Part 68

1. =A. thoracica anterior= (Fig. 122, h).--The anterior thoracic is a slender artery which leaves the ventral side of the axillary opposite the first rib and passes caudomediad, to supply the medial ends of the pectoral muscles (g).

2. =A. thoracica longa= (p).--The long thoracic artery is larger than the preceding, leaves the axillary a short distance laterad of it, and passes caudad to the middle portions of the pectoral muscles (8) and continues to the inner surface of the latissimus dorsi.

A short distance beyond the long thoracic the axillary divides into two. The more cranial one of these is the =subscapular= (l); the other is the =brachial= (g′).

3. =A. subscapularis= (l).--The subscapular artery passes laterad and gives off a short distance from its origin the =A. thoracicodorsalis= (t) and =A. circumflexa humeri posterior= (see below); it may also give rise to the =circumflexa anterior humeri= (l′), and to the =profunda brachii= (u); these two branches, however, rise more frequently from the brachial artery (g′) and are described in connection with it. The subscapular artery then passes through the triangular interval between the scapular end of the long head of the triceps, the latissimus dorsi, and the glenoid border of the scapula. Within this interval it sends muscular branches to the long head of the triceps, the subscapularis, and the latissimus dorsi. That to the latter muscle is very large. At the border of the scapula, opposite the tuberosity of the spine, it turns craniad, passes over the lateral surface of the infraspinatus muscle, supplying it; crosses the spine, and sends branches into the supraspinatus fossa in both directions parallel to the scapular spine. These supply the supraspinatus, acromiotrapezius, and spinotrapezius, and anastomose with the branches of the transversa scapulæ. As the subscapularis turns craniad onto the surface of the infraspinatus it sends dorsad a small branch, the =circumflexa scapulæ=, which passes in the infraspinatus fossa close to its glenoid border as far as the glenovertebral angle, supplying the infraspinatus and latissimus dorsi by lateral branches.

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.

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.