THE VASCULAR SYSTEM 101 



parallel to the horn of the uterus in the broad ligament. 

 Trace the uterine artery eaudally to its origin. 



The two iliolumbar arteries pass laterally in the lumbar 

 region from the dorsal aorta, along the dorsal surface of 

 the abdominal cavity, giving off branches to the muscles of 

 the back. Trace the terminal branches. 



The inferior mesenteric artery branches from near the 

 posterior end of the dorsal aorta, sends branches to the 

 rectum and descending colon, passes anteriorly along the 

 latter, and anastomoses with the superior mesenteric artery. 

 Is this anastomosis always present? 



The aorta bifurcates at its posterior extremity, forming 

 the right and left common iliac arteries. These give off 

 dorsal branches to the muscles of the back, then divide into 

 the external and internal iliac (hypogastric) arteries. The 

 latter, which runs dorsally, divides into two main branches, 

 one which passes laterally to the proximal region of the 

 thigh, while the other passes eaudally through the pelvic 

 region. Dissect out these branches. The external iliac 

 artery passes to the median surface of the thigh, there be- 

 coming the femoral artery. This gives off the saphenous 

 artery, then penetrating the thigh it courses distally to the 

 foot, supplying branches to the muscles of the thigh and 

 shank. Trace the saphenous along the median surface of 

 the shank, and note that its terminal branches enter the 

 foot. 



The middle sacral artery arises from the dorsal aorta 

 near its posterior end and proceeds eaudally through the 

 pelvic region into the tail. Trace it and observe its 

 branches. 



The unpaired lumbar arteries pass dorsally from the 

 abdominal section of the dorsal aorta. They correspond 

 to the intercostal arteries of the thoracic region. The 

 lumbar arteries bifurcate ventral to the vertebral column, 



