digestion

• the function or the digestion system or alimentary canal is to break large insoluble molecules e.g starch into small soluble food molecules e.g sugars
• once digestion has been completed the body can absorb the small soluble molecules into the blood and transport them to the cells. in the cells the mitochondria carry out the process of respiration to release energy
• mechanical digestion: mechanical breakdown of food in the mouth by the teeth
• chemical digestion: chemical breakdown of food by enzymes
• chewing increases surface area of food exposing more food molecules to the enzymes. this makes digestion more efficient
• incisor: cut and slice into food

  canine: rip and tear food

  premolar: crush and grind food

  molar: crush and grind food
• tooth decay:

  1. food sticks between and on the teeh. bacteria feed on the food.
  2. bacteria release acid as they feed on the food
  3. the acid corrodes the enamel of the tooth
• eating less sugary foods prevents decay

  fluoride in toothpaste and drinking water helps to strengthen enamel against tooth decay

  brushing teeth twice a day prevents build up of plaque on teeth

  visit the dentist regularly to spot decay early which helps to prevent decay and toothache
• when we eat, we release saliva which contains enzymes,
• villi are finger like projections of the lining of the ileum which increase the surface area of the ileum, increasing the absorption of soluble food particles
• processes that happen in the digestive system:

  ingestion -> digestion -> absorption -> assimilation -> egestion
• mouth: saliva is mixed with food and food is mechanically broken down by teeth and chemically broken down by amylase
• oesophagus: food pipe which carries food to the stomach - squeezed along by peristalsis
• stomach: muscular bag where food is held so that there is time to digest it. the stomach produces enzymes and hydrochloric acid
• duodenum: more enzymes are added to continue digestion of large molecules
• ileum: digestion food is absorbed through the walls and enters the bloodstream
• colon: the colon absorbs water and some salts from the remaining unwanted food, forming faeces
• rectum: faeces are stored here before removal
• anus: opening through which faeces are egested