Where are the saliva, gastric juice, and bile secreted? What is the use of each in digestion?
a.) Saliva is secreted in the mouth by the salivary glands. Saliva is a somewhat alkaline fluid that moistens the mouth, softens food, and aids in digestion. The submaxillary glands are located around the mouth under the lower jaw, the sublingual glands are located beneath the tongue, and the parotid glands are found in front of each ear. The buccal glands, in the cheeks near the front of the mouth, also secrete saliva. b.) Gastric juice is a thin, strongly acidic (pH varying from 1 to 3), almost colorless liquid secreted by the glands in the lining of the stomach. Its essential constituents are the digestive enzymes pepsin and rennin, hydrochloric acid, and mucus. Pepsin converts proteins into simpler, more easily absorbed substances; it is aided in this by hydrochloric acid, which provides the acid environment in which pepsin is most effective. Rennin aids the digestion of milk proteins. Mucus secreted by the gastric glands helps protect the stomach lining from the action of gastric
