Digestive System

Oral cavity: Both physical and chemical digestion takes place in the mouth. Saliva is secreted to moisten food, protect the mouth from abrassions, buffer against acids in food, kill some forms of bacteria, and begin carbohydrate digestion with the enzyme SALIVARY AMYLASE.

Tongue is used for taste, manipulates food while chewing and prepares food for swallowing by forming it into a ball.

Pharynx is commonly called the throat. The intersection of the glottis and opening to the esophagus (gullet) is found here. The epiglottis is a flap that closes the glottis when the act of swalloing occurs.

Esophagus connects the pharynx with the stomach. Peristalsis, wave-like contractions of the smooth muscles push food down toward the stomach. Connects with the stomach at the cardiac sphincter.

Stomach is a J shaped expandable organ located on the left side of the abdominal cavity. It stores up to 2 liters of food while mixing and digesting it. The epithelial cells secrete Gastric juices and HCl making the pH around 2. Pepsin is an enzyme used to partially hydrolyze protein. Pepsin is released in an inactive form Pepsinogen. The pepsinogen reacts with HCl to form pepsin.

The hormone gastrin is secreted by the stomach cells to regulate the production of gastric juices. The stomach is closed at its posterior end by the pyloric sphincter.

Small Intestine: Most hydrolysis of macromolecules occur in the small intestine. It is more than 6 meters in length. It has smaller diameter than that of the large intestine.

It is divided into 3 sections (Duodenum, Jejunum, and ileum). Accessory Organs ( Pancreas, Liver, and Gall Bladder), add digestive enzymes, juices and hormones into the small intestine. As the acid chyme enters the duodenum (first 25 cm of the small intestine) a hormone called secretin is released from the intestinal walls to siginal the pancreas to release a bicarbonate solution which neutralizes the acid.

The hormone CHOLECYSTOKININ (CCK), is released...