck. Here the exter- adipose tissue of the superior mediasti- nal carotid artery continues forward, me- num. The brachiocephalic artery termi- dial to the ramus, as the maxillary artery. nates in the thorax by bifurcating into the Sometimes, at this point, a very small right common carotid and right subclavian superficial temporal artery is given off arteries (fig. 2). (fig. 3). The right common carotid artery has a 1. The superior thyroid artery is the short intrathoracic course (8 mm) ascend- first branch of the external carotild artery, ing along the right side of the trachea (fig. arising a few millimeters beneath the ling- 2). Close to the apex of the thorax it is ual-facial trunk, or as a branch of this covered by the origins of the sternohyoid trunk. The superior thyroid artery is found and sternothyroid muscles. inferior to the hypoglossal nerve and the The left common carotid artery passes posterior digastric muscle. The artery is directly upward through the thorax me- extremely short (approximately 5 mm in dial to and slightly behind the left vagus length) and fans out into several branches. nerve, adjacent to the left lung. It is One, a superior laryngeal branch, passes covered by the adipose mass of the supe- horizontally deep to the thyrohyoid muscle HEAD AND NECK ARTERIES IN RHESUS 151 Fig. 1 The common arterial stem (1) of the brachiocephalic trunk (2) and left common carotid artery (3) overlying the trachea (4). (Dissection preparation.) and perforating the thyrohyoid membrane, border of the lobe; the other, on the poste- supplies the upper part of the larynx. An- rior aspect of the lateral lobe (fig. 3). other branch continues downward to sup- 2. The lingual-facial trunk arises from ply other infrahyoid muscles. A terminal the anterior part of the external carotid branch passes to the medial side of the artery 1 or 2 mm beyond its origin. The thyroid lobe, and from it very small trunk passes forward and slightly upward branches arise to supply the isthmus of the deep to the posterior digastric muscle; thyroid gland and the upper part of the near its origin the hypoglossal nerve is trachea. One or two small thyroid ter- lateral to the trunk and further on the minal branches are given off at the level nerve passes deep to the trunk to reach the of the apex of the lateral lobe. One of tongue. The vessel continues forward for a these passes downward on the lateral distance of approximately 1 cm and di- 152 WALTER A. CASTELLI AND DONALD F. HUELKE Fig. 2 The large arteries in the upper mediastinum. The common arterial stem (1); brachiocephalic trunk (2); right subclavian artery (3); right common carotid artery (4); left common carotid artery (5); left subclavian atery (6); phrenic nerve (7); vagus nerve (8). (Dissection preparation.) vides into two main branches, the lingual The dorsal lingual branches are multi- and facial arteries (figs.