The abdominal aorta begins at the aortic hiatus of the diaphragm, in front of the lower border of the body of the last thoracic vertebra, and, descending in front of the vertebral column, ends on the body of the fourth lumbar vertebra, typically a little to the left of the middle line, by dividing into the two common iliac arteries (Fig. 1). The shape of the abdominal aorta is slightly convex forward with the summit of the convexity corresponding to the third lumbar vertebra. Numerous branches give off from the abdominal aorta before it divides into the common iliac arteries. The common iliac arteries are about 5 cm in length and diverge from the termination of the aorta. They pass downward and laterally before dividing into the external iliac and hypogastric arteries opposite the intervertebral fi-brocartilage between the last lumbar vertebra and the sacrum. The external iliac artery supplies the lower extremity while the hypogastric artery supplies the walls and viscera of the pelvis, the buttock, the generative organs, and the medial side of the thigh. The hypogastric artery is about 4 cm in length and smaller than the external iliac artery. After arising at the bifurcation of the common iliac opposite the lumbosacral articulation, it passes downward to the upper margin of the greater sciatic foramen where it divides into two large trunks, an anterior and a posterior trunk.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.