' ^ liver (margin raised and pushed forward] 



gall bladder 



pancreas 



position of pyloris (no valve) 



stomach 



large intestine 



small intestine 



bladder 



bulb of corpus covernosus 



vein 

 accessory bladder 



retractor muscle of penis 



Figure 9-10. Ventral view of viscera of the turtle Pseudemys. 



the large intestine which is involved and the loop is not at- 

 tached to the stomach. 



The liver is bilobed, and the gall bladder is to the right 

 of the ventral midline. There is a ventral mesentery. The 

 pancreas lies between the limbs of the closed duodenal loop; 

 it is irregularly shaped and more evident above than below. 

 The spleen is a small round body in the dorsal mesentery of 

 the stomach near the dorsal body wall. 



Embryological development The development of the gut 

 of the bird, reptile, or mammal is much the same; that of 

 the bird is well known. The form of the gut and its liver and 

 pancreatic outgrowths can be observed in the several stages 

 of the chick's development which are commonly studied. 



Amphibians 



In Necturus the pharynx tapers posteriorly to a constricted 

 esophagus which opens almost immediately into the stomach 

 (Figure 9-11). The stomach extends straight back to the 

 pyloris or curves slightly to the right. The first part of the 



small intestine passes to the right and dorsally, and then 

 posteriorly; this is the duodenum. Just before the posterior 

 limb, the bile duct and pancreatic ducts enter the anterior 

 or ventral aspect of the gut. From here the intestine de- 

 scribes a number of short loops in a semicircle around an 

 area of dorsal mesentery in which the hepatic portal blood 

 vessels lie. The anterior end of the large intestine is without 

 a caecum and lies only a short distance behind the stomach. 

 The large intestine extends back to the cloaca. The cloaca 

 is a simple chamber into which the bladder opens ventrally; 

 the ureters, the vasa deferens (nephric ducts), and Miillerian 

 ducts enter dorsolaterally. Cloacal glands swell this region 

 of the male at the reproductive time. 



There is a ventral septum, the falciform ligament, below 

 the liver. This is continued posteriorly as a strand enclosing 

 the ventral abdominal vein. The liver lies below the gut 

 and is attached to it by a band of tissue enclosing the bile 

 duct, the hepatic portal vein, and the coeliacomesenteric 

 artery. A gastrohepatic ligament (septum) is restricted to the 

 anterior third of the liver. The dorsal mesentery is complete 

 except for a section above the loop formed by the posterior 

 end of the stomach and the first part of the intestine. 



262 



THE VISCERA 



