Digestion

the taking in of substances into the body through the mouth

the breakdown of food into smaller pieces without chemical change to the food molecules

the breakdown of large insoluble molecules into smaller soluble molecules

the movement of small food molecules and ions through the wall of the intestines into the blood

the passing out of food that has not been digested or absorbed through the anus

Long-term energy storage Insulate the body Stored around vital organs Store certain fat soluble vitamins

Alimentary canal: begins at the mouth ends at the anus Digestive system: alimentary canal+ teeth+ salivary glands+ liver+ gall bladder+ pancreas

large insoluble molecules are broken down into smaller soluble molecules that can be absorbed and used by cells

Starch- salivary amylase Starch- pancreatic amylase Maltose- maltase glucose

contracts by muscular action to swallow bolus or push bolus to the oesophagus

Mechanical and chemical digestion

flap which closes over the windpipe

force food down through peristalsis

Prevents food from passing back

Sore excess glucose Breaks down excess amino acids

Absorb water Compact indigestible residue into semi-solid faeces

Store bile

Neutralize stomach acid Turn large fat globules to small fat droplets which increases the surface area for lipase

Secrete saliva with water and mucus to soften and lubricate food Contain salivary amylase

Masticated food rolled by tongue into the pharynx into the oesophagus

MD and CD Churn and mix food with gastric juice Some absorption HCl destroy bacteria found in food Contains pepsin

Secrete bicarbonate ions into the duodenum to completely neutralise and acids not neutralised by the bile

Absorption by villi Absorption of water CD and MD Starch to Maltose to glucose

Finger-like projection: extended surface area Micro-villi: increase surface area Dense network of capillaries: absorption of digested nutrients Single central lacteal: absorption of fat-soluble vitamins Single layer of epithelial cells: faster diffusion of nutrients, may mitochondria for active transport of nutrients