Physiology: large intestine 2

Question 1

how is SA increased in the colon

Answer 1

by colonic folds, crypts and microvilli

Question 2

describe the role of colon surface epithelial cells(colonocytes)

Answer 2

mediate electrolyte absorption which, by osmosis, drives absorption of H2O

Question 3

what is the role of crypt cells in the colon

Answer 3

mediate ion secretion

Question 4

describe the role of goblet cells in the colon

Answer 4

secrete copius mucus and secrete trefoil proteins

Question 5

what effect does aldosterone have on transepithelial movement of electrolytes

Answer 5

enhances Na absorption and K secretion

Question 6

describe the role of haustration

Answer 6

mixes content and allows for fluid and electrolyte reabsoprtion

Question 7

when do haustra appear and disappear

Answer 7

disappear before and reappear after mass movement

Question 8

describe the act of mass movement(peristaltic propulsive movement)

Answer 8

simultaneous contraction of large section of circular muscle of ascending and transverse colon

Question 9

describe the role of mass movement

Answer 9

powerfully drives faeces into distal regions

occurs 1-3 times a day

Question 10

what is mass movement typically triggered by

Answer 10

after a meal via gastrocolonic response, involving gastrin + extrinsic nerve plexuses

Question 11

what is activation of rectal stretch receptors caused by and what does it do

Answer 11

cause = faeces in rectum
function = activated afferents to brain and urge to defaecate

Question 12

give 2 beneficial functions of the colonic flora

Answer 12

increase intestinal immunity

promote motility

Question 13

what do intestinal gases arise from (3)

Answer 13

swallowed air, bacteria in colon and gas not absorbed