1. Stomach:- It is both exocrine & endocrine organ that digests food & secretes hormones. It is a dilated segment of the digestive tract. The main functions of the stomach:- 1. Continuation of digestion of carbohydrates initiated in the oral cavity (mouth) by salivary amylase which starts the digestion of carbohydrates & this process will continue in the stomach. 2. Secretion of acids (HCl) together with the muscular activity of the muscles of the stomach will transform the digested food into a viscous mass known as chyme. 3. The stomach initiates the digestion of proteins by the enzyme pepsin so the stomach secretes pepsinogen which is converted into pepsin which initiates the digestion of proteins. 4. The stomach secretes or produces gastric lipase. Gastric lipase starts the digestion of triglycerides together with the help of lingual lipase.

2. Types of gastric glands:- 1) The cardiac glands:- are present in the cardiac region. They are simple or branched tubular glands, lined by mucus secreting columnar cells similar to the mucous neck cells of the gastric gland proper. They secrete mucus & lysozyme. 2) Fundic glands (gastric gland proper):- are present in the lamina propria of the fundus & body of the stomach. They are branched, tubular glands, 3 to 7 of which open into the bottom of each gastric pit. The glands are composed of the following cells:- a)Mucous neck cells:- are located between the parietal cells in the neck of the gland. The cells are large irregular in shape, with clear cytoplasm & the nucleus is flattened at the base of the cell. They secrete mucus which protects the stomach wall from the action of the HCl & proteolytic enzymes.

3. b) Peptic (chief or zymogenic) cells:- they predominate in the lower part of the gland & have all the characteristics of the protein synthesizing & exporting cells. Their basophilia is due to the abundant RER (rough endoplasmic reticulum). The granules in their cytoplasm contain the inactive enzyme pepsinogen, the precursor of pepsin. c) Parietal (oxyntic) cells:- are present mainly in the upper half of the gland. They are large rounded or pyramidal cells with one centrally placed spherical nucleus & intensely eosinophilic cytoplasm. d) Enteroendocrine cells:- were formerly called argentaffin & enterochromaffin cells, owing to their affinity for silver & chromium stains

4. 3) Pyloric glands:- are present in the pyloric region of the stomach & are similar to the cardiac glands. However, the pits are longer & the glands are shorter & coiled, opposite to that of cardiac glands.

5. Regions of the stomach and their histological structure