GI physiology 3- function of the small and large intestine

what is the importance of the contractions of the small intestine?

to mix the contents

ensure the luminal content contacts with epithelial cells

transports chyme along the tract

what are the 2 types of contractions in the small intestine?

segmentation

peristalsis

what is segmentation?

mixing movements

non-propulsive

what is the function of the migrating motility complex?

sweeps intestine clean between meals

removes bacteria and sloughed off epithelial cells

what is the function of ICC cells?

slow waves of smooth muscle

how is GI motility regulated?

an increase in parasympathetic vagal fibres increases contraction strength

the enteric nervous system controls strength of segmentation and peristaltic contractions

what is the structure of the small intestine?

folds of small intestine mucosa

mucosa is covered by villi

villi is covered by enterocytes with microvilli

what are the structures in an eneterocyte?

apical membrane

tight junctions

basolateral membrane

what are the 2 types of mechanisms?

transcellular

paracellular

what is the function of transcellular absorption?

organic nutrients are transported from intestinal lumen to the interstitial fluid across eneterocytes

what is the function of paracellular absorption?

inorganic ions and water diffuse through tight junctions connecting enterocytes

what happens during carbohydrate absorption?

glucose is absorbed via the NA-K-ATPase pump

monosaccharides are transported via the portal vein to the liver where they are stored as glycogen

what happens during luminal phase digestion?

multiple enzymes are secreted by gastric glands and pancreas

results in mainly small peptide chains and some amino acids

what happens during membranous phase digestion?

peptidases located at the membrane of enterocytes or intracellularly act on peptides

produces amino acids

what are the 4 phases of lipid assimilation?

emulsification

hydrolysis

micelle formation

absorption

what is formed in the kidneys when calcium requirements are high?

more calcitriol

how is sodium absorbed?

co-transport with glucose out of the gut

how is potassium absorbed?

mainly by paracellular passive diffusion

where does the large intestine absorb water and ions from?

chyme

what are the 4 types of contraction in the large intestine?

segmentation

peristalsis

antiperistalsis

mass movements

what is the function of antiperistaltic contractions?

forces material to accumulate in proximal portions

allows for intense mixing

a pacemaker in the pelvic flexure

what are the 2 caecal contractions?

segmentation

mass movements

how are gases produced by fermentation removed?

peistalsis

where is the pelvic flexure in horses?

between ventral and dorsal parts of the colon

what is diarrhoea caused by?

increased secretion and/or reduced absorption

when does malabsorptive diarrhoea occur?

when absorption is inadequate to recover a sufficient portion of secreted water

when does hypersecretory diarrhoea occur?

when the rate of intestinal secretion increases and overwhlems the absorptive capacity