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GI > W2: Physiology of LI > Flashcards

W2: Physiology of LI Flashcards

(48 cards)

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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

Study These Flashcards
A

loss of K+ in diarrhoea

21
Q

Name 3 patterns of motility in LI

Study These Flashcards
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
Study These Flashcards
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

Study These Flashcards
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

Study These Flashcards
A

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

25
what is defecation reflex caused by
rectal stretch
26
two effects of activation of rectal stretch receptors
- 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
T/F most bacteria in gut are bad
False most bacteria in the gut are good 'commensals'
28
functions of gut commensals
- increased immunity by competing with pathogens - motility - synthesis of vitamin K2 and FFA - activate some drugs
29
where do intestinal gases arise from
- swallowed air | - bacteria in colon acting on indigestible carbohydrates
30
2 conditions of chronic bowel disease
irritable bowel syndrome | inflammatory bowel disease
31
presentation of IBS
Diarrhoea, constipation, abdominal pain
32
Treatment of IBS
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
two forms of IBD
Crohns- affecting whole gut | Ulcerative colonitis- affecting colon only
34
Treatment of IBD
Glucocorticoids for acute attacks (eg prednisolone) Aminosalicylates - maintance and mild disease
35
nervous innervation of internal anal sphincter
autonomic
36
nervous innervation of external anal sphincter
somatic (voluntary control)
37
what is the gastroileal reflex
prepares SI for chyme from stomach - relaxes ileocecal valve/sphincter - increased contractions in the ileum - delivery of chyme from ileum to caecum
38
what causes the gastroileal reflex
CCK and gastrin (increase ileum contractions and relaxation of ileocecal valve) and ENS
39
what cells in colon assist with require to damage
trefoil proteins
40
what is the rectosphincteric reflex
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
use of linaclotide
moderate to severe IBS (constipation form) but NOT IBD
42
Action and side effect of linaclotide
Increased Cl- and HCO3- secretion of interstinal fluid and increased interstinal transit increased bowel movements and reduced discomfort S/E= diarrhoea
43
use of Prucalopide
5HT4 receptor antagonist used in constipation which is resistant to other drugs (DONT use in Crohns)
44
use of Amitriptyline
resistant abdominal pain at low doses
45
Sulfazalazine
contains 5ASA not used in IBD used in Rheumatoid arthritis
46
mesalazine
releases 5ASA in the colon anti-inflammatory and immunosuppressant used in IBD treatment
47
olsalazine
two 5 ASA joined by azo bond (2N) Cleaved by bacteria
48
Balsalazide
yields 5 ASA following cleavage

GI (7 decks)

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