Sistema Digestório do Gallus gallus - Da orofaringe à moela

Abstract

The digestive system of the domestic chicken presents physiological adaptations related to its diet. Highlighting these adaptations and demonstrating the morphofunctional aspects of the oropharynx, esophagus, proventriculus, and gizzard was the objective of the video developed by academics from the extension project "Knowing, respecting and producing birds: didactic and alternative models in the teaching and learning process," linked to the discipline Comparative Anatomy of Domestic Animals (BA066) of the Zootechnics Course at the Federal University of Paraná (UFPR). Sequentially to the oropharynx, the alimentary canal begins; the first segment is the esophagus, a muscular-membranous tube responsible for conducting food from the oropharynx to the proventriculus. In birds, it is characterized by a ventral dilation in its cervical portion, called the crop ("ingluvies"). Its walls have smooth muscle and a mucosa rich in glands; in pigeons, there is a secretion of whitish lipid content that gives it the name "crop milk." Its main function is to act as a temporary reservoir where food is moistened and softened, and where slight fermentation of grains may occur. Sequentially, the esophagus leads to the proventriculus ("chemical stomach"), important for the production and secretion of gastric juice (hydrochloric acid and pepsinogen), which are crucial for the chemical digestion of ingesta. After chemical digestion, the food is directed to the gizzard ("gastric ventriculus" or "mechanical stomach"), characterized by thick, highly muscular walls, and internally a layer known as the horny cuticle, which provides rigidity and protection against abrasion caused by small stones and ingested particles. The gizzard is considered one of the most specialized organs in birds, responsible for the intense grinding of food before its passage to the intestine, thus contributing to the mechanical reduction of food, since birds do not have teeth like mammals.