Human Digestive System 
Physical Digestion
Assimilation
Ingestion
Egestion
Chemical Digestion
Absorption
food is taken into the body
large pieces of food are broken up into smaller pieces of food
enzymes break down large, insoluble food molecules into smaller, soluble molecules
small, soluble molecules move from the gut into the bloodstream
molecules are used by the body, eg amino acids are used to build new proteins
undigested food leave the body through the anus
Mouth
Ingesting
Chewing
Increases the surface area of food
Food mixed with saliva
Saliva contains amylase which breaks down starch into maltose
Food moves down to the Oesophagus
Oesophagus
Carries food from mouth to stomach
Muscles on the walls contract behind the food to push it foward
Peristalsis
Stomach
Muscles churn food to aid physical digestion
secretes gastric juice which contains pepsin and hydrochloric acid
Pepsin is a protease enzyme which digests protein into amino acids
Hydrochloric acid serves 2 purposes:
- Kills bacteria
- Provides optimum pH for Pepsin
Food is released into the first part of the small intestine
which is called the duodenum
Small Intestine
Ileum
Large Intestine
Duodenum
Receives pancreatic juice and bile along with food
Both are alkaline
Contains enzyme maltase
Neutralises acidic food
Pancreatic Juice contains 3 enzymes:
- Amylase
- Lipase
- Trypsin
Amylase breaks down maltose into starch
Lipase break down lipids into fatty
acids and glycerol
Trypsin
break down protein into amino acids
Bile which stored in the gall bladder breaks up large drops of lipid into smaller
droplets
Increases the surface area for lipase to act upon
Emusification
Undigested food travels along the Colon
Absorb water, leaving out material called faeces
Faeces stored in the Rectum
Leaves through the anus (Egstion)
Breaks down maltose into glucose
Absorb food molecules to the bloodstream
High surface area
Villi
Each villus is 1-2 mm thick but there is thousands of them
Huge area of contact with food
Epithelial cells
Located along the wall of a villi
Microvilli to further increase surface area
Villi contains a network of blood capillaries
Absorb sugars and amino acids
transported away by
the blood flowing through the capillaries
maintains a concentration gradient
increase the rate of absorption