Human biology is a field in biology that deals with nutrition, anthropology, and medicine. The body of a human being contains a digestive system that deals with the digestion and absorption of food nutrients into the body. The stomach, small intestines, and large intestines are part of the digestive system. All of them are located at different positions in the body and have different functions and structures.

The Stomach

The stomach is an organ of digestion located between the esophagus and the duodenum on the left upper part of the abdominal cavity. It is a muscular, elastic pear-shaped bag lying just below the diaphragm. It is made up of five layers. The innermost layer is referred to as mucosa. The four sections of the stomach are the fundus, cardia, body, and pylorus. It is involved in the second phase of digestion after chewing. It secretes enzymes that help in the digestion of proteins. It also secretes some acids that help in the digestion of food. The major secretions are hydrochloric acid and protease enzymes. The work of hydrochloric acid is to kill any bacteria that may be in the food and provide an acidic pH that allows proteases to work effectively (Chiras 95).

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