INTRODUCTION
Food starts to be digested and absorbed in the stomach, although absorption is mostly limited to water, alcohol and some drugs. The stomach is an expandable, muscular bag, and it keeps swallowed food inside it by contracting the muscular pyloric sphincter. Food can stay in the stomach for 2 hours or more. Food is broken down chemically, by gastric juice, and mechanically, by contraction of the three layers of smooth muscle in the muscular external layer. The broken up food at the end of this process is called chyme. Gastric juice is secreted by gastric mucosal glands, and contains hydrochloric acid, mucus, and proteolytic enzymes pepsin (which breaks down proteins), and lipase (which breaks down fats). It normally expands to hold about one litre of food. The stomach of a newborn human baby will only be able to retain about 30 millilitres (Sherwood and Lauralee 2007). When the stomach is empty, and not distended, the lining is thrown up into folds called rugae. After eating, these folds flatten, and the stomach is able to distend greatly. The stomach has three anatomical regions: cardiac, which contains mucous secreting glands (called cardiac glands) and is closest to the oesophagus fundus, the body or largest part of the stomach which contain the gastric (fundic) glands pyloric, which secretes two types of mucus, and the hormone gastrin (Brunicardi, Charles and Dana, 2010).
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