Part 26

The pectoral and clavobrachial muscles have been cut and laid aside, their ends being shown; only a part of the nerves are exhibited. 1, M. clavobrachialis; 2, cut end of M. pectoralis major; 3, cut end of M. pectoralis minor; 4, M. biceps; 5, M. teres major; 6, M. epitrochlearis, partly cut and turned back; 7, M. latissimus dorsi,

## partly cut; 8, M. pectoralis minor; 9, M. pectoralis major; 10, short

portion of caput mediale of M. triceps brachii. _a_, branches of the thyrocervical axis to clavobrachial and clavotrapezius muscles; _b_, suprascapular nerve; _c_, first subscapular nerve; _d_, musculocutaneous nerve; _e_, median nerve; _f_, V. axillaris; _f_′, V. brachialis; _g_, A. axillaris; _g_′, A. brachialis; _h_, first anterior thoracic nerve, accompanied by the anterior thoracic artery and vein; _i_, V. subscapularis; _j_, large muscular branch (to subscapular muscle) of the subscapular vein and brachial artery; _l_, A. subscapularis; _l_′, A. circumflexa humeri anterior; _m_, radial nerve; _n_, ulnar nerve; _o_, medial cutaneous nerve; _p_, A. thoracica longa; _q_, _r_, second anterior thoracic nerve; _s_, V. longa thoracica; _t_, A. and V. thoracicodorsalis; _u_, A. profunda brachii; _v_, branch of brachial artery accompanying medial cutaneous nerve; _w_, branch of A. collateralis radialis superior; _x_, A. collateralis radialis superior; _y_, V. mediana cubiti; _z_, A. collateralis ulnaris.]

=A. thoracicodorsalis= (_t_).--This arises from the subscapular a short distance from its origin and passes across the teres major to the latissimus dorsi (7), giving branches to both these muscles and to the epitrochlearis.

=A. circumflexa humeri posterior.=--The posterior circumflex artery arises from the A. subscapularis close to the origin of the latter. It passes between the subscapularis muscle and the teres major, close to the border of the biceps, then between the lateral and long heads of the triceps. It gives off a branch to the inner surface of the spinodeltoid and acromiodeltoid, then passes distad to supply the lateral and long heads of the triceps.

4. =A. brachialis= (_g_′).--The brachial artery is the continuation of the axillary (_g_) into the arm beyond the origin of the subscapular (_l_). It passes along that side of the biceps which lies next to the humerus. It passes thus, accompanied by the brachial vein (_f_′) and median and ulnar nerves, through the bicipital arch and afterwards between the biceps (4) and the intermediate division of the medial head of the triceps to the supracondyloid foramen of the humerus, through which it passes with the median nerve to reach the concavity of the elbow. It gives off the following branches:

_a._ =A. circumflexa humeri anterior= (_l_′).--The anterior circumflex artery usually leaves the brachial near its origin (but may arise from the subscapular (_l_) or one of its branches); it passes to the biceps (4) near the origin of the latter and sends a branch proximad to the head of the humerus.

_b._ =A. profunda brachii= or superior profunda (_u_).--This arises from the first part of the brachial or it may come off from one of the branches of the axillary (e.g., the subscapularis). It passes along with the radial nerve onto the dorsal side of the humerus and supplies the triceps muscle. It also sends branches to the epitrochlearis (6) and latissimus dorsi (7).

_c._ =Rami musculares.=--Muscular branches are given off near the supracondyloid foramen to the biceps (4), epitrochlearis (6), and brachialis muscles. A nutrient artery leaves the brachial proximad of the supracondyloid foramen, either separately or in common with the muscular branches, and passes into the nutrient foramen at the junction of the middle and distal thirds of the shaft of the humerus, supplying the bone.

_d._ =A. collateralis ulnaris= (superior) (or A. anastomotica magna) (_z_).--This leaves the brachial artery just proximad of the supracondyloid foramen and passes to the convexity of the elbow, supplying the structures about the olecranon.

_e._ =A. collateralis radialis superior= (Fig. 130).--This rises from the axillary artery just proximad of the supracondyloid foramen (Fig. 122, _x_), in company with the vena mediana cubiti (_y_), passes across the surface of the biceps (4), beneath the pectoantibrachialis, into the concavity of the elbow. Here it gives branches to the pectoantibrachialis, clavobrachialis, and extensor muscles of the forearm. It then passes onto the ventroradial border of the forearm (Fig. 130) and runs along this border, in company with the vena cephalica (Fig. 130, _c_) and the superficial radial nerve (_g_), to the wrist, sending off branches to the integument. At the wrist it turns onto the dorsum of the hand, passing in a gentle curve to the ulnar side and distad, and giving off a branch for the space between each pair of metacarpal bones. These branches (Fig. 130, _e_) (=Aa. digitales dorsales=) pass distad and anastomose with branches coming from the palm.

_f._ =A. radialis= (Fig. 123).--Distad of the convexity of the elbow the brachial artery takes the name =radial artery=. It passes from the supracondyloid foramen on the medial side of the biceps tendon (1) and beneath the pronator teres muscle (5), giving off small branches, as far as the middle of the forearm, where it gives off the ulnar artery (_k_). It then passes from beneath the pronator teres (5) and lies on the surface of the fifth part of the flexor profundus (8), covered only by the fascia and integument. Near the wrist it sends off a branch (_m_) toward the ulnar side of the arm, which passes into the palm on the surface of the tendon of the flexor profundus, giving twigs to the digits and to the pad in the palm. A branch from this may join the ulnar, and the common trunk thus formed passes into the hand and gives origin to the branches described under the ulnar artery. The presence and size of this branch of the radial varies with the size of the ulnar artery, it being smaller or absent as the ulnar is larger. It is shown at _m_, Fig. 123. The radial artery (_g_) now turns gradually dorsad and passes beneath the tendon of the extensor brevis pollicis onto the dorsum of the hand. It passes over the oblique groove on the dorsal surface of the base of the second metacarpal beneath the tendon of the extensor carpi radialis longus and passes between the bases of the second and third metacarpals into the palm of the hand. Here it passes to the ulnar side and anastomoses with the ulnar artery to form the palmar arch.

=Branches of the Radial Artery.=

1. =A. radialis recurrens= (_i_).--The radial recurrent arises in the concavity of the elbow and sends a branch proximad to the structures in the concavity; it then continues to the radial side of the forearm at the elbow, supplying adjacent parts of the brachialis (2), the extensor carpi radialis, and the extensor communis digitorum.

2. =A. ulnaris recurrens= (_j_).--The ulnar recurrent arises on the medial side of the tendon of the biceps and supplies structures in the concavity of the elbow on the ulnar side, also the pronator teres (5) and proximal ends of the flexor carpi radialis and flexor profundis digitorum.

3. =Rami musculares.=--Muscular branches are given off along the course of the artery, to adjacent muscles. A nutrient artery to the radius leaves the radial artery about two centimeters distad of the supracondyloid foramen.

4. =Aa interosseæ= (=anterior= (_l_) and =posterior=) are given off usually separately between the origin of the ulnar artery and the biceps tendon. Sometimes they arise as a common trunk which soon divides. The =posterior interosseous artery= passes distad, supplying the flexor muscles of the forearm. It also sends a branch to the pronator teres. The =anterior interosseous= (_l_) may arise from the ulnar artery. It passes dorsad to the interosseous membrane, on which it runs distad; sends a nutrient branch to the ulna, and then passes to the wrist in the substance of the pronator quadratus, which it supplies. It sends a branch to the dorsal surface of the wrist; this ramifies on the carpus, forming a network of small arteries.

[Illustration: FIG. 123.--NERVES AND ARTERIES OF THE FOREARM, SEEN FROM THE FLEXOR SIDE.

Mm. palmaris longus, flexor carpi radialis, flexor carpi ulnaris, and the third and fourth heads of flexor profundus digitorum have been removed; also part of M. pronator teres. 1, biceps; 2, conjoined tendon of brachialis and clavobrachialis; 3, short portion of caput mediale of triceps brachii; 4, intermediate portion of caput mediale of triceps brachii; 5, cut ends of pronator teres; 6, brachioradialis; 7, extensor carpi radialis longus and brevis; 8, fifth head of flexor profundus digitorum; 9, second head of flexor profundus digitorum; 10, radial part of flexor sublimis digitorum; 11, common tendon of flexor profundus digitorum; 12, first head of flexor profundus digitorum; 13, cut origin of flexor carpi ulnaris. _a_, ulnar nerve; _b_, median nerve; _c_, dorsal cutaneous branch of the ulnar nerve; _d_, palmar branch of ulnar nerve; _e_, deep palmar branch; _f_, superficial palmar branch; _g′_, A. brachialis; _g_, A. radialis; _h_, A. collateralis ulnaris superior; _i_, A. radialis recurrens; _j_, A. ulnaris recurrens; _k_, A. ulnaris; _l_, A. interossea anterior; _m_, large branch of A. radialis, joining A. ulnaris.]

5. =A. ulnaris= (_k_).--The ulnar artery passes beneath the second, third, and fourth parts of the flexor profundus digitorum (but outside of the origin of the fifth part), to the inner surface of the flexor carpi ulnaris. It supplies the flexor carpi ulnaris, the flexor profundus and palmaris longus, and passes on the inner surface of the flexor carpi ulnaris to the wrist. Near the wrist it sends a branch onto the side of the forearm, and another to its midventral part, and ends in a small branch to the wrist on the radial side of the pisiform bone. This branch anastomoses with the radial to form the palmar arch, described below.

6. The =palmar arch= (Fig. 124) is formed by the termination of the radial artery (_a_) in the palm and its junction with the end of the ulnar (_f_). The radial artery reaches the palm between the bases of the second and third metacarpals and passes thence toward the ulnar side and distad, piercing the interosseus muscle of the third digit and lying on the outer surface of the interossei of the third and fourth digits beneath the adductors of the second and fifth digits. A small communicating branch from the radial passes to it between the first and second metacarpals.

Branches of the palmar arch:

=A. princeps pollicis et indicis= (_c_) leaves the palmar arch near its radial end and sends a branch onto the ulnar side of the thumb and one onto the radial side of the index.

The =palmar interosseæ= (_d_) are three in number. They leave the palmar arch (_b_) and pass distad and dorsad in the intervals between the four ulnar digits. The radial one passes along the ulnar side of the first digit, the ulnar one along the radial side of the fifth digit. The middle one divides and supplies the contiguous sides of the third and fourth digits. Each of these interosseous arteries sends off muscular branches (_e_) to the short muscles in the palm, and branches into the fibrous pad which occupies the palm of the hand. The palmar arch also sends branches onto the dorsum of the hand at the sides of the fourth metacarpal. Branches pass from these proximad to the wrist.

B. AORTA ABDOMINALIS. THE ABDOMINAL AORTA.--The abdominal aorta emerges into the abdomen from between the crura of the diaphragm, at about the level of the second lumbar vertebra. It passes caudad along the dorsal middle line, lying to the left of the inferior vena cava. It gives off =parietal= branches to the body wall, and =visceral= branches to the viscera, and ventrad of the first sacral vertebra it gives off two large branches on each side, the =external iliac= (Fig. 126, _k_) and the =hypogastric= (Fig. 126, _l_)--a very small median vessel, the =sacralis media= (Fig. 126, _o_), continuing the course of the aorta and passing into the tail.

The aorta gives off the following branches: =A. cœliaca=; =A. mesenterica superior=; =Aa. adrenolumbales=; =Aa. renales=; A. =mesenterica inferior=; =Aa. iliolumbales=; =Aa. lumbales= (seven pairs); =Aa. iliacæ externæ=; =Aa. hypogastricæ=.

A. =A. cœliaca= (Fig. 125).--The cœliac artery is a large branch which is given off from the aorta one centimeter or less caudad of the opening in the diaphragm. It passes directly ventrad about three or four centimeters, then divides, usually at once, into three branches. The most cranial of these is the =hepatic= (_d_), the next is the =gastrica sinistra= (_e_), while the third and largest, seeming to form a continuation of the cœliac, is the =splenic= (_f_) (=A. lienalis=). The cœliac artery may give rise also, before its division, to the two =phrenic= arteries (which, however, usually arise from the adrenolumbales), and either before or at the point of division to one or two small =Aa. ventriculi dorsales=, which, however, frequently arise from the gastrica sinistra.

[Illustration: FIG. 124.

THE PALMAR ARCH AND ITS BRANCHES IN THE PALM OF THE HAND.

The interosseous muscles have been removed, except those of the third and fourth digits. 1, M. abductor digiti quinti; 2, 3, Mm. interossei of third and fourth digits; 4, M. adductor pollicis; 5, M. flexor brevis pollicis. _a_, termination of radial artery; _b_, palmar arch; _c_, A. princeps pollicis et indicis; _d_, Aa. interosseæ; _e_, muscular branches of the same; _f_, A. ulnaris; _g_, deep palmar branch of ulnar nerve.]

Branches of the cœliac artery:

1. =A. hepatica= (_d_).--The hepatic artery passes cranioventrad, pierces the descending limb of the great omentum and passes craniad to the liver, lying, together with the portal vein and common bile-duct, in the ventral boundary of the foramen epiploicum (foramen of Winslow) and contained, together with the last-named vessels, in a fibrous sheath called the capsule of Glisson. Just before entering the sheath it gives off the =gastroduodenalis= (_g_). At its termination the hepatic artery divides, sending branches to the lobes of the liver and a =cystic= artery to the gall-bladder.

[Illustration: FIG. 125.--THE CŒLIAC ARTERY AND ITS BRANCHES.

_a_, abdominal aorta; _b_, A. cœliaca; _c_, A. mesenterica superior (cut); _d_, A. hepatica (cut); _e_, A. gastrica sinistra; _f_, A. lienalis; _g_, A. gastroduodenalis (cut from A. hepatica); _h_, A. pylorica; _i_, A. gastroepiploica dextra; _j_, A. pancreaticoduodenalis superior; _k_, A. pancreaticoduodenalis inferior (cut from inferior mesenteric); _l_, A. ventriculi dorsalis. 1, spleen; 2, stomach; 3, duodenum; 4, pancreas.]

_a._ =A. gastroduodenalis= (_g_).--This arises from the hepatic near the pylorus and passes caudad, dividing one or two centimeters from its origin into three branches, =A. pylorica= (_h_), =A. pancreaticoduodenalis superior= (_j_), and =A. gastroepiploica dextra= (_i_). The =pylorica= (_h_) (which may arise directly from the hepatic) passes to the pylorus, thence along the lesser curvature of the stomach, dividing into numerous branches and anastomosing with the gastrica sinistra. The =pancreaticoduodenalis superior= (_j_) passes to the duodenum, supplying it and the duodenal part of the pancreas and anastomosing with the pancreaticoduodenalis inferior (_k_). The =gastroepiploica dextra= (_i_) passes along the greater curvature of the stomach from the pyloric end and supplies the walls of the stomach, sending branches also to the ascending limb of the great omentum. These branches anastomose with the terminal branches of the splenic artery.

2. =A. gastrica sinistra= (_e_).--This arises from the cœliac artery and passes to the lesser curvature of the stomach, extending along this to the right. It gives off many branches to the walls of the stomach, and anastomoses with A. pylorica.

=A. ventriculi dorsalis= (_l_).--One or two small arteries which arise either from the gastrica sinistra or the cœliac artery, and pass toward the dorsal part of the greater curvature of the stomach near its cardiac end.

3. =A. lienalis= (_f_).--The splenic artery is the largest of the branches of the cœliac axis, of which it appears to be the direct continuation. It divides into two large branches, one to the cranial end, the other to the caudal end, of the spleen (1). From the latter a large branch passes to the pancreas and descending limb of the great omentum.

B. =A. mesenterica superior= (Fig. 126, _d_).--The superior mesenteric artery is larger than the cœliac. It supplies the blood to the small intestines and caudal portion of the pancreas and to the ascending and transverse colon. It arises from the ventral side of the abdominal aorta about one centimeter caudad of the cœliac axis and passes caudoventrad, forming a curve with the convexity dextrad. It gives off the =pancreaticoduodenalis inferior=, =colica media=, =colica dextra=, =ileocolica=, and numerous branches to the small intestine.

1. =A. pancreaticoduodenalis inferior= (Fig. 125, _k_).--This passes to the caudal end of the pancreas and a part of the duodenum, anastomosing with the pancreaticoduodenalis superior.

2. =A. colica media= is a large branch to the transverse and descending portions of the large intestine. It divides and sends branches in both directions which anastomose with the colica dextra and with branches from the inferior mesenteric arteries.

3. =A. colica dextra.=--A small branch which passes to the ascending and transverse colon, anastomosing with the colica media and ileocolica. It is sometimes absent.

4. =A. ileocolica.=--This passes to the cæcum and supplies that structure, sending branches to the ileocolic valve and the caudal end of the ileum, and anastomosing with the colica dextra and the intestinal branches of the superior mesenteric.

5. The superior mesenteric now divides into about sixteen terminal branches which pass to the small intestine. In many cases these branches unite near the intestine, forming arches, and from these arches numerous short branches pass to the intestine.

3. =A. adrenolumbalis= (or =lumboabdominalis=) (Fig. 126, _e_).--This rises from the aorta, one on each side, about two centimeters caudad of the superior mesenteric. Each passes laterad onto the dorsal body wall, supplying the muscles of this region. A large branch passes caudad along the surface of the muscles dorsad of the kidney and anastomoses with the iliolumbar artery. From the adrenolumbalis rises usually:

=A. phrenica= (_f_).--The phrenic artery rises either from the cœliac (_c_) or the adrenolumbalis (_e_) and passes to the diaphragm, near its dorsal border. In the diaphragm it passes ventrad, lying at the medial margin of the costal portion of the diaphragm, as far as its sternal portion, where it unites with the artery of the opposite side. The two thus form an arch, from which radiating arteries pass off to supply the diaphragm.

4. =A. renalis= (_g_).--The two renal arteries arise from the sides of the aorta, usually at about the same point, so that the left passes caudolaterad and the right craniolaterad (owing to the position of the kidneys). The artery usually divides just before entering the kidney (2). It passes dorsad of the vein (_t_). The renal artery sometimes sends a branch to the suprarenal body (1). It also occasionally gives origin to the spermatic artery (_h_).

[Illustration: FIG. 126.--ABDOMINAL BLOOD-VESSELS, VENTRAL VIEW.

_a_, vena cava inferior; _b_, abdominal aorta; _c_, A. cœliaca (cut); _d_, A. mesenterica superior (cut); _e_, A. adrenolumbalis; _f_, A. phrenica; _g_, A. renalis; _h_, A. spermatica interna; _i_, A. mesenterica inferior (cut); _j_, A. iliolumbalis; _k_, A. iliaca externa; _l_, A. hypogastrica; _m_, beginning of A. femoralis; _n_, A. umbilicalis; _o_, A. and V. sacralis media (_o_, the artery; _o′_, the vein); _p_, A. glutea superior; _q_, A. glutea inferior; _r_, A. and V. hemorrhoidalis media; _s_, V. adrenolumbalis; _t_, V. renalis; _u_, V. spermatica interna; _v_, V. iliolumbalis; _w_, V. iliaca communis; _x_, V. femoralis; _y_, V. and A. profunda femoris; _z_, V. hypogastrica. 1, suprarenal body; 2, kidney; 3, ureter; 4, outline (broken) of rectum.]

5. =A. spermatica interna= (_h_).--This rises from the aorta on each side at about the level of the caudal ends of the kidneys, and passes laterad (or it may arise from the renal). In male specimens the artery turns caudad, along with the corresponding vein (_u_), and passes to the inguinal canal. Thence it passes along with the vas deferens and the vein (forming all together the spermatic cord) to the testes and the other structures in the scrotum.

In females (Fig. 112, 2, page 265) the artery is larger and passes more nearly directly laterad, being much convoluted. It passes to the ovary, being now called the =ovarian artery=. It sends branches into the ovary (_c_) and to the cranial end of the uterus (_f_); the latter anastomosing with branches of the uterine artery (3).

6. =A. mesenterica inferior= (Fig. 126, _i_).--The inferior mesenteric artery has its origin from the aorta at about the level of the last lumbar vertebra. It passes toward the large intestine, and near it divides into two branches, the =colica sinistra=, which passes craniad along the descending colon, anastomosing with the colica media, and the =superior hemorrhoidal=, which passes caudad along the descending colon and rectum and anastomoses with the middle hemorrhoidal (page 308).

7. =A. iliolumbalis= (Fig. 126, _j_).--The iliolumbar arteries arise from the aorta about two centimeters caudad of the inferior mesenteric and pass laterad over the ventral surface of the psoas minor and iliopsoas muscles. Each divides into two main branches, one passing caudad and the other craniad; these supply the muscles of this region. The cranial branch anastomoses with branches of the adrenolumbalis (_e_). The caudal branch sends an artery through the abdominal wall to appear at the cranial edge of the thigh; it passes onto the lateral surface of M. sartorius and extends here some distance distad.

8. =A. lumbalis.=--There are usually seven pairs of lumbar arteries, passing almost directly dorsad from the dorsal surface of the aorta; the first pair arising just craniad of the diaphragm, the last at the same level as the origin of the external iliac. The two arteries of a pair usually arise from the aorta one behind the other, or they may arise by a common trunk. They correspond to the intercostal arteries. They pass between the centra of the vertebræ and the muscles of the dorsal region, and send one main branch laterad, the other dorsad; both supply the dorsal muscles. From the dorsal branch small arteries pass into the vertebral canal to join the anterior spinal artery.

9. =A. iliaca externa= (Fig. 126, _k_).--The external iliac artery passes obliquely caudad from the aorta, lying ventrad of the common iliac vein and against the medial surface of the psoas minor muscle. It passes onto the ventral surface of this and the iliopsoas and at the same time reaches the tendon of the abdominal muscles; through a small opening in this tendon lying ventrocaudad of that for the iliopsoas, it leaves the abdominal cavity. On its emergence from the abdominal cavity onto the medial surface of the thigh it receives the name =A. femoralis= (_m_). The branches of the external iliac artery are described below (page 309).

10. =A. hypogastrica= (or iliaca interna) (Fig. 126, _l_).--The hypogastric or internal iliac arteries are given off from the aorta usually within a centimeter caudad of the external iliac. Each passes caudolaterad, lying on the medial side of the common iliac vein, and divides into branches which supply the structures within the pelvis and the muscles about the pelvic wall. There is much variation in the origin and relations of the branches of this artery. The following seems to be a very common arrangement: A very short distance from the origin the =umbilical= artery (_n_) is given off. The hypogastric artery then extends two or three centimeters and gives off =A. glutea superior= (_p_), which passes at once to the pelvic wall. A little farther caudad the hypogastric divides into the =middle hemorrhoidal= (_r_), to the rectum, and the =glutea inferior= (_q_), which passes out of the pelvis.

Branches of the hypogastric artery: