lecture 27 Flashcards
What is absorption?
the net passage of substances from the GI lumen across the lining of the intestine into the interstitial fluid or lymph
Where is the primary site of absorption?
Small intestine
Sites of absorption?
Mouth, oesophagus, stomach
Small and large intestine
What is absorbed at mouth, oesophagus and stomach?
lipid soluble substances
What is absorbs at small intestine?
90% of water and sodium, all nutrients
what is absorbed at large intestine?
9% of water and sodium
factors effecting absorption?
Motility
surface area
transport across epithelium
removal of interstitial fluid
what does correct rate of propulsion allow?
digestion and absorption
what exposes products of digestion to absorptive surfaces?
motility and segmentation
rate of absorption is proportional to?
surface area
what anatomic adaptions maximise surface area?
length of intestine
circular folds
villi
microvilli
what acts as a barrier between outside world and bloodstream?
intestinal epithelium
why is there so many microbiomes in GI tract?
the lumen of the intestine is continuous with the outside world
What are the two pathways of transport of molecules across epithelium?
paracellular gaps
cellular
what is the non-selective barrier that binds cells together?
tight junction
what is required for cells to do paracellular travel?
a concentration gradient
how many membranes do the solutes have to pass to reach blood or lymph?
two membranes, apical and basal
what reduces nutrients into their smallest possible units?
chemical digestion
benefits of transport proteins?
Absorb what is required
allows active transport
why is there a large blood flow to intestine?
for removal of substance from interstitial fluid
villi are arranged around?
blood vessels and lacteals?
how do you lose water?
Sweat, urine, faeces, breath
what is the total water delivered to small intestine?
~9-10L per day
What is the mechanism of water absorption?
osmosis
