diet and digestion Flashcards
key adaptations of the villi
- large surface area (villi and microvilli)
-> increases rate of diffusion - good blood supply
-> maintain concentration gradient of blood - lacteal absorbs lipids
- long
-> lots of chance for diffusion to occur - thin/near capillary
-> short diffusion distance
what is assimition
small food molecules are used to build larger molecules (e.g. amino acids are used to synthesise proteins)
what is absorbtion
small, soluble molecules move from the small intestine to the blood
what is ingestion
food enters the digestive system via the mouth
what is egestion
removal of undigested food (faeces) from the anus
what is digestion
breakdown of large insoluble molecules into small soluble ones
what is mechanical digestion
teeth break down food into small pieces and peristalsis helps to move food along
what is chemical digestion
enzymes break down food to small soluble molecules
what is the order of digestion
mouth -> oesophagus -> stomach -> duodenum -> ileum -> colon -> rectum -> anus
function of salivary glands
produces saliva
-> helps to moisten food
-> contains enzyme salivary amylase which starts the breakdown of food
function of the mouth
food is ingested
mechanical digestion occurs here - teeth cut and crush food into smaller pieces which increases the surface area for enzymes to work
food is mixed with salivary - contains digestive enzymes (salivary amylase) to break down starch and moisten food
form a bolus of food which is pushed to the back of the mouth using the tongue
function of the teeth
involved in mechanical digestion (physical breakdown of food)
incisor - for cutting and biting
canine - for holding and cutting
premolar and molar - for crushing and chewing
function of the oesophagus
food passes down oesophagus and into the stomach
food is moved through the digestive system via peristalsis
- circular and longitudinal muscles involved to produce wave-like contractions
function of the stomach
muscular bag that stores food for several hours
secrete HCl which makes stomach very acidic - the acid kills bacteria so you don’t get food poisoning and provides optimum pH for pepsin
produces the enzyme pepsin, which breaks down proteins to dipeptides
muscles in the wall of the stomach contract and churn the food
function of the liver
filters toxins from the blood
acts like a food processing factory and will break down some molecules and build/store others
produces bile which emulsifies lipids
function of the gall bladder
stores bile and releases bile into bile duct to enter the duodenum
in the duodenum bile has two roles:
- neutralising acids
- emulsifying lipids
function of the pancreas
produces trypsin, lipase, pancreatic amylase
these are released into duodenum for chemical digestion