506 TEXTBOOK OF ZOOLOGY 



of the skull, giving off the palatine artery to the roof of the mouth, 

 the cerebral carotid which enters the skull and supplies the brain, 

 and the ophthalmic artery to the eye. 



The Systemic Arch. — The systemic arch soon after it leaves the 

 truncus supplies a small laryngeal artery to the larynx and mus- 

 cles of the hyoid. It then curves downward and around the esopha- 

 gus on each side. It gives off an occipitovertehral artery which 

 sends a small artery to the dorsal side of the esophagus, then branches 

 at the spinal cord into the occipital artery, running anteriorly on 

 the dorsal side of the skull to the orbit and tympanum, and the 

 vertebral artery, turning posteriorly along the spinal column. Imme- 

 diately posterior to the occipito vertebral artery the large subclavian 

 artery arises from the systemic arch. It branches to the shoulder and 

 adjacent body wall and enters the arm as the brachial artery. 



The systemic arches from each side, after curving under the ali- 

 mentary canal, meet near the anterior end of the kidneys and fuse 

 into a single large artery, the dorsal aorta, which extends posteriorly. 

 At or just posterior to this meeting point, there arises from the aorta 

 the large coeliacomesenteric artery which divides into an anterior 

 branch, the coeliac artery, and a posterior branch, the anterior mes- 

 enteric artery. The coeliac artery divides into right and left gastric 

 arteries. The latter runs directly to the dorsal or left side of the 

 stomach, while the former sends off small pancreatic arteries to the 

 pancreas ; a larger hepatic artery to the pancreas, gall bladder, and 

 liver; and continues to the ventral side of the stomach, where it is 

 distributed. The anterior mesenteric artery gives off the splenic 

 (lienal) artery to the spleen and then divides into two parallel ves- 

 sels which send numerous smaller arteries to the small and large 

 intestines. 



The urinogenital arteries consist of about four to six small much- 

 divided arteries which are given off from the ventral side of the dorsal 

 aorta to right and left, supplying the kidneys, reproductive organs, 

 and fat bodies. A few small lumbar arteries arise either as branches 

 of these or directly from the aorta and go to the body wall on each 

 side. The small posterior mesenteric artery is given off near the 

 posterior end of the aorta, passing to a portion of the rectum and, 

 in the female, to the ovisac. It often anastomoses on the rectum with 

 descending branches of the anterior mesenteric, 



