Stomach

Stomach:
The stomach connects the esophagus to the intestines and in the most species serves not only to continue the breakdown of foodstuffs via the use of digestive enzymes and acid but it also as a storage depot for food. Usually food remains in the stomach a few hours during which it is converted into a liquid material, called chyme.
Regional variation in the glands of the tunica mucosa of the stomach
Not all regions of the stomach mucosa have the same histological structure. They vary as follows:
•cardia: contains many mucus-secreting glands
• fundus: mostly glands secreting acid-peptic gastric juices; some
mucus-secreting glands
. pylorus: contains different types of mucus-secreting glands.
Wall of the Glandular Stomach
mucosa: in the empty stomach, this layer is thrown into deep longitudinal folds called rugae that extend from the lamina muscularis mucosae to the lumen; in the full stomach the rugae are much reduced in size as a result of distension of the tunica mucosa to accomodate the presence of a large amount of food material
• submucosa: typical loose connective tissue contains parasympathetic ganglia located in submucosal plexuses also known as Meissner’s plexuses
musculris externa: typical smooth muscule consisting of at least two layers, an inner circular layer and an outer longitudinal layer; parasympathetic ganglia located between the two muscle layers in
Layers of the Mucosa of the Stomach - Fundic Region . *Epithelia : consists of simple columnar epithelium that forms branched tubular gland, organized into gastric pits that open onto the lumen and gastric glands that empty into the base of the gastric pits.
*Lamina propria: consists of loose areolar connective tissue that in the glandular stomach is minimal between gastric glands and difficult to see in sections; highly vascular containing many blood and lymphatic capillaries
*Muscularis mucosac: consists of several, layers of smooth muscle oriented both longitudinally and circularly usually not very thick.
cell types in the gastric gland:
* Surface mucous cells: line the gastric pit and secrete mucous and bicarbonate ions to protect the epithelium from digestion by gastric juice ( contains HCL and pepsin ) present in the stomach lumen . *Neek mucous cell : found dispersed between the parietal cells ;secret a mucous that is thinner than secreted by the surf ace mucous cell ; mucus protects other glandular cell from action of proteases and HCL .
Parietal cells : found throughout the gastric gland round cells that contain distinct eosinophilie(pink) cytoplasm and round prominent nucleus ; secrete HCL and intrinsic factor needed for absorption of vitamin B12 .
Chief (peptic , zymogenic ) cell : found mostly near the base of the gastric gland ; very basophilie (purple) containing basally positioned nucleus and prominent basophilie apical cytoplasm filled with many ribosomes; secrete pepsinogen which is converted to pepsin in the acidic milieu of the stomach.
Enteroendocrine cells : difficult to distinguish by conventionl light microscopy , several types are present some secrete serotonin , gastrin , glacagon somatostatin among other hormones .
Pylorus region:
Simple columnar mucous epithelium lines the surface of the stomach extends into and lines the gastric pits ,as in the cardia region only one type of cell is normally found in these glands this is tall columnar
Cell , with slightly granular cytoplasm1ight1y stained because of mucien content and flattened or oval nucleus at the base.
The remaining structures in this region are similar to those in the fundus