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GI > W2: Physiology of LI > Flashcards

W2: Physiology of LI Flashcards

1
Q

contents of LI

A 
Caecum
appendix
ascending, transverse, descending and sigmoid colon
rectum
anal canal
anus
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2
Q

valve between ilium and caecum

A

ileocecal sphincter

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3
Q

describe the longitudinal smooth muscle in the caecum and colon

A

split into 3 strands: taeniae coli

circles the rectum and anal canal

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4
Q

describe muscle at the internal anal sphincter

A

smooth muscle is thickened at IAS

IAS is surrounded by skeletal muscle of EAS

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5
Q

what are haustra caused by

A

bulges caused by activity of taeniae coli and circular muscle layers

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6
Q

function of caecum and appendix

A

no function in humans

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7
Q

what is entry from ileum to caecum permitted by

A

gastroileal reflex (in response to gastrin and CCK)

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8
Q

What causes ileocecal sphincter to

a) relax b)contract

A

a-distension of duodenum

b-distension of colon

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9
Q

what innervates ileocecal sphincter

A

vagus nerves, sympathetics, enteric neurons and hormones

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10
Q

what is the appendix

A

blind-ended tube with extensive lymphoid tissue

connected to caecum by appendiceal orifice

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11
Q

potential cause of appendicitis

A

appendiceal orifice may be blocked by a faecalith

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12
Q

Functions of the colon

A
  • absorption of Na+, Cl-, H2O and small chain FA
  • secretion of K+, HCO3 and mucus
  • reservoir
  • Faeces elimination
  • carbs not absorbed in SI are fermented to short chain FA by colonic flora
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13
Q

in which part of colon does final drying and storage occur

A

descending and sigmoid

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14
Q

in which part of colon does fluid reabsorption and bacterial fermentation occur

A

ascending and transverse colon

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15
Q

what increases SA in colon

A

colonic folds
crypts
microvilli

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16
Q

name of surface epithelial cells of LI and their function

A

colonocytes

mediate electrolyte absorption (drives H20 absorption)

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17
Q

function of crypt cells

A

ion secretion

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18
Q

what do goblet cells in LI secrete

A
  • mucus containing glycosaminoglycans (gel)

- trefoil proteins (host defence)

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19
Q

what is Na and K absorption enhanced by

A

Aldosterone

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20
Q

electrolyte imbalance that diarrhoea can cause

A

loss of K+ in diarrhoea

21
Q

Name 3 patterns of motility in LI

A

Haustration- non propulsive segmentation
Peristaltic propulsive movements (mass movement)
Defaecation

22
Q 
what are hausta and what are they generated by
function of hausta
A
  • saccules caused by alteration contraction of circular muscle
  • disappear before and reappear after mass movement
  • generated by slow wave activity
  • mix content

(lower freq and longer time than segmentation)

23
Q

what is mass movement and how often does it occur

A

Simultaneous contraction of large sections of circular muscle in ascending and transverse colon (drives faeces to distal segements)

2/3 per day

24
Q

what is mass movement caused by

A

triggered by meal via gastrocolic response involving gastrin and extrinsic nerve plexus

25
Q

what is defecation reflex caused by

A

rectal stretch

26
Q

two effects of activation of rectal stretch receptors

A
  • to afferents of brain, urge to defecate, efferents to spinal cord
  • afferents of spinal cord, activates parasympathetic efferents, contraction of sigmoid and rectal smooth muscle, IAS relaxes

relaxation/contraction of skeletal muscle of EAS

27
Q

T/F most bacteria in gut are bad

A

False

most bacteria in the gut are good
‘commensals’

28
Q

functions of gut commensals

A
  • increased immunity by competing with pathogens
  • motility
  • synthesis of vitamin K2 and FFA
  • activate some drugs
29
Q

where do intestinal gases arise from

A
  • swallowed air

- bacteria in colon acting on indigestible carbohydrates

30
Q

2 conditions of chronic bowel disease

A

irritable bowel syndrome

inflammatory bowel disease

31
Q

presentation of IBS

A

Diarrhoea, constipation, abdominal pain

32
Q

Treatment of IBS

A

Largely symptomatic
adjustment of diet (increase soluble fibre, avoid insoluble fibre, emit gluten from diet)
anti-diarrhoeals (loperamide- increased segmentation, reduces perstalsis)
anti-spasmotics (reduce SM contraction eg alverine citrate)
Laxatives (except lactulose!!)
Anti-muscarinics (buscopan)

33
Q

two forms of IBD

A

Crohns- affecting whole gut

Ulcerative colonitis- affecting colon only

34
Q

Treatment of IBD

A

Glucocorticoids for acute attacks (eg prednisolone)

Aminosalicylates - maintance and mild disease

35
Q

nervous innervation of internal anal sphincter

A

autonomic

36
Q

nervous innervation of external anal sphincter

A

somatic (voluntary control)

37
Q

what is the gastroileal reflex

A

prepares SI for chyme from stomach

  • relaxes ileocecal valve/sphincter
  • increased contractions in the ileum
  • delivery of chyme from ileum to caecum
38
Q

what causes the gastroileal reflex

A

CCK and gastrin (increase ileum contractions and relaxation of ileocecal valve) and ENS

39
Q

what cells in colon assist with require to damage

A

trefoil proteins

40
Q

what is the rectosphincteric reflex

A

when passive rectal distension triggers relaxation the smooth muscle of the internal sphincter

if convenient to defecate, EAS relaxes
if inconvenient to defecate, EAS contracts

41
Q

use of linaclotide

A

moderate to severe IBS (constipation form) but NOT IBD

42
Q

Action and side effect of linaclotide

A

Increased Cl- and HCO3- secretion of interstinal fluid and increased interstinal transit
increased bowel movements and reduced discomfort

S/E= diarrhoea

43
Q

use of Prucalopide

A

5HT4 receptor antagonist
used in constipation which is resistant to other drugs
(DONT use in Crohns)

44
Q

use of Amitriptyline

A

resistant abdominal pain at low doses

45
Q

Sulfazalazine

A

contains 5ASA
not used in IBD
used in Rheumatoid arthritis

46
Q

mesalazine

A

releases 5ASA in the colon
anti-inflammatory and immunosuppressant
used in IBD treatment

47
Q

olsalazine

A

two 5 ASA joined by azo bond (2N) Cleaved by bacteria

48
Q

Balsalazide

A

yields 5 ASA following cleavage

GI (7 decks)

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