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Structure of the Stomach

Structure of the Stomach. Sac holding approx 5dm 3 Sphincter muscles at each end – cardiac and pyloric Mucosa folded forming gastric pits Epithelium of mucosa made up of columnar cells Goblet cells are within the columnar epithelium. Stomach Functions. Digestion:

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Structure of the Stomach

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  1. Structure of the Stomach • Sac holding approx 5dm3 • Sphincter muscles at each end – cardiac and pyloric • Mucosa folded forming gastric pits • Epithelium of mucosa made up of columnar cells • Goblet cells are within the columnar epithelium

  2. Stomach Functions • Digestion: • Gastric juice produced – contains hydrochloric acid • This acid kills most of the bacteria on the food. • Also in the epithelium are chief cells • Chief cells produce pepsinogen

  3. Stomach function 2 • Pepsinogen is a precursor of pepsin • Pepsinogen is not active • Converted to pepsin by removal of short chains of amino acids • These amino acids are removed by the action of HCl and the presence of pepsin

  4. Stomach function 3 • Gastric juice also contains lipase. • Lipase acts on triglycerides • Both pepsin and lipase have optimum PH’s of under 7 • Epithelium cells in the stomach are protected from the harsh acid conditions by the production of alkaline mucus by goblet cells in the epithelium

  5. Stomach function 4 • Absorption: • Small lipid soluble substances are absorbed in the stomach only. • Examples alcohol and asprin

  6. Structure of the ileum • Has tiny folds = villi • Villi made from the mucosa layer • Villus is 1mm tall • Cells on villi form microvilli or a brush border • Smooth muscle in the mucosa contract/relax to move villi in a sweeping action • Villi have v.good blood supply

  7. Structure of ileum 2 • Between villi are glands = crypts of Lieberkuhn • Crypts have: • Goblet cells • Paneth cells – function is uncertain • Undifferentiated cells which divide rapidly to replace cells on villi surface

  8. Ileum functions • Digestion: • Many enzymes that pass into the duodenum are still acting on food as it enters the ileum. • Many enzymes work when attached to the villi in the ileum • E.g. amylase attaches and entangles with carbohydrate in plasma membranes

  9. Ileum Functions 2 • This attachment of enzymes ensures that the products of digestion remain in close contact with the area of absorption • Villi epithelium also contain enzymes and expose active sites to outside of the cell • Most digestion occurs in epithelim of ileum rather than the lumen.

  10. Colon in Absorption • Folded inner surfaceepithelium is made from columnar cells with microvilli • Goblet cells • Function is to absorb inorganic ions and water • Ions absorbed by active transport water moves down water potential gradient

  11. Pancreas • Endo and exocrine gland • Endo – insulin and glucagon • Exo – pancreatic juice • Pancreatic juice travels down pancreatic duct to duodenum • Contains: Proteases, lipase, amylase, carboxypeptidase and hydrogencarbonate ions. • These hydrogencarbonate ions neutralise acidic mixture of blood.

  12. Lesson 5 • 1. add info to summary sheet from last time using WAQ/powerpoint • P7 make notes on role of liver, gall b and bile • Describe how following are absorbed in ileum – glucose, AA, FA and glycerol, water, ions, vitamins • Make notes on control by nervous system • SAQ 1.1 and 1.2 • H/W 1-3 p16

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