Figure 12.2: Peristalsis.    

c.Stomach: It is the widest organ of the alimentary canal. Figure 12.3 shows the anatomy of the stomach and Table 12.1 give the detail of enzymes. It is divided into two major parts 1) the body and 2) the antrum. Physiologically we can divide it into 1) the orad portion (first two third of the body) 2) the caudad portion (remainder portion of body and antrum). As food enters in the orad portion of stomach, it forms concentric circles. When food stretches the wall of stomach, vagovagal reflex travels from stomach to brain and back to stomach. Due to which the tone of muscular wall of stomach body reduces and the wall starts bulging out so that it accommodate greater quantity of food. In the completely relaxed stomach 0.8 to 1.5 litres food can occupy. After mixing of food with the stomach secretions, the resulting mixture is called chyme, further passes down the gut. Partial digestion of food (protein and fats) takes place here. It produce castle’s intrinsic factor which is required for the absorption of vitamin B12 to be absorbed through intestinal wall.