Digestive System Amd Excretory System

Breakdown of food into smaller pieces without chemical change to the food molecule

The breakdown of large insoluble molecules into small soluble molecules

Mechanical digestion: teeth che food to break into smaller pieces for larger SA to volume ratio Chemical digestion: salivary amylase break down starch Starch —> maltose

Passes blooded of food by peristalsis from mouth to stomach

1) contract muscular walls; churn to break up the food by mechanical digestion 2) produces protease enzyme for breakdown protein 3) produces HCl - maintain pH level for enzyme action and kills bacteria by acidic conditions which denature enzyme - product amino acid pH in stomach 2-3 acidic

Chemical digestion ; protease, amylase, lipase —> pancreas secreted into small intestine pH 8 alkaline Lipid digestion. Starts here

Makes bile to be secreted into the small intestine 1) neutralize the acid in the stomach to provide a suitable pH to work Neutralize acidic food from stomach 2) emulsifiers fats increasing surface area so enzyme can digest the more quickly

Lined with villi to increase surface area which absorption can take place 1) thin walls Speed up the rate of diffusion of molecules into the blood 2) rich blood supply Helps carry absorbed molecules away from intestine - always low concentration of food molecules in the blood maintain high conc gradient 3) increase. Length Increase SA 4) SURFACE area Villi increase surface area means digested food can be absorbed into the blood stream faster

Indigestible food passes through large intestine consist of the colon, rectum and anus remaining salts and water are absorbed Faecas stored in the rectum before removed

Filter small solute from the blood

Reabsorb water, ion and nutrients: removes toxins and adjust filtrate pH

Aqua poring allows water to pass from the filtrate into the interstitial fluid

Reabsorb Na+ and Cl- from the filtrate into the interstitial fluid

Selectively secrete and reabsorb different ions to maintain blood pH and electrolyte balance

Reabsorb solutes and water from the filtrate

Most urea Excess H2O Excess salts

All glucose Most H2O Some salts

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