Structure of the Stomach

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Transcript Structure of the Stomach

Structure of the Stomach
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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
Stomach Functions
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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
Stomach function 2
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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
Stomach function 3
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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
Stomach function 4
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Absorption:
Small lipid soluble substances are
absorbed in the stomach only.
Examples alcohol and asprin
Structure of the ileum
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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
Structure of ileum 2
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Between villi are glands = crypts of
Lieberkuhn
Crypts have:
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Goblet cells
Paneth cells – function is uncertain
Undifferentiated cells which divide rapidly
to replace cells on villi surface
Ileum functions
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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
Ileum Functions 2
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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.
Colon in Absorption
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Folded inner surface
epithelium 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
Pancreas
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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.
Lesson 5
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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