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Digestive system part 2
 

Digestive system part 2

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    Digestive system part 2 Digestive system part 2 Presentation Transcript

    • about 25-cm -long muscular tubefunction : forwarding swallowed food fromthe pharynx down into the stomachits lumen is star -shaped, due to thelongitudinal reserve foldsthe typical structure of the alimentary canalappears in this segment
    • epithelium (lamina epithelialis mucosae):stratified, nonkeratinized squamousepithelium at its entire lengthlamina propria mucosae comprises cardiacesophageal glands (glandulae oesophageaecardiacae) in its begining and terminalportions; these glands resemble the cardiacglands, hence the name
    • cardiac esophageal glands produce neutral mucin,which protects the cells against the possible refluxof gastric juicein the lamina propria, there are scattered lymphaticelements, frequently in the vicinity of the excretoryductslamina muscularis mucosae is composed of mainlylongitudinal smooth muscle cells
    • is thrown into longitodinal folds, just likemucous membranethere are mixed or purely mucous smallsalivary glands, which are called esophagealglands proper (glandulae oesophageaepropriae)
    • in the upper one-third, striated muscle can befound, onlyin the middle approximately one-thirdsegments, the striated and smooth musclesare intermingledin the lower one-third, there are smoothmuscle cells, only
    • tunica adventitia is the outermost main layerof the esophagus; this layer connects themajority (cervical and thoracic portions) ofthe organ to the surrounding tissuethe abdominal portion , however , is replacedby tunica serosa (serous membrane)
    • bean -shaped hollow muscular organ of thegastro -intestinal tract involved in the secondphase of digestionit has four anatomical parts: cardia, fundus,body and pylorusit has three histological distinct parts: (1)cardia, (2) the fundus and the body have thesame histological properties, (3) pylorus
    • simple columnar epithelium invaginatesinto the lamina propria, thereby it makesgastric pits (foveolae gastricae)the tubular glands (cardiac -, fundic- andpyloric glands) of stomach empty into thebottom of the gastric pitsthe epithelial cells produce thick , neutralmucin , which protects the cells themselvesfrom highly acidic gastric juice
    • loose connective tissue, which may containmany lymphocytesall the gastric glands are located in this laminain the three histological portions of thestomach the glands display somewhatdifferent morphology ; their products are alsodifferent
    • a lamina muscularis mucosae well-developed, usually is composed of two sublayers of smooth muscle cells
    • loose coonecting tissue, containing blood vessels lymphatics lymphocytes solitary fat cells macrophages mast cells
    • contains smooth muscle cellscomposed of sublayers: outermost sublayer : discontinuous; comprise mainly longitudinally oriented smooth muscles cells, which may be absent from areas within the pyloric portion middle sublayer : circularly arranged smooth muscle cells, well-developed throughout the stomach ; the middle sublayer is greatly enhanced in the pyloric portion , where it is called pyloric sphincter muscle innermost sublayer : oblique bundles of smooth muscle cells may occur
    • The stomach is an intraperitoneal organ . Its outermost main layer is a serous membrane of loose coonective tissue and mesothelium towards the peritoneal cavity .
    • located in the lamina propria, which aredifferent in the histological portions: cardiac glands fundic glands pyloric glands
    • simple or branched glands, located in the cardiacportionthe secretory cells resemble the surface mucous cellsof the gastric pitsproduce mucin
    • branched tubular glandsseveral glands open into one gastric pithave segments in the upper segment ( neck ) neck mucous cells undifferentiated stem cells in the middle and lower segments (principal segment ) H Cl-producing parietal cells chief cells, which secrete pepsinogen enteroendocrine cells
    • in the pyloric region , the gastric pits aredeeper than in the other onesthe pyloric glands are branched tubularglands with curved endsthe secretory cells stain lightlythey produce mucin and antibacteriallysozymeentero -endocrine cells are also present