Structure of the Stomach

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 PHs 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