Small Intestine Function Flashcards
what is the average total length of the small intestine?
6 meters
name three main functions of the duodenum
> gastric acid neutralisation
digestion
iron absorption
what makes up the majority of the small intestine the jejunum or the ileum?
the ileum (3.5cm long)
what part of the small intestine carries out the majority of nutrient absorption?
jejunum
what is the function of the ileum?
NaCl/H2O absorption: chime dehydration
what is the effect of the plica?
like a corkscrew they create a swirling pattern, so liquid swirls down the intestine
where are gut cells born?
in the crypts between the villi
what is contained in a villi?
> capillaries
> lacteals
by how much do the plicae increase the surface area of the intestine?
3 times
what structure increases the relative surface area of the intestine by 30 times?
the villi
by how much do microvilli increase the relative surface area of the intestine?
600 times larger
what do the villi cells absorb?
> NaCl > monosaccharides > amino acids > peptides > fats > vitamins > minerals > water
what do crypt cells secrete?
chlorine and water
what is transported into the cell via sodium coupled secondary transporters?
> glucose
galactose
amino acids
nucleosides
how much fluid does the small intestine secrete per day?
1500ml
where does h2o secretion come from?
epithelial cells lining the crypts of lieberkuhn
how is h2o secreted passively?
due to the active secretion of chloride into the intestinal lumen
why is h20 secretion important for normal digestive purposes?
> luminal contents is maintained in a liquid state
promotes mixing of nutrients and digestive enzymes
aids presenting nutrients to absorbing surface
dilutes and washes away potential injurious substances
name the transporter that transports chloride ion into the cell
sodium potassium chloride coupled transporter.
how does potassium leave the cell in regards to chloride ion transport?
through leaky k channels
how does sodium leave the cell in regards to chloride ion transport?
through sodium potassium channel
how is chloride transporter into the lumen from inside the gut cell?
through CFTR channel. ATP is converted to cAMP via adenylate cyclase. PKA then switches on the transporter allowing ions to be transported across
what are the two distinct types of movement in intestinal motility?
> segmentation
> peristalsis
when does segmentation occur?
during a meal
describe segmentation
there is contraction and relaxation of short intestinal segments. the contraction moves the chime into the relaxed segments which in turn contract and push the chime back. movement is quicker at the top of the intestinal tract so net movement is down.
what initiates the generation of segmentation contractions?
pacemaker cells in the longitudinal muscle layer
what produces oscillations in the membrane potential that brings the cell to threshold to allow the segmentation contractions?
the intestinal basic electrical rhythm
what determines the strength of the contractions?
the frequency of the action potential
what determines the frequency of segmentation?
the intestinal basic electrical rhythm
what is the effect of parasympathetic stimulation by the vagus nerve of segmentation?
increase in contraction
what Is the effect of the sympathetic system on segmentation?
decrease in contraction
what is the effect of the autonomic nervous system of segmentation?
none
when does peristalsis commence?
following the absorption of nutrients
what is migrating motility complex?
the pattern of peristaltic activity travelling down the small intestine (beginning in the gastric antrum)
where does the migrating motility complex end?
in the terminal ileum
what does the migrating motility complex aim to do?
> move undigested material into the large intestine
> limit bacterial colonisation
what hormone is involved in the initiation of migrating motility complex?
motilin
describe the contraction and relaxation of muscle in the small intestine if the smooth muscle is distended
> muscle on the oral side of bolus contracts
muscle on anal side relaxes
bolus is moved into area of relaxation
what neurons mediate peristalsis in the small intestine?
myenteric plexus
describe the gastroileal reflex
> ileocaecal valve opens
chyme enters the large intestine
colon distends
reflex contraction of the ileocaecal sphincter preventing back flux into the small intestine
