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(5) The dorsal carpal branch of the ulnar artery arises from the ulnar side of the ulnar artery, immediately proximal to the pisiform bone. It passes dorsally, deep to the ulnar flexor and the ulnar extensor of the carpus, to the dorsum of the carpus, where it unites with the dorsal carpal branch of the radial to form the dorsal carpal arch. (6) Profunda.—This branch

Triceps passes distally between the abductor and flexor brevis

Brachio-radialis digiti quinti, and, turning towards the radial side, deep to the flexor brevis, the opponens digiti quinti, and the long flexor

Extensor carpi

radialis longus tendons and their sheaths, it Anconæus joins the termination of the

Extensor carpi radial artery to complete the deep volar (palmar) arch.

Extensor digitorum

communis

Supinator THE ARTERIAL ARCHES OF Interosseous

Extensor carpi THE WRIST AND HAND.

recurrent

radialis brevis artery

Dorsal Arcus Carpeus Volaris Dorsal inter

interosseous nerve - The Volar Carpal Arch (Figs.

osseous artery
Flexor carpi

Pronator teres 768 and 769).—The volar car

ulnaris pal arch lies on the volar aspect

Abductor pollicis of the volar carpal ligaments,

longus (O.T.

Extensor ossis deep to the long flexor

tendons
Extensor carpi

metacarpi pollicis) and their synovial sheaths. It is formed by the union of the

Extensor pollicis volar carpal branches of the

longus radial and ulnar arteries,

Extensor pollicis

brevis and it receives the communicating branch from the volar Volar inter

osseous artery interosseous artery and re

Extensor indicis

proprius current branches from the

Dorsal inter

osseous artery deep volar arch. The branches of distribution which pass from it supply the ligaments Dorsal carpal arch

Radial artery and synovial membrane of the radio-carpal and inter- Proximal per

Dorsales pollicis forating artery

arteries carpal joints.

Dorsal metaArcus Carpeus Dorsalis. carpal arteries -The Dorsal Carpal Arch. (Fig. 770). This arch lies on the dorsal carpal ligaments deep to the extensor tendons and their sheaths. It is formed by the union of the dorsal carpal branches

Dorsalis indicis

radialis of the radial and ulnar arteries, and receives the terminations of the volar and dorsal interosseous arteries.

FIG. 770.—THE DORSAL INTEROSSEOUS ARTERY AND THE SECOND Branches. (a) Articular

PART OF THE RADIAL ARTERY, WITH THEIR BRANCHES. to the adjacent articulations. (b) Dorsal metacarpal, two slender branches which run distally, along the third and fourth dorsal interosseous muscles, to the clefts of the fingers, where each divides into dorsal digital branches. They communicate near their origins with the deep volar arch by the proximal perforating arteries, and near their terminations with the volar digital vessels through the distal perforating arteries. Their digital terminal branches run distally, on the dorso-lateral aspects of the fingers which bound the third and fourth interosseous spaces, and they anastomose with the special volar digital branches of the volar digital arteries.

[graphic]

Arcus Volaris Superficialis. — The superficial volar arch (O.T. superficial palmar) (Fig. 768) includes the terminal portion of the ulnar artery, and is usually completed on the radial side by the superficial volar, or by the volaris indicis radialis or the princeps pollicis branches of the radial artery. It extends from the ball of the little finger to the ulnar border of the superficial head of the flexor pollicis brevis, and reaches distally to a line drawn across the palm at the level of the distal border of the fully abducted thumb. It is accompanied by venæ comites and it is covered by the integuments and the central portion of the palmar aponeurosis, and, on the ulnar side of the palm, by the palmaris brevis. It is in contact dorsally with the flexor brevis and opponens digiti quinti, and with the common digital branches of the ulnar and median nerves, as well as with the flexor tendons and the lumbrical muscles.

Branches. —Four volar common digital arteries arise from the convexity of the arch. The most ulnar of the four passes along the ulnar border of the little finger, accompanied by the common digital branch of the ulnar nerve; the other three pass distally superficial to the common digital nerves, one along the middle of each of the ulnar three interosseous spaces, towards the interdigital clefts, just proximal to which each common digital artery divides into two special digital arteries which supply the contiguous sides of the fingers bounding the cleft. As the special digital branches pass along the sides of the fingers they lie superficial to the corresponding special digital nerves, and supply branches to the joints, to the flexor tendons and their sheaths, and to the skin and subcutaneous tissues on the volar surfaces of the fingers ; they give off dorsal branches also which anastomose with the dorsal digital arteries and supply the tissues on the dorsal aspects of the second and terminal phalanges. Some of the dorsally directed branches form a plexus in the matrix of the nail. In the pulp of the finger-tips anastomosing twigs join to form arches from which numerous branches are given off to the skin and subcutaneous fat.

Each of the three most radial special digital arteries is joined, immediately proximal to its division, by a volar metacarpal artery from the deep volar arch and a distal perforating artery from a dorsal metacarpal artery. The most ulnar digital artery is joined by a branch which arises either from the most ulnar volar metacarpal artery or from the deep volar arch.

Arcus Volaris Profundus.—The deep volar arch (O.T. deep palmar) (Fig. 769) extends from the base of the metacarpal bone of the little finger to the proximal end of the first interosseous space, and is formed by the terminal part of the radial artery anastomosing with the profunda branch of the ulnar. It is from 12 to 18 mm. (half to three-quarters of an inch) proximal to the level of the superficial volar arch. It lies deeply in the palm, in contact with the proximal ends of the bodies of the metacarpal bones and on the origin of the interossei muscles, and deep to the long flexor tendons and their synovial sheaths.

Branches.—(a) The proximal perforating : three small arteries which pass dorsally, through the ulnar three interosseous spaces and between the origins of the dorsal interosseous muscles. They anastomose on the dorsum of the hand with the dorsal metacarpal arteries.

(6) Small irregular recurrent branches pass proximally and unite with the volar carpal arch.

(c) The articular to the adjacent articulations.

(d) The volar metacarpal arteries are three vessels which pass distally, on the interosseous muscles of the three ulnar interosseous spaces, deep to the flexor tendons. They terminate by anastomosing with the volar digital arteries just before the latter vessels divide into special volar digital branches.

(e) The communicating, a small irregular branch which passes ulnarwards between the flexor tendons and the short muscles of the little finger to anastomose with the ulnar volar digital artery.

BRANCHES OF THE DESCENDING THORACIC AORTA. The branches given off from the thoracic portion of the descending aorta are distributed chiefly to the walls of the thorax and to the thoracic viscera. They contribute also to the supply of the spinal medulla and its membranes, and to that of the vertebral column and of the upper part of the abdominal wall. The

branches, which are numerous and for the most part arranged in pairs, are as e follows: Bronchial.

Intercostal.
Esophageal.

Subcostal.
Visceral.

Parietal.
Pericardial.

Superior phrenic.
Mediastinal.

The vas aberrans.

VISCERAL BRANCHES OF THE DESCENDING THORACIC AORTA. 1. Arteriæ Bronchiales.—The bronchial branches of the thoracic aorta are usually two in number

an upper and a lower—and both pass to the left lung. The upper left bronchial artery arises from the front of the aorta opposite the fifth thoracic vertebra; the inferior left bronchial artery usually takes origin near the lower border of the left bronchus. Both vessels are directed downwards and laterally to the back of the bronchus which they accompany, and, dividing similarly they follow its ramifications in the lung. They not only supply the walls of the bronchial tubes and the substance of the lungs, but also give branches to the bronchial glands, the pulmonary vessels, the pericardium, and the wesophagus.

As a rule there is only one right bronchial artery. It arises either from the first right aortic intercostal artery or from the upper left bronchial artery. More rarely it springs directly from the aorta. In its course and distribution it corresponds to the bronchial arteries of the left side.

2. Arteriæ Esophageæ.—The esophageal branches are variable; usually four or five small branches spring from the front of the aorta and pass forwards to the cesophagus, in the walls of which they ramify, anastomosing above with branches of the left bronchial and inferior thyreoid arteries, and below with @sophageal branches of the left gastric and the phrenic arteries.

3. The pericardial branches are three or four small irregular vessels which are distributed on the surface of the pericardium.

4. Small mediastinal branches pass to the areolar tissue and glands in the posterior mediastinum, and to the posterior part of the diaphragm.

PARIETAL BRANCHES OF THE DESCENDING THORACIC AORTA.

1. Arteriæ Intercostales—The Intercostal Arteries.—There are nine pairs of aortic intercostal arteries which usually arise separately from the back of the aorta, but, not uncommonly, a pair may take origin by a common trunk. They are distributed to the lower nine intercostal spaces, to the vertebral column, to the contents of the vertebral canal, and to the muscles and skin of the back The first three on each side give branches to the mammary gland also. The arteries of opposite sides closely correspond, but, since the aorta, in the thoracic region, lies on the left of the vertebral column, the right intercostal arteries cross the front of the column, posterior to the esophagus, the thoracic duct, and the vena azygos, and are longer than the left arteries. In other respects the courses of all the aortic intercostal arteries are almost identical. As each artery runs postero-laterally, across the side of the vertebral column, to an intercostal space, it passes posterior to the pleura, and is crossed, opposite the head of a rib, by the sympathetic trunk. The lower arteries are crossed by the splanchnic nerves also, and those on the left side are crossed by the hemiazygos or accessory hemiazygos veins.

As each artery passes laterally, between the necks of two adjacent ribs, it gives off a posterior branch. Then it ascends to the upper border of the space to which it belongs, and, passing either behind or in front of the corresponding intercostal nerve, is continued along the space, in the costal groove. In the space, as far as the angle of the rib, it lies between the pleura and the posterior intercostal membrane, and, in that part of its course, it is embedded in the endothoracic fascia. Then it is continued forward between the internal and external intercostal muscles. In the costal groove the artery lies between the corresponding vein above and the intercostal nerve below, and it terminates anteriorly by anastomosing with an anterior intercostal branch of the internal mammary or of the musculo-phrenic artery. The lower two intercostal arteries, on each side, extend beyond their spaces into the abdominal wall, and anastomose with branches of the superior epigastric, subcostal, and lumbar arteries. The first right aortic intercostal artery frequently gives off the right bronchial artery.

Branches.—(a) The posterior branch passes backwards, accompanied by the posterior branch of a spinal nerve, medial to the anterior superior costo-transverse ligament, between the necks of the ribs which bound the space, and between the adjacent transverse processes, to the vertebral groove, where it divides into a medial and a lateral cutaneous terminal branch. The medial cutaneous branch passes backwards and medially, either over or through the multifidus, giving branches to the muscles between which it passes and to the vertebral column. The lateral branch runs laterally under cover of the longissimus dorsi to the interval between it and the iliocostalis dorsi. It terminates in the skin of the back, after giving branches to the adjacent muscles. Before it divides, each posterior branch gives off muscular branches, and a spinal branch which passes through the corresponding intervertebral foramen, and enters the vertebral canal, to the contents and walls of which it is distributed. The spinal branch divides into three branches-neural, post-central, and pre-laminar. The neural branch divides into two branches which run medially, on the roots of the spinal nerve; they pierce the dura mater and arachnoid, and divide into branches some of which pass to the membranes of the spinal medulla, whilst others are continued on to reinforce the posterior and anterior spinal arteries. The post-central branch divides into ascending and descending branches which, anastomosing with similar branches above and below, form a series of vertical arches on the backs of the bodies of the vertebræ. The arches of opposite sides are connected by short transverse anastomoses. The pre-laminar branch is small, and its ascending and descending branches are distributed in a similar though less regular manner on the posterior wall of the vertebral canal.

(6) A collateral branch arises near the angle of the rib. It descends and runs forward along the lower border of the intercostal space, to anastomose in front with an anterior intercostal branch of the internal mammary or musculo-phrenic artery. The collateral branches of the lower two intercostal arteries, on each side, are inconstant ; when present they are small, and terminate in the abdominal wall.

(c) Muscular branches to the adjacent muscles are given off both by the main trunk and its collateral branch.

(d) A lateral cutaneous offset accompanies the lateral cutaneous branch of the intercostal nerve.

In addition to the secondary branches above-named, the trunk of the first aortic intercostal, on each side, anastomoses with the superior intercostal, and may supply the whole or the greater part of the second intercostal space. The

upper three or four aortic intercostal arteries, on each side, give branches to the mammary gland which anastomose with branches of the lateral thoracic and internal mammary arteries. Longitudinal anastomoses between adjacent trunks and also between adjacent posterior branches of intercostal arteries sometimes exist near the necks of the ribs, or near the transverse processes. These longitudinal anastomoses are of considerable morphological interest.

2. The subcostal arteries are the last pair of parietal branches given off from the thoracic aorta. They are in series with the aortic intercostal arteries, but are situated below the last ribs. Each gives off a posterior branch which behaves in the same manner as the posterior branch of an ordinary aortic intercostal artery. The trunk runs along the lower border of the twelfth rib in company with the last thoracic nerve. It passes below the arcus lumbocostalis lateralis to the abdomen, and there crosses anterior to the quadratus lumborum, and posterior to the kidney and the adjacent part of the colon. It next pierces the aponeurosis of origin of the transversus abdominis

, and runs between the transversus and the internal oblique muscles, anastomosing with the lower intercostal arteries, with the lumbar arteries, and with branches of the superior epigastric artery.

3. Superior phrenic branches are given off from the lower part of the thoracic aorta. They are small vessels which ramify on the upper and posterior surfaces of the diaphragm, and anastomose with branches of the pericardiaco-phrenic and musculo-phrenic arteries.

4. The vas aberrans is a variable and inconstant branch of the thoracic aorta; it represents the dorsal roots of the fourth and sixth right aortic arches of the embryo. When present it arises from the front and right side of the upper part of the descending aorta near the upper left bronchial artery, and passes upwards and to the right behind the resophagus; it frequently anastomoses with the right superior intercostal artery, and it may be enlarged and form the first part of the right subclavian artery.

BRANCHES OF THE ABDOMINAL AORTA. The branches of the abdominal portion of the aorta are distributed almost entirely to the walls and contents of the abdominal cavity, but some supply small branches to the vertebral column, and to the contents of the vertebral canal, and others are prolonged into the pelvis minor. They are divisible into visceral and parietal groups, both of which include paired and single (unpaired) vessels.

Suprarenal
Paired. Renal.

Inferior phrenic.

Paired. Lumbar.
Visceral.
Spermatic or ovarian.

Parietal.
Cæliac axis.

Common iliac.
Single. Superior mesenteric.

Single. Middle sacral. Inferior mesenteric.

THE PAIRED VISCERAL BRANCHES OF THE ABDOMINAL AORTA. 1. Arteriæ Suprarenales (Fig. 773). There are three pairs of suprarenal arteries — the superior, middle, and inferior. Of these the middle only arise directly from the aorta ; the superior spring from the inferior phrenic, and the inferior from the renal arteries.

The middle suprarenal arteries are two small branches which arise, posterior to the pancreas, from the sides of the aorta, close to the origin of the superior mesenteric artery. They run, one on each side, laterally and upwards, upon the crura of the diaphragm just above the renal arteries, to the suprarenal glands, to which they are distributed. They anastomose with the superior and inferior suprarenal arteries.

2. Arteriæ Renales.—The renal arteries (Fig. 773) arise, one on each side, from the aorta, about 12 mm. (half an inch) below the origin of the superior mesenteric artery and opposite the second lumbar vertebra.

Both arteries are of large size, and the right is frequently slightly lower in position than the left. Each artery runs almost transversely to the hilum of the corresponding kidney. It passes anterior to the crus of the diaphragm and the upper part of the psoas muscle. The left artery lies posterior to the pancreas; the right vessel passes behind the inferior vena cava, the head of the pancreas, and the descending part of the duodenum. The renal vein usually lies below and anterior to the artery, but near the kidney the vein not infrequently occupies a posterior position.

On reaching the hilum of the kidney each artery divides into three branches, two of which pass anterior to the pelvis renalis, and between it and the renal vein, and the third posterior to the pelvis. In the renal sinus these primary branches break up into numerous secondary branches which enter the kidney substance between the pyramids.

Branches. The following branches are given off by each renal artery, in addition to the terminal branches :

(a) Inferior suprarenal, which passes upwards to the lower part of the suprarenal gland.

(6) Ureteral.--Small branches to the upper part of the ureter, which anastomose with branches of the internal spermatic or ovarian arteries.

(c) Peri-nephric.—Small branches to the fatty capsule of the kidney, which anastomose with the lumbar arteries.

(d) Glandular offsets, either from the main trunk or from some of its branches, pass to the lumbar lymph glands.

3. Arteriæ Spermatica Internæ.—The internal spermatic arteries are present in both sexes; in the male they are called the testicular arteries and in the

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