GI: The Large Intestine Flashcards
What factors influence the ileocaecal sphincter
It maintains a positive resting pressure
relaxed of duodenum distends
contracts if caecum distends
controlled by vagus nerve, sympathetic and enteric nerves
What is absobed in the large intestine?
Water
Sodium
Chlorine
Short chain fatty acids (cabohydrate not absorbed in small intestine is fermented by colonic flora to short chain fatty acids)
What is secreted by the large intestine?
postssium
Bicarbonate
Mucus
Where does reabsorbtion and fermentation primarily take place?
Acending and transverse colon
Where does desiccation and storage happen
Descendin and sigmoid
Give the three motions in the large intestine
Haustration
Peristaltic propulsive movements
Defaecation
What is haustration
haustra are saccules caused by contaction of the circular muscle and result in non propulsive segmentation
What is mass movement (peristaltic propulsive movements)
Simultaneous contraction of large sections of circular musce in the ascending and transverse colon (haustra dissappear) -drives faice into distal regions
What triggers mass movement
Gastocoli response involving gastrin and extrinsic nerve plexuses triggered by a meal
What nerve controls relaxation of skeletal mucsle of the external anal sphincter?
Pudendal nerve
What drives the reabsoption of water in the GI tract?
sodium transport from the lumen of the small intestine into the blood stream
What is contained in faeces?
100ml water
50ml cellulose, bilirubin and bacteria
What is diarrhoea?
Loss of fluid and solutes from the GI tract in excess of 500ml per day
What two ways can water move in the GI tract
Transcellular or paracellular
What reabsorption mechanism exist in the colon?
Epithelia sodium channels
