Alimentary Canal: Anatomy, Regulation of Feeding, and Motility

Abstract

As do other avian systems, the digestive system shows adaptations for flight (Farner, 1960). In the mouth area, the teeth and heavy jaw bones and muscles of reptiles and mammals have been replaced by a much lighter beak, jaw bones, and jaw muscles in birds. Since birds do not chew food, the esophagus is large in diameter to accommodate larger food items. The heavy muscular gizzard, or muscular stomach (for mechanical digestion), and the proventriculus, or glandular stomach (Figure 11--1), are located within the main mass of the bird's body. Less modification is evident in the avian small intestine and rectum; however, a cloaca is present as in reptiles.