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1. Gastric Gland
Gastric Mucosa
> Gastric Epithelium: Throughout the stomach, the areas of the gastric epithelium which face the lumen of the stomach produce substantial amounts of mucus which covers the gastric wall and offers protection from the digestive gastric juice. The gastric epithelium also forms large invaginations into the Lamina Propria, creating gastric glands which are described in the next section.
> Gastric Lamina Propria: Is a fairly wide layer which accommodates the rather lengthy gastric glands and contains some lymphoid aggregates of MALT
> Gastric Muscularis Mucosa: Is a thin layer of smooth muscle cells which forms the border past which gastric glands do not extend.
Gastric Submucosa:
Is a relatively loose collagenous layer which conducts larger blood vessels.
Gastric Muscularis Propria:
The gastric muscularis propria, in addition to posessing an inner circular muscle layer and an outer longitudinal muscular layer common to all GI tract segments, also possesses an innermost muscle layer with an oblique geometry.
Gastric Adventitia
The adventitia of the stomach is composed solely of a layer of serosa which forms the gastric surface of the peritoneum.
2. Stomach
Mucosa
> Surface mucous cells: simple columnar epithelium
> Gastric pits: surface mucous cells
> Gastric glands: parietal, chief, enteroendocrine cells
> Lamina propria: connective tissue
> Muscularis mucosa: two smooth muscle layers
Submucosa
> Connective tissue, submucosal (Meissner’s) plexus
Muscularis externa
> Smooth muscle layers (longitudinal, circular, oblique), myenteric (Auerbach’s) plexus
Serosa
> Connective tissue, mesoderm
3. Pyloric Gland
The mucosal (pyloric glands) in this region look different to the gastric glands in the body of the stomach. The pits are deeper, and the glands shorter and more branched. There are fewer parietal cells, and most of the cells are mucosa secreting cells, which you can tell from the pale staining appearance. There are also some specialised enteroendocrine cells called G cells, mostly in the neck of the glands, which secrete the peptide hormone gastrin. Gastrin is secreted in response to the presence of food in the stomach, and it stimulates the secretion of pepsin and acid by the gastric glands. (The hormone will be transported in the local capillary system, and act locally). There are also neuro-endocrine cells (enteroendocrine cells) that secrete serotonin, and somatostatin (a regulating hormone that controls levels of insulin, glucagon, gastrin and growth hormone secretion).