Part 187

The =bronchial= and =œsophageal= arteries often arise separately.

Ten pairs of =intercostal arteries= usually arise from the aorta. The other three come from the subcostal artery.

The two =phrenic arteries= are very variable in origin. They may come from the aorta, the cœliac, left ruminal, or an intercostal or lumbar artery.

BRANCHES OF THE ABDOMINAL AORTA

The =cœliac artery= is about four to five inches (ca. 10 to 12 cm.) in length. It passes downward and curves forward between the rumen and pancreas on the left and the right crus of the diaphragm and the posterior vena cava on the right. It gives off five chief branches.

1. The =hepatic artery= arises from the convex side of the curve of the cœliac artery as it crosses the posterior vena cava. It passes downward, forward, and to the right above the portal vein to the portal fissure, and gives off the following branches:

(1) Pancreatic branches.

(2) Dorsal and ventral branches to the liver. The ventral branch is the larger; it gives off the right gastric artery, which runs in the lesser omentum to supply the origin of the duodenum and the pylorus, anastomosing with the dorsal branch of the omaso-abomasal artery.

(3) The cystic artery supplies the gall-bladder.

(4) The gastro-duodenal artery divides into right gastro-epiploic and pancreatico-duodenal branches. The right gastro-epiploic artery anastomoses with the left gastro-epiploic. The pancreatico-duodenal artery anastomoses with the first intestinal branch of the anterior mesenteric artery.

2. The =right ruminal artery= (A. ruminalis dextra) is the largest branch, and usually arises by a short common trunk with the splenic. It runs downward and backward on the right face of the dorsal sac of the rumen to the posterior transverse fissure, in which it turns around to the left and anastomoses with branches of the left ruminal artery. It gives off a pancreatic branch, dorsal and ventral coronary arteries, branches to the great omentum, and ramifies on both surfaces of the rumen.

3. The =left ruminal artery= (A. ruminalis sinistra) runs downward on the anterior part of the right face of the rumen, enters the anterior furrow, in which it runs from right to left, and continues backward in the left longitudinal groove, anastomosing with branches of the right artery. It supplies chiefly the left face of the rumen, but not its posterior part. It usually gives off near its origin the =reticular artery= (A. reticularis); this rather small vessel passes forward on the dorsal curvature of the rumen and turns downward in the rumino-reticular groove, in the bottom of which it runs around ventrally to the right side. It gives off a branch which passes to the left of the cardia and along the lesser curvature of the reticulum to the neck of the omasum. The reticular branches anastomose with the omaso-abomasal and left ruminal arteries.

4. The =omaso-abomasal artery= (A. gastrica sinistra) appears as the continuation of the cœliac. It passes forward and downward to the greater curvature of the omasum and divides after a course of four or five inches into two branches. The =dorsal branch= curves sharply backward on the dorsal surface of the omasum, continues along the lesser curvature of the abomasum, and anastomoses with the hepatic artery. It supplies branches to the omasum and to the lesser curvature and pyloric part of the abomasum. The =ventral branch= (A. gastroepiploica sinistra) runs forward and downward over the anterior extremity of the omasum, passes backward in the great omentum close to the ventral curvature of the abomasum, and anastomoses with the right gastro-epiploic. A considerable branch from it curves around in front of the neck of the omasum to communicate with the reticular artery. Another branch runs back across the left side of the omaso-abomasal junction, and a third goes to the lesser (ventral) curvature of the omasum.

5. The =splenic artery= usually arises by a common trunk with the right ruminal artery. It passes forward and to the left across the dorsal curvature of the rumen and enters the hilus of the spleen.

The =anterior mesenteric artery= arises from the aorta just behind the cœliac, and has about the same caliber as the latter. It passes downward and a little to the right, and crosses the colon as it emerges from the spiral to run backward. After detaching twigs to the pancreas it gives off in succession the following branches:

1. A branch (A. colica media) passes to the colon as it emerges from the spiral arrangement. This artery is comparable to the middle colic or artery of the small colon of the horse; it runs backward along the terminal part of the colon, which it supplies.

FIG. 472.—GASTRIC ARTERIES OF OX, RIGHT VIEW (PARTLY SCHEMATIC).

1, Cœliac artery; 2, right ruminal; 3, splenic; 4, reticular; 5, left ruminal; 6, omaso-abomasal; 7, dorsal branch of 6; 8, ventral branch of 6 (= left gastro-epiploic); A, dorsal sac of rumen; B, ventral sac of rumen; C, C, posterior blind sacs; D, œsophagus; E, reticulum; F, omasum; G, abomasum; H, duodenum; I, right longitudinal furrow of rumen. By an oversight the reticular artery is shown as arising from the omaso-abomasal. ]

FIG. 473.—GASTRIC ARTERIES OF OX, LEFT VIEW (PARTLY SCHEMATIC).

1, Left ruminal artery; 2, continuation of right ruminal artery; 3, reticular artery, which disappears into rumino-reticular groove; A, dorsal sac of rumen; B, ventral sac of rumen; C, C, posterior blind sacs; D, œsophagus; E, reticulum; F, rumino-reticular groove; G, left longitudinal furrow of rumen. ]

2. The ileo-cæco-colic artery ramifies on the right face of the spiral part of the colon. It gives off the ileo-cæcal artery, which divides into ileal and cæcal arteries.

3. An artery (Ramus collateralis) runs in the mesentery in a curve along the ventral border of the coils of the colon. (This vessel is absent in the sheep.)

4. An artery which constitutes the direct continuation of the anterior mesenteric pursues a course in the mesentery corresponding to the series of mesenteric lymph glands.

FIG. 474.—PLAN OF BRANCHES OF ANTERIOR MESENTERIC ARTERY OF OX.

1, Anterior mesenteric artery; 2, middle colic artery; 3, ileo-cæco-colic artery; 4, ramus collateralis; 5, continuation of anterior mesenteric artery, giving off branches to small intestine; 6, cæcal artery; 7, colic branch of posterior mesenteric artery; A, termination of duodenum. ]

The two preceding vessels are essentially the arteries of the small intestine, which they supply with the exception of its initial and terminal parts. The first gives off no considerable branches in its course along the ventral border of the coils of the colon, but on curving upward along the latter it anastomoses with the second artery and detaches numerous branches to the small intestine which form series of superposed anastomotic arches. It supplies, roughly speaking, about one-third of the small intestine and terminates by joining the ileal artery. The second artery gives off numerous branches which also form arches and supply about the first two-thirds of the small intestine, exclusive of the small part supplied by branches of the cœliac artery. Both arteries give branches to the lymph glands.

The =posterior mesenteric artery= arises from the aorta near its termination. It is small and supplies branches to the terminal part of the colon and to the rectum.

The =renal arteries= arise from the aorta close together. The right one passes outward and forward across the dorsal face of the posterior vena cava to the hilus of the kidney. The left one runs backward, but necessarily varies in direction in conformity with the position of the kidney (q. v.).