wk 4 3 physiology pharmacology of large intestine

Question 1

3 longlitudinal strands in colon - taeniae coli, where does this change (circular muscle unchanged throughout)

Answer 1

rectum and anal canal - encircles

Question 2

what is the haustra

Answer 2

sac lik bulges in colon

Question 3

t/f there are no specialised functions in the caecum

Answer 3

true

Question 4

what hormones are required to open the gastroileal reflex

Answer 4

gastrin

CCK

Question 5

t/f gastroileal reflex relaxes in response to distension of stomach

Answer 5

false

relaxes in response to distension of duodenum

Question 6

what is a faecalith, what can it cause

Answer 6

obstruction of appendiceal orrifice

inflammation, leading to appendicitis

Question 7

outline main functions of colon 5

Answer 7

absorption - Na+, Cl- and H20 (condenses material)
- short chain fatty aciids (ones which arents absorbed by sml intestine)

secretion of K+, HCO3-, mucus

storage of colonic contents

periodic elimination of faeces

Question 8

difference in structure of sml and lrge intestine

Answer 8

colon - lacks villi, instead contains colonic folds, crypts (not lieberkuhn) , microvilli (incr surface a.)

Question 9

name for epithelial cells of colon, what do they mediate

Answer 9

colonocytes

electrolyte absorption (this drives water absorption)

Question 10

purpose of crypt cells

Answer 10

ion secretion

Question 11

what does gobleet cells of colon secrete

Answer 11

glycosaminoglycans (slippery surface barrier)

Question 12

t/f aldosterone enhances Na and K absorption

Answer 12

true

Question 13

when could significant loss of K occur

Answer 13

in diarrhoea

Question 14

3 types of motility in large intestine

Answer 14

haustration - non propulsive segmentation
peristaltic propulsion - mass movement
defaecation - pooing

Question 15

define haustration

Answer 15

saccules caused by alternating contraction of circular muscle (similar to segmentation of sml intestine, but slower)

Question 16

t/f haustration is directed towards anal canal from ascending colon

Answer 16

false

towards caecum

Question 17

name for what triggers mass movement

Answer 17

gastrocolic respone

involves gastrin and extrinsic nerve plexuses (para)

Question 18

define rectosphincteric reflex

Answer 18

relaxation of smooth muscle of internal anal canal due to passive rectal distension

Question 19

outline defaecation

Answer 19

mass movement (faecal filling rectum)) 
activation of rectal stretch receptors 
contraction of smooth sigmoid and rectum - internal anal relaxes (activates afferences to spinal/brain -urge, activates para efferents
relaxation of skeletal muscle of external

Question 20

hirschsprung disease is a defect in

Answer 20

rectosphincteric reflex

Question 21

t/f colonic flora can synthesis vitk1 and free fatty acids

Answer 21

false

vitk2 and free fatty acids

Question 22

define constipation

Answer 22

presence of hard dried faeces within colon (delay in defaecation, enhcances absoorption of H20

Question 23

hirschprung disease

Answer 23

devoid of intrinsic neurones

massive swelling due lack of neurones, cannot move distally - requires surgery

Question 24

associated symptoms of constipation

Answer 24

abdominal diiscomfort
headache 
loss of appetite 
malaise 
distension

Question 25

difference in laxatives and purgatives

Answer 25

lax - constipation
purg - promotes evacuation of both lrge nd small intestine, totally clearing bowels (endoscopic procedures, surgery ect require)

Question 26

when should laxativs not be used to treat constipation

Answer 26

if suspected physical obstrutcion

Question 27

how do laxatives work

Answer 27

increase peristalsis

and/or soften faeces

Question 28

t/f angina attack may be triggered by straining during defaecation

Answer 28

true

Question 29

3 medical uses for laxatives/purgatives

Answer 29

avoid straining in angina patients
clear bowel before surgery/endoscopy
treat drug-induced constipation/constipation in bed-ridden patients