Wastes are removed by defecation as initiated by stretching of the rectal walls. The various salivary glands add water, electrolytes, mucous and salivary amylase to the food as it is chewed. Secretory cells filter and modify the blood to produce saliva. In humans these secretions are mostly water. Parotid, submaxillary, sublingual glands add saliva to the food during mastication.
Salivary amylase begins the breakdown of carbohydrates while the food is still in the mouth.
Salivary lysozyme lyses bacterial cell walls. Mucopolysaccharides act as lubricants and the water acts to extract flavors from food. Salivary secretion is controlled by the nervous system. Gastric glands are present throughout the mucosa of the stomach. The mucous acts to protect the gastric lining from the acid and enzymes present.