digestive system Flashcards
what is ingestion
taking food in through the mouth and swallowing
what is digestion
breaking down large insoluble molecules in food into smaller, soluble molecules
what is absorption
movement of small soluble molecules out of the gut and into the blood by diffusion and active transport
what is egestion
passing out undigested food through the anus
what is assimilation
building larger biological molecules from the small soluble molecules, in all calls
where does ingestion take place
mouth
what types of digestion happen in the mouth
mechanical and chemical
what is mechanical digestion
food is broken up into smaller pieces by chewing. this increases the surface area for enzymes
what is chemical digestion in the mouth
saliva in mouth releases amylase which breaks down starch into maltose
what does amylase do
turn starch into maltose
what is the food made into before swallowing
a bolus
how is food pushed down the oesophagus
peristalsis
what is peristalsis
wave like contractions causing the oesophagus to widen and pushes food down oesophagus
where is pepsin released from
gastric glands in stomach
what does pepsin do
turns proteins into peptides
why does the stomach also release hydrochloric acid
to ensure an acidic pH for pepsin to be at optimum conditions and kill bacteria
what happens in the duodenum
final site of chemical digestion of starch, protein and lipids
where are trypsin, amylase and lipase released from
pancreas
what does trypsin do
turns proteins to peptides
what does lipase do
turns lipids into glycerol + 3 fatty acids
what does the duodenum wall release
maltase and peptidase
what does maltase do
turns maltose into glucose
what does peptidase do
turns peptides into amino acids
where is bile produced
liver
where is bile stored
gall bladder
what does bile do
1 - neutralises stomach acid to 7-8 in duodenum
2 - emulsifies lipids - breakdown large droplets into smaller, increasing SA for lipase to digest
what happens in the ileum
absorption
where are soluble molecules absorbed
villi - through diffusion and active transport
how are villi adapted for diffusion
- large SA from folding of microvilli
- short diffusion distance - 1 cell thick wall
- high concentration gradient - lots of capillaries
