616 THE ARTERIES. 



The Renal Arteries. 



The renal arteries are two large trunks which arise from the sides of the 

 aorta immediately below the superior mesenteric artery. Each is directed 

 outward across the 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. Previously to entering the kidney each artery divides into four 

 or five branches which are distributed to its substance. At the hilum these 

 branches lie between the renal vein and ureter, the vein being usually in front, the 

 ureter behind. Each vessel gives off some small branches (inferior suprarenal} to 

 the suprarenal capsule, the ureter, and the surrounding cellular tissue and muscles. 

 Frequently there is a second renal artery, which is given off from the abdominal 

 aorta at a lower level and supplies the lower portion of the kidney. It is termed 

 the inferior renal artery. 



The Spermatic Arteries. 



The spermatic arteries are distributed to the testes in the male and to the 

 ovaria in the female. 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 

 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 Avhich accompany the vas 

 deferens and supply the epididymis, anastomosing with the artery of the vas 

 deferens ; others pierce the back part of the tunica albuginea, and supply the 

 substance of the testis. 



The Ovarian Arteries. 



The ovarian arteries are shorter than the spermatic, and do not pass out of 

 the abdominal cavity. The origin and course of the first part of the artery are the 

 same as the spermatic in the male, but on arriving at the margin of the pelvis the 

 ovarian artery passes inward, between the two laminae of the broad ligament of 

 the uterus, to be distributed to the ovary. One or two small branches supply the 

 Fallopian tube ; another passes on to the side of the uterus and anastomoses with 

 the uterine arteries. Other offsets are continued along the round ligament, 

 through the inguinal canal, to the integument of the labium and groin. 



At an early period of foetal life, when the testes or ovaries lie by the side of the 

 spine below the kidneys, the spermatic or ovarian arteries are short ; but as these 

 organs descend from the abdomen into the scrotum the arteries become gradually 

 lengthened. 



Parietal Branches of the Abdominal Aorta. 

 The Phrenic Arteries. 



The phrenic arteries are two small vessels which present much variety in 

 their origin. They may arise separately from the front of the aorta, immediately 

 above the cceliac axis, or by a common trunk, which may spring either from the 

 aorta or from the cceliac axis. Sometimes one is derived from the aorta, and the 

 other from one of the renal arteries. In only one out of thirty-six cases examined 

 did these arteries arise as two separate vessels from the aorta. They diverge from 

 one another across the crura of the Diaphragm, and then pass obliquely upward 

 and outward upon its under surface. The left phrenic passes behind the oesoph- 

 agus and runs forward on the left side of the cesophageal opening. The right 

 phrenic passes behind the inferior vena cava, and ascends along the right side of 

 the aperture for transmitting that vein. Near the back part of the central tendon 

 each vessel divides into two branches. The internal branch runs forward to the 

 front of the thorax, supplying the Diaphragm and anastomosing with its fellow of 



