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female ovarian arteries. In each sex they are long slender vessels which spring from the front of the aorta a short distance below the origins of the renal arteries.

3a. The Testicular Arteries.—Each testicular artery runs downwards and forwards, on the anterior surface of the psoas major, to the abdominal inguinal ring, where it comes into relation with the ductus deferens. It accompanies the ductus deferens through the inguinal canal to the testis, to which it is distributed.

Relations-Posterior.—The right artery passes in front of the inferior vena cava, and as each artery descends, on the anterior surface of the psoas major, it passes in front of the corresponding genito-femoral nerve and the ureter.

Anterior.—Each artery is in relation anteriorly with the peritoneum to which it is attached ; but crossing in front of the right artery and intervening between it and the peritoneum are the third or transverse part of the duodenum, the right colic and the ileo-colic arteries, the terminal part of the superior mesenteric artery, and the cæcum. Crossing anterior to the left artery are the left colic and sigmoid branches of the inferior mesenteric artery and the iliac colon.

In the lower part of the abdominal portion of its course each testicular artery is accompanied by two veins, which issue from the pampiniform plexus in the inguinal canal and enter the abdomen through the abdominal inguinal ring, but at a higher level the two veins usually fuse into a single stem.

As it enters the inguinal canal each testicular artery passes in front of the inferior epigastric artery, and the lower end of the external iliac artery; and as it runs downwards and medially, in the canal, it is accompanied by the ductus deferens, and is more or less enclosed in the meshes of the pampiniform venous plexus. At the lower end of the canal it passes through the subcutaneous inguinal ring and descends in the scrotum, lying antero-lateral to the ductus deferens and in close association with the anterior group of testicular veins. At the upper end of the testis it breaks up into branches, some of which are distributed to the testis and others to the epididymis.

Branches.—In the abdominal part of its course each testicular artery gives off :-
(a) Ureteral branches, to the abdominal part of the ureter.
6 Peri-nephric twigs, to the peri-nephric fat.

Peritoneal branches, which are distributed to the peritoneum.

Glandular branches, which supply blood to the lumbar lymph glands.
Its terminal branches are the testicular and epididymal twigs already mentioned.

35. Ovarian Arteries. -The course and the relations of each ovarian artery, as far as the level of the brim of the pelvis minor, are the same as the relations of the corresponding testicular artery; but at the level of the upper end of the external iliac artery each ovarian artery turns medially, crosses anterior to the upper end of the corresponding external iliac artery and vein, and enters the upper part of the broad ligament of the uterus. In the broad ligament it runs medially, below the uterine tube, to the level of the ovary. There it turns backwards and passes between the layers of the mesovarium, where it breaks up into terminal branches which enter the ovary through the hilum in its anterior border. As it lies in the broad ligament each ovarian artery is accompanied by the pampiniform plexus of ovarian veins. In the lower portion of the abdominal part of its course it is accompanied by two veins, which issue from the pampiniform plexus at the brim of the pelvis minor, and unite at a higher level into a single trunk.

Branches.-(a) In the abdominal part of its course the branches of the ovarian artery are the same as those of the testicular artery.

In the pelvic part of its course it gives off :-
(a) Tubal branches, to the walls of the uterine tube.
(6) Branches to the round ligament of the uterus.

Uterine branches, which pass towards the uterus to anastomose with the branches of the uterine artery.

THE UNPAIRED OR SINGLE VISCERAL BRANCHES OF THE ABDOMINAL AORTA.

1. Arteria Coeliaca.—The cæliac artery (Figs. 771 and 773) arises from the front of the abdominal aorta, immediately below the aortic orifice of the diaphragm and between its crura. It is a short but wide vessel which runs almost horizontally forwards, for a distance of about 12 mm. (half an inch), and it terminates by dividing into three branches—the left gastric, the hepatic, and the splenic.

Relations. As the short trunk lies behind the omental bursa it runs forwards, below the caudate lobe of the liver and above the upper border of the pancreas and the splenic vein. It is surrounded by the cæliac plexus of the sympathetic, and has the right cæliac ganglion to its right side and the left coeliac ganglion to its left side.

Branches.-(a) The left gastric (O.T. coronary) is the smallest branch of the coeliac artery. It runs obliquely upwards and to the left, and reaches the lesser curvature of the stomach close to the cesophagus. It then turns sharply forwards, downwards, and to the right, and runs towards the pyloric end of the stomach to anastomose with the right gastric branch of the hepatic artery. In the first part of its course the artery lies posterior to the omental bursa ; it then passes into the left gastro-pancreatic fold, and is continued between the layers of the lesser omentum.

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Branches.(i.) Esophageal.- When the left gastric artery reaches the stomach it gives off an csophageal branch which passes upwards, on the oesophagus, and breaks up into branches which anastomose with @sophageal branches of the thoracic aorta and with branches of the inferior phrenic. (ii.) Gastric branches are distributed to both surfaces of the stomach. They anastomose with the short gastric branches of the splenic, and with branches of the gastroepiploic arterial arch on the greater curvature of the stomach.

(b) Arteria Lienalis.—The splenic artery (Fig. 771) is the largest branch of the celiac artery. It runs a tortuous course behind the stomach and the omental bursa, and along the upper border of the pancreas. It lies anterior to the left suprarenal gland and the upper end of the left kidney, and passes forwards between the two layers of the lieno-renal ligament, in which it divides into from five to eight terminal branches which enter the hilum of the spleen and supply the splenic substance. It is accompanied by the splenic vein, which lies below it.

Branches.—(i.) Pancreatic.—Numerous small branches are given off to the pancreas. A larger branch (pancreatica magna), occasionally present, enters the upper border of the pancreas, about the junction of its middle and left thirds, and runs from left to right in the substance of the pancreas, a little above and posterior to the pancreatic duct. Both the small and large arteries supply the substance of the pancreas, and anastomose with one another and with branches of the pancreaticoduodenal arteries. (ii.) The short gastric branches (O.T. vasa brevia), four or five in number, are given off

, either from the terminal part of the splenic artery or, more commonly, from some of its terminal branches. They pass between the layers of the gastro-splenic ligament to the left part of greater curvature of the stomach, and anastomose with the esophageal, the left gastric, and the left gastro-epiploic arteries.

(iii.) The left gastro-epiploic branch arises from the front of the splenic, close to its termination, and passes forwards, between the layers of the gastro-splenic ligament, to the left end of the lower part of the greater curvature of the stomach, along which it is continued, from left to right, between the layers of the greater omentum. It ends by anastomosing with the right gastro-epiploic artery, and it gives off numerous gastric branches to both surfaces of the stomach ; they anastomose with the short gastric and with branches of the left and right gastric arteries. Long slender omental branches pass to the omentum and anastomose with branches of the colic arteries.

(c) Arteria Hepatica.—The hepatic artery (Fig. 771) runs along the upper border of the head of the pancreas to the right gastro-pancreatic fold of peritoneum, in which it turns forwards to the upper border of the first part of the duodenum. It then passes upwards, between the layers of the hepato-duodenal ligament, anterior to the portal vein and to the left of the bile duct, and reaches the porta hepatis, where it divides into right and left branches.

Branches.-(i.) The right gastric artery is a small branch which arises opposite the upper border of the first part of the duodenum. It runs to the pylorus, between the layers of the lesser omentum, and then turns to the left along the smaller curvature of the stomach. It gives branches to both surfaces of the stomach, and terminates by anastomosing with the left gastric artery.

(ii.) The gastro-duodenal artery.—This branch of the hepatic arises just above the upper border of the first part of the duodenum, descends behind it and terminates opposite its lower border. In its course it lies between the neck of the pancreas and the first part of the duodenum, and anterior to the portal vein. The bile duct is on its right side. The vessel ends by dividing into the right gastro-epiploic and the superior pancreatico-duodenal arteries. The right gastro-epiploic artery is the larger of the two terminal branches of the gastro-duodenal; it passes from right to left, along the greater curvature of the stomach, between the layers of the greater omentum, and unites with the left gastro-epiploic branch of the splenic artery. From the arterial arch so formed branches pass upwards on both surfaces of the stomach, to anastomose with branches of the right and left gastric arteries. Other branches pass downwards in the greater omentum, and anastomose with branches of the colic arteries. The superior pancreatico-duodenal artery runs a short course to the right, between the duodenum and the head of the pancreas, and divides into anterior and posterior terminal branches, which descend, the former in front of and the latter behind the head of the pancreas, to anastomose with similar branches of the inferior pancreatico-duodenal artery. They supply the head of the pancreas, anastomosing in it with the pancreatic branches of the splenic artery ; branches are given also to the second part of the duodenum and to the bile duct.

(iii.) Terminal branches. — The right hepatic artery passes, either in front of or behind the hepatic duct and behind the cystic duct, to the right end of the porta hepatis ; there it divides into two or more branches which enter the substance of the liver and accompany the branches of the portal vein and the hepatic duct. As it crosses above the junction of the hepatic and cystic ducts, the right hepatic artery gives off a cystic branch. The cystic artery runs downwards and anteriorly, along the cystic duct, to the gall-bladder, where it divides into anterior and posterior branches; the anterior passes downwards between the gall-bladder and the visceral surface of the liver, to both of which it gives offsets ; the posterior branch is distributed on the posterior surface of the gall-bladder, between it and the peritoneum. The left hepatic artery is longer and narrower than the right. It runs to the left end of the porta hepatis, gives one or two branches to the caudate lobe, crosses the fossa of the umbilical vein, and breaks up into branches which terminate in the substance of the left lobe of the liver.

2. Arteria Mesenterica Superior.-The superior mesenteric artery (Figs. 772 and 773) springs from the front of the aorta, about 12 mm. (half an inch) below the origin of the coeliac artery and opposite the first lumbar vertebra.

It passes obliquely downwards and forwards, crossing anterior to the left renal vein, the uncinate process of the head of the pancreas, and the third or transverse

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part of the duodenum; opposite the latter it enters the root of the mesentery, in which it continues to descend, curving obliquely from above downwards and to the right, to the right iliac fossa, and crossing, in this part of its course, obliquely in front of the aorta, the lower part of the inferior vena cava, the right ureter, and the right psoas major muscle. At its origin it lies posterior to the neck of the pancreas and the splenic vein; where it passes in front of the duodenum it is crossed

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Fig. 772.—THE SUPERIOR MESENTERIC ARTERY AND ITS BRANCHES.
Note the difference in the number and arrangement of the loops formed by the

jejunal branches as contrasted with the ileal branches.

anteriorly by the transverse colon; and in the lower part of its extent it is behind the coils of small intestine.

Branches. It gives off numerous branches which supply the duodenum and the pancreas in part, the whole of the small intestine below the duodenum, and the large intestine nearly as far as the left colic flexure.

The branches are as follows:
(a) The intestinal branches to the small intestine, varying from ten to sixteen in

number, are separable into two groups, jejunal and ileal; they spring from the convexity of the superior mesenteric artery, and pass obliquely forwards and downwards, between the layers of the mesentery, each dividing into two branches which anastomose with adjacent branches to form a series of arcades, from which secondary branches are given off. This process of division and union is repeated three or four times in the case of the ileal arteries; thus four or five tiers of arches are formed, from the most distal of which terminal branches are given off to the walls of the jejunum and ileum. Branches from the successive arcades are also given off to the mesenteric lymph glands. The terminal branches anastomose together in the walls of the gut, forming a vascular network, which communicates above with the inferior pancreatico-duodenal artery and below with the terminal branch of the superior mesenteric trunk. The arterial loops and branches are accompanied by corresponding veins, lymphatics, and nerves.

(6) The inferior pancreatico-duodenal artery. This branch arises either from the trunk of the superior mesenteric, at the upper border of the third part of the duodenum, or from the first jejunal branch. It runs to the right, between the head of the pancreas and the third part of the duodenum, and terminates by dividing into two branches, anterior and posterior, which ascend, the former in front, and the latter behind the head of the pancreas; they supply the head of the pancreas, the descending and inferior parts of the duodenum, and they anastomose with the similar branches of the superior pancreatico-duodenal artery.

(c) The middle colic artery is a large branch which springs from the front of the superior mesenteric as it enters the root of the mesentery. It runs downwards and forwards, in the transverse mesocolon, and terminates by dividing into two branches, right and left, which anastomose respectively with the right and left colic arteries, forming arcades. Secondary and tertiary loops are sometimes formed and the terminal branches are distributed to the walls of the transverse colon.

(d) The right colic artery springs from the right or concave side of the superior mesenteric, either alone or in the form of a common trunk which divides into right colic and ileo-colic branches. It runs to the right, posterior to the peritoneum on the posterior wall of the abdomen, and in front of the right psoas major, the ureter, and the internal spermatic vessels, towards the ascending colon, near which it divides into an ascending and a descending branch. The former passes upwards, and anastomoses, in the transverse mesocolon, with the middle colic artery. The latter descends to anastomose with the upper branch of the ileo-colic, and from the loops thus formed branches are distributed to the walls of the ascending colon and the beginning of the transverse colon.

(e) The ileo-colic artery arises by a common trunk with the right colic, or separately from the right side of the superior mesenteric, and passes downwards and to the right, behind the peritoneum, towards the lower part of the ascending colon, where it terminates by dividing into an ascending branch which anastomoses with the lower branch of the right colic, and a descending branch which communicates with the colic terminal branches of the superior mesenteric trunk.

(1) Terminal. — The lower end of the superior mesenteric artery divides into five branches—(i.) ileal, (ii.) appendicular, (iii.) anterior ileo-cæcal, (iv.) posterior ileo-cæcal, and (v.) colic.

The ileal branch turns upwards and to the left in the lowest part of the mesentery, and anastomoses with the intestinal arteries. The appendicular branch passes behind the terminal portion of the ileum, and through the mesentery of the vermiform process to the vermiform process, upon which it ends. The anterior ileo-cæcal crosses the front of the ileo-cæcal junction in a fold of peritoneum; the posterior ileo-cæcal crosses the ileo-cæcal junction posteriorly, and the colic runs upwards to the ascending colon. The ileo-cæcal branches supply the walls of the cæcum, and, like the colic branch, anastomose with branches of the ileo-colic artery. In some cases the majority or all of the above terminal branches spring from the ileo-colic.

3. Arteria Mesenterica Inferior. — The inferior mesenteric artery (Fig. 773) arises from the front of the aorta towards the left side, 37 mm. above the bifurcation; it passes downwards and slightly to the left, lying posterior to the peritoneum and anterior to the left psoas major muscle, to the upper and left border of the left common iliac artery, where it becomes the superior hæmorrhoidal.

Branches.(a) The left colic artery arises from the left side of the inferior mesenteric near its origin, and almost immediately divides into an upper and a lower branch. The upper branch runs upwards and to the left towards the left colic flexure, and to the lower pole of the left kidney, where it divides into (i.)a branch which enters the transverse mesocolon, and, turning medially, terminates by joining the left branch of the middle colic

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