THE VASCULAR SYSTEM 157 



sixteen or more smaller branches supply the small intestine. 

 The renal arteries supply the kidneys and sometimes the adrenal 

 bodies. Occasionally the spermatic artery may arise from the 

 renal and in rare instances the phrenic artery has a similar 

 origin. The genital arteries are small, and arise from one to 

 two centimeters caudad of the renal arteries. They pass 

 obliquely caudad to the ovaries in the female, and more directly 

 caudad to the testes in the male. The ovarian arteries are 

 larger than the spermatic. The inferior mesenteric is almost 

 as large as the superior mesenteric. It is distributed to the 

 large intestine. Its two large branches are, the colica sinistra, 

 and the superior hemorrhoidal. The iliolumbar arteries are 

 small branches supplying the muscles of the iliac region. 

 Four of live pairs of lumbar arteries are given off from the 

 dorsal side of the aorta at regular intervals between the dia- 

 phragm and the origin of the external ihac arteries. They 

 supply the muscles of the back and spinal cord. The external 

 iliac arteries are the largest branches of the abdominal aorta 

 and carry blood to the hind-limbs. The internal iliac arteries 

 arise more than a centimeter caudad to the external iliacs and 

 furnish blood to the pelvic viscera and the muscles of the 

 innominate region. The caudal (sacraHs media) artery is the 

 continuation of the aorta beyond the origin of the internal 

 iliacs. It extends into the tail (Figs. 78 and 84). 



ARTERIES OF THE HEAD AND NECK 



From the arch of the aorta arise the innominate and left 

 subclavian, which supply the sternum, neck, head, and anterior 

 extremities with blood. The innominate gives off the left 

 carotid and then divided into the right carotid and right sub- 

 clavian (Fig. 79). Sometimes the two carotids arise as a single 

 trunk from the innominate, which is then continued as the right 

 subclavian. In this case the common trunk of the carotid 

 usually bifurcates within one or two centimeters of its origin. 



