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GI > Physiology of Large Intestine > Flashcards

Physiology of Large Intestine Flashcards

1
Q

Large Intestine is made up of?

A 
Caecum
Appendix
Colon- A,T,D,S
Rectum 
Anal canal
Anus
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2
Q

Describe the longitudinal smooth muscle of the large intestine?

A

3 Strands
Taeniae coli
Which unite around the sigmoid colon & thicken around the internal anal sphincter

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3
Q

Describe the Internal and external sphincters location and muscle?

A

Same location

2 rings of muscle= smooth and skeletal

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4
Q

What does the caecum recieve?

And what allows this entry?

A

1-2L of material made up of indigestible residues, unabsorbed biliary components and unabsorbed fluid from terminal ileum a day

Gastroileal reflex

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5
Q

What is the gastro-ileal reflex stimulated by?

A

Gatric distension

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6
Q

What does the gastro-ileal reflex involve?

A
  • Opening of ileocaecal valve (one-way valve)

- Opens inresponse to gastrin and CCK

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7
Q

What happens to caecum when duodenum is distended?

A

Relaxes

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8
Q

When does the caecum contract?

A

In response to distension of ascending colon

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9
Q

Describe the appendix?

A

Tube with extended lymphoid tissue connected to distal caecum via appendiceal orifice

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10
Q

What occurs when the appendiceal orifice is obstructed? And what obstructs it?

A

Appendicitis

Faecalith

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11
Q

What happens in the ascending and transverse colon?

A

Fluid reabsorption

Bacterial fermentation

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12
Q

What happens in the descending and sigmoid colon?

A 
Final drying (dessication) 
Storage
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13
Q

Functions of large intestine?

A
  • Absorption of H20, Na+ and Cl-
  • Secretion of K+. HCO3 and mucus
  • Absorption of short cahin fatty acids
  • Reservoir for colonic contents
  • Periodic elimination of faeces
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14
Q

There is a large amount of villi in colon. True or false?

A

False
No villi in the colon
There are colonic folds, crypts and microvilli (increased SA)

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15
Q

What do goblet cells do?

A

Secrete copious amounts of mucus containing glycosaminoglycans- which can form a barrier between bacteria laden faeces and the gut wall

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16
Q

Name for surface epithelial cells in colon?

A

Colonocytes

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17
Q

What do colonocytes do?

A

Mediate electrolyte absorption which by osmosis drives absorption of H20

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18
Q

Role of crypt cells?

A

Mediate ion secretion

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19
Q

What does mass movement in the colon involve?

A

Drives faeces into distal regions of colon
Triggered by meals
Simultaneous contractions of large sections of circular muscle of A&T colon drive faeces

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20
Q

What is haustration?

A

Non-propulsive segmentation (Contraction of circular muscle)
allows time for fluid and electrolyte reabsorption

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21
Q

What are haustra?

A

Sacules caused by alternating contraction of circular muscle

22
Q

What are peristalic propulsive movements?

A

Proximal colon drives faeces back towards caecum

23
Q

What occurs in the defecation reflex?

A
  • Mass movement (rectum fills with faecal matter)
  • Activation of rectal stretch receptors
  • Activation of pelvic nerve
  • Activation of afferents to spinal cord & activation of afferents to brain
  • Activates parasympathetuc efferents
  • Contraction of smooth muscle of colon and rectum (internal sphincter relaxes)
24
Q

The rectum is normally empty. True or False?

A

True

Not designed for storing faeces for prolonged periods

25
Q

Pudendal Nerve role?

A

Relaxation and contraction of external sphincter- controls defaecation

26
Q

What do colonic flora generally?

A

Increase intestial immunity by competition with pathogenic microbes

27
Q

Specific roles of colonic flora?

A
  • Promote motility
  • Synthesize vitami K2 + free fatty acids
  • Activate some drugs
  • Role in enterohepatic cycling of compounds
  • Beneficial (commensals)
28
Q

Causes of gas arising?

A
  • Swallowed air
  • Bacteria in colon which attack forms of carbs that are indigestible to humans
  • Gas that is not absorbed in LI is expelled through anus
29
Q

What valves separate gas from liquid?

A

Va,ves of Houston

30
Q

What is constipation?

A

Presence of hard dried faeces in colon - because faeces is in colon for too long a time and too much H20 is absorbed

31
Q

What causes constipation?

A
  • Ignoring urge to defecate
  • Decreased colonic motility (bad diet, drugs, netabolic disorders)
  • Obstruction of movement
  • Paralytic ileus after surgery
  • Impairmnet of motility/defecation reflex
32
Q

What is Hirschprung disease?

A

Absence of secretion of enteric nervous system

33
Q

What is IBS?

A

Irritable bowel syndrome

-Bouts of diarrhoea, constipation or abdominal pain

34
Q

Treatment fro IBS?

A

Largely symptomatic
Diet adjustment
Anti-diarrhoeals, Anti-spasmodics and laxatives

35
Q

Example of an anti-diarrhoeal?

A

Loperamide

36
Q

Examples of anti-spasmodics?

A

Alverine citrate
Mebeverine
Hydrochloride
Peppermint oil

37
Q

What is linaclotide?

A

Peptide drug for moderate to severe IBS with constipation in adults
NOT used in IBD
Increases chloride and bicarbonate secretion in intestinal fluid and also increases rate of intestinal transit

38
Q

Side affect of linaclotide?

A

Diarrhoea

39
Q

Drugs used in IBD?

A

5ASAa (5 aminosalicylic acid)
Glucocorticoids
Immunosippresants

40
Q

5ASAa?

A

5 Aminosalicylic acid
-Long term maintenenace of remission (more useful in UC)
-Sulfasalazine
Mesalazine

41
Q

What is sulfasalazine?

A

Reduces inflammation by inhibiting COX and LOX

Supplement with folic acid

42
Q

Side affects of sulfasalazine?

A

Rashes
Arthralgias
Blood dyscrasias

43
Q

What is mesalazine used in?

A

Only in distal disease ]Ulcerative collitis

44
Q

Mesalazine is better tolerated than sulfasalazine?

A

True - it is available in enemas

45
Q

What are glucocorticoids used for?

A

Acute attacks of IBD

46
Q

Examples of glucocorticoids?

A

Prednisolone

Budesonide

47
Q

What are glucocorticoids effective in?

A

UC
Crohn’s
Generally discontinued after remission because can cause dependency/resistance

48
Q

What drug is most frequently used for IBD?

A

Azothioprine

49
Q

When are immunosuppressants used to treat IBD?

A

Severe disease
Steroids don’t work
They inhibit T lymphocyte function & slow onset of action

50
Q

Examples of immunoseppressants?

A

Azothioprine
Ciclosporin
6-Mercaptopurine
Methotrexate

GI (15 decks)

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