The aorta, after having passed the diaphragm is thus named. It rests on the bodies of the vertebras, extending from the front of the last dorsal to the fourth lumbar vertebra, a little to the left of the median line, where it usually divides. The anterior surface of the great artery is successively in apposition with the liver, the splenic vein, the pancreas, the third portion of the duodenum, the left renal vein, and the peritoneum. The vena cava lies at its right side, the right crus of the diaphragm being interposed at the upper part of the abdomen ; close to the same side, are the thoracic duct and the azygos vein, which are placed between the aorta and the right crus of the diaphragm. The aorta is surrounded by a mesh of nerves derived from the sympathetic.
The abdominal aorta, [aorta abdominalis, French : aorte abdominale], gives numerous branches, which may be divided into two sets, viz., those which supply the viscera and and those which are distributed to the walls of the abdomen. The former consist of the coeliac artery, the superior mesenteric , the inferieur mesenteric, the capsular, the renal, and the spermatic arteries ; which among the latter are included the phrenic, the lumbar, and the middle sacral arteries. The first three of the visceral branches are single arteries.
The pudic or internal pudic artery (pudica interna; pudica communis,— Winslow ; pudenda (simpliciter),— Haller), a branch of considerable size (smaller in the female than in the male), is distributed to the external generative organs. The following description of this artery has reference to its arrangement in the male;— its distribution in the female will be noticed separately.
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The anastomosis which exists between the obturator artery (when that vessel is derived from the internal iliac) and the epigastric, by means of those small branches of each which ramify behind the pubes, serves to afford some explanation of one of the most striking instances of variety of origin met with in the arterial system, viz., the transfer of the origin of the obturator from the internal iliac to the epigastric artery.
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The obturator artery [a.obturatoria], when derived from the internal iliac, usually arises from the anterior division of that vessel, but not infrequently from its posterior division. The artery is directed forwards through the pelvis to reach the groove on the under surface of the horizontal portion of the pubes, at the upper part of the thyroid foramen. Beneath this bone it passes out of the pelvis, and immediately divides into its terminal branches. In its course through the pelvis the artery is placed between the pelvic fascia and the peritoneum, a little below the obturator nerve. Beneath the pubes it lies with the nerve in an oblique canal, formed partly by the groove in the bone, and partly by fibrous tissue.
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