STOMACH It is made of 4 layers A

STOMACH

• It is made of 4 layers. • • A) Mucous membrane B) Submucosa C) Muscalaris externa D) Serous layer

Fundus of stomach • Mucous membrane; shows numerous folds or rugae on naked eye. • a) lining epithelium; columnar and mucous secreting. Epithelium dips into lamina propria to form the gastric pits. • • Deep to pits are the gastric glands.

Gastric glands • Types- main gastric glands, cardiac and pyloric. • Main gastric glands; numerous present in the fundus and body of stomach. These are absent in the pyloric region. • Chief cells, peptic cells or zymogen cells which are cuboidal or low columnar are seen in the basal part of the glands. • Cytoplasm is basophilic which have secretory granules and contain pepsinogen which is precursor of pepsin.

• Oxyntic or parietal cells; these are large, ovoid or polyhedral with central nucleus. Stain strongly with eosin and hence the name oxyntic. • Parietal cells lie against basement membrane. Under electronic microscope apical part of cells shows invaginations producing canaliculi which bear microvilli. • Oxyntic cells- secrete hydrochloric acid, produce intrinsoc factor which combines with vit. B 12 for its absorption.

• Mucous neck cells; large cells with clear cyrtoplasm, nucleus is flattened and pushed to the base. These are present near the upper end of the glands and secrete mucous. • Basal part of the glands are endocrine cells that contain neurosecretory granules. These stain with silver salts and hence called argentaffin cells. • These secrete harmone gastrin and 5 HT.

CARDIAC GLANDS • Present near the opening of oesophagus. These are mucous secreting, simple tubular or compound tubuloalveolar glands. • Gastric pits are shallow.

Pylorus • In the pyloric region of the stomach gastric pits are deep and the glands are mucous secreting. • Pyloric glands are simple or branched tubular glands. • Secrete harmone gastrin.

• b) lamina propria; made of connective tissue and occasional aggregation of lymhoid tissue which extends into submucosa called gut related lymhoid tissue (GALT). • C) Muscularis mucosa; well developed, has inner circular, outer longitudinal and an additional outer circular layer may be present.

• Submucosa; loose areolar tissue and has numerous blood vessels, lymphatics andnerve fibres. • Muscularis externa; oblique, circular and longitudinal layers from inside out. • Circlar fibres are greatly thickened to form the spincter at pylorus called pyloric spincter. • Outer most layer is serosa or adventitial layer.