1. Digestive system

2. Stomach
Is dilated part of GIT whose main function is to continue the digestion of carbohydrate by adding an acidic fluid to the ingested food which is transformed into (chyme) ,
digestion of protein
and the digestion of triglandyceride .Stomach is formed from 4 regoins : Cardia , fundus , body and pylorus .The mucosa and submucosa form a longitudinal folds called rugae .

3. Stomach

4. Mucosa
The mucosa consists of surface epithelial which is simple columnar epithelial , that invaginate into the LP , forming gastric pits . Emptying into the gastric pits are branched , tubular glands (cardiac ,gastric and pyloric ) .The LP is composed from loose CT with few smooth muscles fibers and lymphoid cells . Muscularis mucosa is a layer of smooth m which separate the mucosa from submucosa .

5. The surface epithelial secrete mucous (alkaline mucous ) which form a protective gel , that is firmly adherent to the epithelial surface .
The epithelial also secrete bicarbonate which form a PH gradient ranging from 1 at the gastric lumen to 7 along the surface epithelial .
The ionic transport also maintain the acidic PH
The intercellular tight junction and
The profuse circulatory bed in the submucosa which are important to form a line of defense .

6. Cardia :
Fundus and body:
The LP of fundus and body is filled with branched , tubular gastric (fundic) gland , three to seven of which open into each gastric pit .Each gastric gland has three distinct regions : the isthmus , neck and base .
The isthmus is close to the gastric pit , contain differentiated mucous cells that will migrate and replace superficial mucous cells , undifferentiated stem cells , and Oxyntic (parietal) cells ,
The neck consists of stem cells , mucous neck cells (differ from the mucous cells in the isthmus ) and parietal cells ,
The base contains parietal and chief (Zymogenic cells) .
Enteroendocrine cells are dispersed in the neck and the base of the gland .

7. Stem cells :
Found in the isthmus and neck regions , these cells have a high rate of mitosis , some of them move upward to replace the pits and surface mucous cells , other migrate deeply into the gland and differentiate into mucous neck cells and parietal , chief , and enteroendocrine cells .
Mucous neck cells :
Are present in the neck of the gland their mucous is quite different from that of the surface mucous cells .

8. Oxyntic (parietal) cells :They are rounded or pyramidal with one centrally located nucleus and intensely eosinophilic cytoplasm due to the presence of high number of mitochondria , they are deep invagination of plasma membrane forming the intracellular canaliculus .
When stimulated to produce H+ and cl- tubulovesicular structures fuse with the cell membrane to form the canaliculus and more micrivilli . Pareital cells secrete hydrochloric acid (H+ and cl- ) , Kcl and gastric intrinsic factor .
The secretary activity of parietal cells is initiated by the cholinergic nerve endings , histamine and gastrin which are secreted by the mucosa .
Pernicious anemia

9. Chief (Zymogenic )cells :
These cells are predominant in lower parts of tubular gland , have the criteria of protein secreting cells , their basophilia is due to the abundant RER ,the granules inside their cytoplasm contain pepsinogen which convert rapidly into high active proteolytic enzyme pepsin .In human chief cells also produce lipase .

10. Enteroendocrine cells
They belong to Diffuse Neuroendocrine System (DNES). It is believed that each cell is capable of secretion of only one hormone. The target of these hormones are in the vicinity of their release, therefore, these hormones are called as (paracrine hormones)
In the stomach, these cells are found in the neck and bases of gastric gland. In the fundus, serotonin is one of the important secretary products.
Tumor called carcinoid syndrome which arise from these cells, are responsible for the clinical symptoms caused by over production of serotonine (flushing, abdominal cramps, dyspnea, increases gut motility)

11. action Location Hormone
Contraction of Gall bladder, release of pancreatic enzyme
Small Intestine (SI)
Cholecytstokinin (CCK)
Inhibits secretion of HCl SI
Gastric inhibitory peptide
Stimulates secretion of HCl, and gastric enzymes
Stomach and duodenum
Gastrin
Stimulates glycogenolysis by hepatocytes
Stomach, SI and Large I
Glicentin
Glucagon
Increases intestinal peristalsis
Motilin
Decreases peristalsis in intestine, stimulate blood supply to ileum
Neurotensin
Stimulates secretion of bicarbonate by pancreas
Secretin
Serotonin
Inhibits DNES cells in its vicinity of release
Somatostatin
Substance P
Inhibits secretion of HCl, increase epithelial mitosis
Duodenal (Brunner gland)
Urogastrone
Increases intestinal peristalsis, stimulates secretion of ions and water by the alimentary canal
Vasoactive intestinal peptide

12. The pylorus
has gastric pits into which the branched ,tubular pyloric glands open , compared with the gland in the cardia , pyloric gland have longer pits and short coiled secretary portions . These gland secrete mucous and lysozyme . Gastrin (G) cells are enteroendocrine cells located among mucous cells , G cell secrete Gastrin hormone which in turn activate parietal cells to secrete Hcl , other enteroendocrine cells are D cells which secrete somatostatin which inhibit the release of other hormones including Gastrin .

13. Other layers of stomach
The submucosa.
The muscularis composed from three layers of smooth mm outer longitudinal , middle is circular and the inner is oblique .
At the pylorus the middle layer is thickened to form the pyloric sphincter , the stomach is covered by a thin serosa .

14. Thank you