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: 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 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 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 Absorption: Small lipid soluble substances are absorbed in the stomach only. Examples alcohol and asprin

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

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

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

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.

Colon in Absorption 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 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 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