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GI (Y1) > Physiology and Pharmacology of the large intestine - Week 4 > Flashcards

Physiology and Pharmacology of the large intestine - Week 4 Flashcards

1
Q

How long is the large intestine?

A

1.7m

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2
Q

What is the approx diameter of the large intestine?

A

6cm

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3
Q

Explain the anatomy of the anal sphincters.

A

Internal anal sphincter composed of smooth muscle with external anal sphincter composed of skeletal muscle surrounding it

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4
Q

The taeniae coli and circular muscle layers in colon causes ‘sac-like’ bulges called…

A

Haustra

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5
Q

How is entry through the ileocaecal valve permitted?

A

by the gastroileal reflex in response to gastrin and CCK through the ‘one-way’ ileocaecal valve

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6
Q

How is the appendix attached to the caecum?

A

via the appendiceal orifice

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7
Q

What is absorbed in the colon?

A

Fatty acids, Na+, Cl- and H2O to condense ileocaecal material to solid, or semi-solid, stool

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8
Q

What is secreted in the colon?

A

K+, HCO3- and mucus

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9
Q

Which structures of the colon increase surface area?

A

colonic folds, crypts and microvilli

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10
Q

What are colonocytes?

A

Surface epithelial cells of the colon

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11
Q

What is the role of colonocytes?

A

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

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12
Q

Crypt cells mediate…

A

Ion secretion

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13
Q

What do goblet cells secrete?

A

copious mucus containing glycosaminoglycans – hydrated to form a slippery surface gel
trefoil proteins involved in host defence

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14
Q

Na+ absorption and K+ secretion are enhanced by…

A

Aldosterone

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15
Q

Which ion may be significantly lost in secretory diarrhoea?

A

K+

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16
Q

What are the 3 patterns of movement in the large intestine?

A

Peristalsis, defecation and haustration

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17
Q

What is meant by haustration?

A

Movement in the orad direction (towards the mouth) in order to increase absorption of fluid and electrolytes

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18
Q

Where does haustration occur?

A

Proximal colon

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19
Q

Haustration is regulated by…

A

Slow-wave activity

20
Q

What is meant by mass movement in the large colon?

A

simultaneous contraction of large sections (about 20 cm) of the circular muscle of the ascending and transverse colon (haustra disappear) - drives faeces into distal regions

21
Q

Mass movement is typically triggered by…

A

The gastrocolic response (involving gastrin and extrinsic nerve plexuses)

22
Q

Which reflex is triggered by mass movement?

A

Defecation reflex

23
Q

Which nerve sense activation of rectal stretch receptors?

A

Pelvic nerve

24
Q

Which nerve causes contraction of smooth muscle of sigmoid colon and rectum & internal anal sphincter relaxes?

A

Pelvic nerve

25
Q

Which nerve causes relaxation of skeletal muscle of external anal sphincter?

A

Pudendal nerve

26
Q

What is the role of colonic flora?

A

increase intestinal immunity by competition with pathogenic microbes
promote motility and help maintain mucosal integrity
synthesise vitamin K2 and free fatty acids (from carbohydrate) that are absorbed
activate some drugs

27
Q

Gases in the GI tract arise from…

A

Swallowed air or from bacteria in the colon

28
Q

Constipation results from…

A

delay in defaecation and enhanced absorption of H2O

29
Q

Give some causes of constipation.

A

ignoring, or suppressing, the urge to defaecate
decreased colonic motility (e.g. improper diet, drugs, metabolic disorders, old age)
obstruction of faecal movement
paralytic ileus following abdominal surgery
impairment of motility/defaecation reflex

30
Q

Symptoms of abdominal discomfort, headache, loss of appetite and general malaise associated with constipation are caused by…

A

prolonged distension of the large intestine

31
Q

What is meant by appendicoliths?

A

Hardened, calcified, faecal matter within the appendix

32
Q

Appendicoliths can cause…

A

Appendicitis

33
Q

What are purgatives?

A

agents that cause purging, or cleansing, of the bowels by promoting evacuation

34
Q

Laxatives and purgatives are contra-indicated when…

A

there is physical obstruction to the bowel

35
Q

How do laxatives work?

A

increase peristalsis and/or soften faeces

36
Q

Give some medically-sound uses of laxatives/purgatives.

A

Straining, painful defecation, to clear the bowel before surgery/endoscopy, to treat drug-induced constipation, or constipation in bedridden, or elderly patients

37
Q

What is the action of bulk laxatives?

A

Improve stool consistency. Slowly acting

38
Q

What is the action of Osmotic laxatives?

A

Rapidly acting laxative

39
Q

Give an example of a stimulant purgative.

A

bisacodyl

40
Q

What is the action of faecal softeners?

A

Detergent-like action

41
Q

What is the treatment for IBS?

A

with adjustment of diet and anti-diarrhoeals, anti-spasmodics

42
Q

Which class of drugs are used for treating acute episodes of IBD?

A

Glucocorticoids

43
Q

Give examples of glucocorticoids used in acute attacks of IBD.

A

prednisolone, budesonide

44
Q

Give the drug class used for maintenance of IBD.

A

Aminosalicylates

45
Q

Give examples of Aminosalicylates used for IBD.

A

Sulfasalazine, Mesalazine, Olsalazine

GI (Y1) (79 decks)

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