The Renal Arteries are two in number, one on each side: they arise from the aorta opposite to about the second lumbar vertebra, inferior and close to the origin of the superior mesenteric: sometimes the left arises a little higher than the right. After their origin, each of them proceeds at nearly a right angle towards the corresponding kidney. The right renal artery is longer than the left, on account of having its origin on the left side of the spine; posteriorly it rests on the spine, right sympathetic nerve, and psoas muscle; anteriorly it is covered by the left renal vein, the inferior cava, and the right renal vein: thus it is nearly covered by these veins in its entire course, so that without disturbing these vessels a very small portion only of the artery can be seen. Its branches, four or five in number, penetrate the pelvis of the kidney' between the branches of the vein which are in front, and the ureter which is posterior and inferior. The left renal artery lies on a small portion of the psoas muscle covered by its corresponding vein: the branches, however, do not enter the kidney behind the veins, as they do usually on the right side, but frequently they are situated in front of the branches of the left renal vein: in the hilus of both kidneys the ureter lies posterior and inferior to the blood-vessels.

Fig. 39. The Abdominal Aorta and its deep Branches.

A, Abdominal Aorta between the Pillars of the Diaphragm. B, Cceliac Axis, dividing into the Gastric. Hepatic, and Splenic Arteries. C, Superior Mesenteric Artery, cut. D, D, Renal Arteries. E, E, Common Iliac Arteries. F, F, External Iliac Arteries. G, G, Internal Iliac Arteries, a, a, Inferior Phrenic Arteries, b, b, Superior Capsular Arteries, c, c, Middle Capsular Arteries, d, d, Spermatic Arteries, e, Inferior Mesenteric Artery, f, f, f, Lumbar Arteries of right side, g, Middle Sacral Artery, h, h, Internal Circumflexae Ilii Arteries, i, Epigastric Artery. K, Vas Deferens. 1, Internal Abdominal Ring. I, Xiphoid Cartilage or Appendix. 2. 3, 4, Diaphragm. 5, Opening for Inferior Cava. 6, (Esophageal Opening. 7, Union of the Pillars. 8, 9, Pillars of the Diaphragm. 10, 10, Supra-Renal Capsules. 11, 11, The Kidneys. 12, 12, Pelvis of the Kidney. 13, 13, Psoas Magnus Muscles. 14, 14, Quadratus Lumborum. 15, 15, Internal Iliac Muscle. 16, Promontory of the Sacrum. 17, Rectum. 18, Urinary Bladder. 19, Peritoneum. 20, Left Rectus Muscle. 21, Aponeurosis over left Transverse Muscle.