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. II. III. IV. VI. VII. CONTENTS Introduction..................................... Materials and Methods............................ The Heart.......,......... ...... ................. The Arterial System.............................. A. The Thorax................................... B. The Upper Extremity.......................... C. The Head and Neck............................ D. The Abdomen and Pelvis ....... ....... ..... .... E. The Lower Extremity.......................... The Venous System................................ A. The Thorax................................... B. The Upper Extremity.......................... C. The Head and Neck............................ a. The Superficial Veins of the Face and HeadOOOOOO.0.0.00.0.OOOOOOOOOOOOOOOOO b. Veins of the Neck........................ c. Superficial Veins of the Brain........... d. Sinuses of the Dura Mater................ D. The Hepatic Portal System.................... E. The Abdomen.................................. F. The Pelvis................................... G. The Lower Extremity.......................... List of References............................... curriculum VitanO0.0000000000000000000000000.... Page 0) CD l» h) l4 12 29 43 73 81 82 85 86 86 88 89 96 100 102 105 107 108 Fig. Fig. Fig. Fig. 10. ll. 12. 13. 14. 15, 16. 17. LIST OF ILLUSTRATIONS The heart, vessels of the thorax, and branches of the subclavian artery, ventral aspect................. The left axillary artery and its branches... Vessels of the upper extremity.............. Arteries of the head and neck, ventral aspeCtOOOOOCOOO0.0.0.0.000...0..00......O... Vessels of the head and neck, lateral aspeCtOOOOOOOOOOOOOOCOOOOOOOOOOOOOOOOOOOOOOO Vessels of the brain, basal aspect.......... Vessels of the abdomen...................... Right external iliac and femoral arteries, showing branches of the pudic epigastric trunkoo00000000...ooooooooooooooo00000000000 Blood supply of the male genitalia.......... Blood supply Of the testis and epididymis... The iliac vessels....... Branches of the coeliac axis................ Branches of the superior (anterior) mesenteric.’.C...’............OOCCOOOOO Vessels of the lower extremity, medial aspeCtOO00......OOOOOOOOOOOOOOOOOOOOOOOOO... Vessels Of the popliteal fossa, medial aspect....IOCOOCOCOOOOOOOOOOOOOOO0.0.0.0.... Vessels Of the brain, dorsal aspect... The hepatic-portal system................... Page 7 l9 23 28 33 39 42 47 51 54 59 62 66 72 77 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. mflmmxwmw xz 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 glandular ductus parot:ideus external auditory canal dentary geniohyoid parotid gland sternohyoid sternomastoideus ‘ , r. . f \ .3 5 \ en.“ \ . ’ \ EIT (I) moi-4mm U0 "3 m ”'0 0220!:th 28. 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 b 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) colon diaphragm right kidney ureter 42. I \ ‘ \ ,9, f 2 \ .‘ \ “. .l‘ ‘ / \ \~ 3 _ \‘ !.' ‘\\ ’ , V. Ti." \ “ ,1, C.—7 i. . ‘7‘” . _ . . J11 1" ' \ ’ \‘\ K / J ‘ 0h . t FIGURE 7 . {/ .J H. Q J___.," \ 5’ 1 cm. 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 o 1 cm. [,1 if!!!” 1 H l , v 'IIQH‘ L WWII'H'I '1. FIGURE 8 . 47. 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 inferior vena cava iliolumbar internal spermatic Inferior mesenteric common iliac superior gluteal internal iliac (hypogastric) inferior vesicular femoral deferential pampiniform plexus testicular dorsal artery of penis external iliac superior vesicular O O O O O O I O O O O anal gland penis testis colon vas deferens urinary bladder GUI-twmi-J "UOZZWWMHEQWWUOWD ‘/ 'I- FIGURE 9 . on: F] .. '3': t" HM HmO’lJ 51. 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 caput epididymis testis vas deferens corpus epididymis cauda epididymis U'I-P’UUNH @WUOWP FIGURE 10 . ..... A _ .B C .\ 1 S‘% ‘\ v.\.;. ”I, gust?“ u J\~;/ Ill"! " l 3‘ i 2 .L_Qm 54. 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. @WOZBHNMHCCQWWUOIZD> 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 FIGURE 11 . '9 \' wmnfl" MNIMII o [l l l > x. 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. EUNQHEQWWUOCUP 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 (' ‘ u. \ I r I H "i ‘ z' “ 1 r I ,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 ‘ I! .I ‘r H u ‘\\ L " " ~‘ U \ \ 'l \\ 4 \ ° 1 cm. FIGURE 12. 62. .' i 7' ' _ _ a- 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 d. 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. (Ti \0 C) The Posterior (Inferior) Mesenteric Artery (E, fig. 13) arises from the ventral side of the dorsal aorta usually at the level of the right iliolumbar artery. It passes towards the colon for a short distance and then divides into two branches; the left colic (colic sinistra) (F, fig. 13), and the superior haemorrhoidal artery (G). The former branch passes craniad along the medial side of the colon to anastomose with the colica media, and the latter travels caudad along the posterior wall of the colon to anastomose with the middle haemorrhoidal of the hypo— gastric artery. The adrenal glands of Sciurus niger appear to have a copious blood supply. Perhaps the fact that these animals appear to be more active and excitable may have some bear— ing upon this abundant blood supply. D) The Left Superior Suprarenal Artery (B, fig. 7) arises directly from the aorta, but the Right Superior Suprarenal Artery is a branch of the right renal artery. In addition, the right inferior phrenic artery (A', fig. 7) gives off small branches to the adrenal gland. E) The Inferior Suprarenal Arteries also are asym- metrically arranged. The primary left inferior suprarenal artery (F, fig.7 ) arises from the left renal artery, and the right inferior suprarenal arises from the right renal. The left adrenal gland, however, receives a con~ stant branch from the aorta which the writer has named the Accessory Inferior Suprarenal Artery (E, fig. 7). 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 communicating branch adductor longus muscle gracilis medial head of gastrocnemius iliopsoas femoral nerve tibia mmzwmw meQOmUOwb 72. 1! Wino... 4’ , I. I / . . . .Ifl/l/rcfl/ / .a _ 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. WMHEQ’UWUOWP bowl-4 superficial sural artery posterior saphenous vein femoropopliteal popliteal sural stem genicular tibio-peroneal stem anterior tibial posterior tibial internal sural external sural medial head of gastrocnemius muscle popliteal lymph node tibial nerve FIGURE 15. 77. 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 ileocolic oesophagus stomach Spleen small intestine liver duodenum pancreas cecum OO-QCMU‘I-lrme bp‘R‘C-JHCGQ'IJWUOUJb FIGURE 17 . 95. 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 u...’ iii-r: 4“"“1 Al 19 at” .4 (>“\ I -1 0 is no ' HICHIGRN STQTE UNIV. LIBRQRIES 31293100737919