. Chordate morphology. Morphology (Animals); Chordata. appendix Figure 9-1. Three stages in the development of the digestive tract of a mammal as seen in ventral view. (After Patten, 1946) armadillos, while Hyrax has several caecal pouches along the large intestine, including a pair of lateral diverticula. A caecum is lacking in some mammals—hippopotamus, the shrew Talpa, some bats, and bears. The large intestine curves forward on the right side of the body, as the ascending colon; turns across to the opposite side anterior to the general mass of the small intestine as the transverse colon; an
. Chordate morphology. Morphology (Animals); Chordata. appendix Figure 9-1. Three stages in the development of the digestive tract of a mammal as seen in ventral view. (After Patten, 1946) armadillos, while Hyrax has several caecal pouches along the large intestine, including a pair of lateral diverticula. A caecum is lacking in some mammals—hippopotamus, the shrew Talpa, some bats, and bears. The large intestine curves forward on the right side of the body, as the ascending colon; turns across to the opposite side anterior to the general mass of the small intestine as the transverse colon; and extends posteriorly as the de- scending colon. From here it extends as the sigmoid colon (man) to the midline rectum, which reaches to the anus. Either the small intestine (cat, rat, man) or the large intes- tine (pig) can be quite lengthened and spirally coiled. In some bats and a few primates (Pin-Tailed Tree Shrew—Fig- ure 9-2), the colon is short and straight. The monotremes agree with this general picture (Figure 9-3). The liver has several lobules that belong to the basic right and left lobes. The gall bladder lies to the right of the ventral midline. In Ormlhorhynchiis the stomach is sac-like and has no gastric glands. Its lining is like that of the esoph- agus (Figure 9-5). The pyloric opening is to the right of the esophageal entrance and there is no pyloric valve. The spleen is very large, extending from the mesentery above the stomach posteroventrally and medially through bifur- cate lobes to the posterior end of the body cavity. There is a frilled greater omentum extending back from the stomach between the coils of the gut and the spleen. The first part of the duodenum, perhaps the pyloric sec- tion of the stomach, is thick-walled, with a horny papillate lining and Brunner's glands in the submucosa. Since Brun- esophagus bile duct pleen. stomach Figure 9-2. Ventral view of the digestive tract of a Pen-tailed Tree Shrew, PWocercus. (After LeGros Clark, 1926) 25
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