The superior mesenteric artery gives off an inferior pancreatico-duodenal branch to the pancreas and duodenum; about twelve intestinal branches to the small intestines, which form in the substance of the mesentery a series of arches before they end in the wall of the intestines; an ileocolic branch to the end of the ileum, the caecum, and beginning of the colon; a right colic branch to the ascending colon; and a middle colic branch to the transverse colon.
The inferior mesenteric artery gives off a left colic branch to the descending colon, a sigmoid branch to the iliac and pelvic colon, and ends in the superior haemorrhoidal artery, which supplies the rectum. The arteries which supply the coats of the alimentary tube from the oesophagus to the rectum anastomose freely with each other in the wall of the tube, or in its mesenteric attachment, and the anastomoses are usually by the formation of arches or loops between adjacent branches.
The capsular arteries, small in size, run outward from the aorta to end in the supra-renal capsules.
The renal arteries pass one to each kidney, in which they for the most part end, but in the substance of the organ they give off small perforating branches, which pierce the capsule of the kidney, and are distributed in the surrounding fat. Additional renal arteries are fairly common.
The spermatic arteries are two long slender arteries, which descend, one in each spermatic cord, into the scrotum to supply the testicle. The corresponding ovarian arteries in the female do not leave the abdomen.
The branches of the aorta which supply the walls of the thorax, abdomen and pelvis, are the intercostal, the Parietal branches. lumbar, the phrenic, and the middle sacral.
| Fig. 1.—Diagram of a pair of intercostal arteries. |
| Ao, The aorta transversely divided, giving off at each side an intercostal artery. PB, The posterior or dorsal branch. AB, The anterior or proper intercostal branch. IM, A transverse section through the internal mammary artery. |
The intercostal arteries arise from the back of the thoracic aorta, and are usually nine pairs. They run round the sides of the vertebral bodies as far as the commencement of the intercostal spaces, where each divides into a dorsal and a proper intercostal branch; the dorsal branch passes to the back of the thorax to supply the deep muscles of the spine; the proper intercostal branch (AB.) runs outward in the intercostal space to supply its muscles, and the lower pairs of intercostals also give branches to the diaphragm and wall of the abdomen. Below the last rib a subcostal artery runs.
The lumbar arteries arise from the back of the abdominal aorta, and are usually four pairs. They run round the sides of the lumbar vertebrae, and divide into a dorsal branch which supplies the deep muscles of the back of the loins, and an abdominal branch which runs outward to supply the wall of the abdomen. The distribution of the lumbar and intercostal arteries exhibits a transversely segmented arrangement of the vascular system, like the transversely segmented arrangement of the bones, muscles and nerves met with in these localities, but more especially in the thoracic region.
The phrenic arteries, two in number, pass to supply the under surface of the diaphragm.