668 THE VASCULAR SYSTEMS 



The suprarenal artery (a. suprarcnalis media) (Fig. 467), or capsular artery, 

 arises, one from each side of the aorta, opposite the superior mesenteric artery. 

 It is a small vessel which passes obliquely upward and outward, over the corre- 

 sponding cms of the Diaphragm, to the under surface of the suprarenal gland, 

 to which it is distributed, anastomosing with capsular branches from the phrenic 

 and renal arteries. In the adult these arteries are of small size; in the fetus they 

 are as. large as the renal arteries. 



The renal arteries (aa. renales) (Fig. 467) are two large trunks which arise 

 from the sides of the aorta immediately below the superior mesenteric artery. 

 Each is directed outward across the corresponding crus of the Diaphragm, so as 

 to form nearly a right angle with the aorta. The right is longer than the left, on 

 account of the position of the aorta; it passes behind the inferior vena cava. The 

 left is somewhat higher than the right. Before reaching the hilum of the kidney, 

 each artery usually divides into four branches. Two of these vessels enter the 

 anterior portion and two the posterior portion of the kidney. There may be but 

 one renal artery; there may be two, three, four, or five branches. The greater 

 number of the branches generally lie between the renal vein and ureter, the vein 

 being in front of the arteries, the ureter behind. The anterior branches supply 

 three-fourths of the kidney, the posterior supply one-fourth. Each vessel gives off 

 a small branch to the suprarenal gland (a. suprarenal is inferior) and branches to 

 the ureter, ureteral branches, and to the surrounding cellular tissue and muscles, 

 perirenal branches. Hyrtl, in 1870, pointed out that the renal artery gives off a 

 branch which divides and supplies the dorsal or posterior portion of the kidney 

 and ureteral pelvis, and a branch which divides and supplies the ventral or 

 anterior portion of the kidney and the pelvis. The two circulations are distinct 

 and do not anastomose even at the periphery. Between these two sets of vessels 

 is a nearly bloodless zone, the exsanguinated renal zone of Hyrtl, which does not 

 correspond to the lateral border, but is one-half inch dorsal to the lateral longi- 

 tudinal renal border. The ventral or anterior segment is much the larger. In 

 very rare instances the bloodless zone corresponds to the lateral border (Kiimmel). 

 An incision of the middle third of the kidney exactly at the junction of the two 

 segments does not divide large vessels. As the incision approaches either pole 

 there is danger of cutting a large branch (Schede). Frequently there is a second 

 renal artery, which is given off from the abdominal aorta either above or below 

 the renal artery proper, the former being the more common position. Instead of 

 entering the kidney at the hilum, an accessory renal artery often pierces the 

 upper or the lower part of the gland. 



The spermatic arteries (aa. spermaticae internae) (Fig. 467) are distributed 

 to the testes. They are two slender vessels of considerable length, which arise 

 from the front of the aorta a little below the renal arteries. Each artery passes 

 obliquely outward and downward behind the peritoneum, resting on the Psoas 

 muscle, the right spermatic lying in front of the inferior vena cava, the left behind 

 the sigmoid flexure of the colon. It then crosses obliquely over the ureter (to 

 which it sends a few branches) and the lower part of the external iliac artery to 

 reach the internal abdominal ring, through which it passes, and accompanies 

 the other constituents of the spermatic cord along the inguinal canal to the scrotum, 

 where it becomes tortuous and divides into several branches. Two or three of 

 these accompany the vas deferens, anastomosing with the artery of the vas deferens, 

 and are distributed to the epididymis; others pierce the back part of the tunica 

 albuginea and supply the substance of the testis. The spermatic artery in the 

 inguinal canal gives off cremasteric branches to supply the Cremaster muscle. In 

 the canal and scrotum the artery lies behind the pampiniform plexus and in front 

 of the vas deferens. 



