Small Intestine Structure and Function Flashcards
what is the total length of the small intestine?
around 6 metres
how long is the duodenum?
25 cm
what is the functions of the duodenum?
Gastric acid neutralisation; Digestion; Iron absorption
how long is the jejunum?
2.5m
what is the function of jejunum?
nutrient absorption
how long is the ileum?
3.5m
what happens in the ileum?
nacl/h2o absorption -> chyme dehydration
how is the absorptive surface area enhanced?
by folds, villi and microvilli
what has the best absorptive surface area enhancement?
microvilli
what do villus cells absorb?
NaCl Monosaccharides Amino acids Peptides Fats Vitamins Minerals Water
what is the function of a crypt cell?
secretes cl and water
what can be coupled withsodiem in active transport?
glucose
galactose
amino acids
nucleosides
how much water does the small intestine secrete a day?
1500ml
why is water secretion important for normal digestive processes?
Maintains lumenal contents in liquid state
Promotes mixing of nutrients with digestive enzymes
Aids nutrient presentation to absorbing surface
Dilutes and washes away potentially injurious substances
what is the two disticnt types of movement?
segmentation
peristalsis
when is segmentation most common?
during meals
what is the function of contraction and relaxation of short intestinal segments?
moves chyme into adjacent areas of relaxation, then relaxed areas then contract and push chyme back.
this ensures thorough mixing of contents with digestive enzymes
what are segmented contractions initiated?
depolarisation generated by pacemaker cells in longitudinal muscle layer
what is the fequency of segmentation determined by?
basic electrical rhythm
what effects does parasympathetic ns have on contractions?
increases
what efects does sympathetic ns have on contractions?
decreases
whats the function of migrating motility complex?
Move undigested material into large intestine
Limit bacterial colonisation of small intestine
what hormone is involved in initiating migrating motility complex?
motilin
what nuerones mediate peristalsis of intestine?
myenteric plexus
what effect does gastric emptying have on segmentation activity in ileum?
increases
what effects does gastric emptying have on gastroileal reflex?
Opening of ileocaecal valve (sphincter)
Entry of chyme into large intestine
Distension of colon
Reflex contraction of ileocaecal sphincter (prevents backflux into small intestine)
