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BRS > gastroenterology - large bowel > Flashcards

gastroenterology - large bowel Flashcards

1
Q

What does the large bowel consist of?

A

colon (ascending, tranverse and descending)

caecum

appendix

recturn

anal canal

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2
Q

What is the caecum?

A

blind pouch just ditsal to ielocecal valve (connects ileum to colon)

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3
Q

what types of organisms have larger caecum?

A

herbivors

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4
Q

what is the appendix?

A

thing extention of caecum , not relevant in humans

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5
Q

what are main function of large bowel?

A

reabsoprtion of electrolyes and water

elimination of undgiested food and waste

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6
Q

what are the 4 types of colon?

A

asending- right side runs from caecum to the hepatic flexure, turn of colon by liver

transverse colon - from hepatic flexure to splenic flexture

hangs off the stomach, attached by greater omentum

descending - from splenic flexure to sigmoid colon

sigmoid colon - S shaped descending colon to rectum

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7
Q

What is the blood supply to colon?

A

proximal transverse - middle colic artery

distal 3rd transverse colon - inferior mesenteric artery

regions between the 2 senstive to ischemia

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8
Q

what is the perotenium?

A

layer surroding colon

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9
Q

Where are nodules of lymoid tissues common?

A

walls of distal small intestine - pyere’s patch

large intestine - solitary nodules

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10
Q

what is the strucutre of the peritoneum?

A

fatty tags - appendices epiploicae

and muscle coat with 3 bands (taeniae coli)

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11
Q

What is function of taenia coli?

A

large intestine motlity

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12
Q

Why do large intestine have their appearance as it is?

A

taenia coli are shorter

so forms pouched ovoid segments called hasutra

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13
Q

where does more abosrption take place in colon?

A

proxmial colon

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14
Q

how do large intestines absorb water?

A

Na+ and CL- absorbed by exchange mechanisms and ion channels

water follows by osmosis

K+ moves passively into lumen

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15
Q

What is the rectum strucutre?

A

dilated distal portion of alimentary canal

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16
Q

how is rectum distringushed from colon?

A

by transverse rectal folds in its submucosa and absence of taenia coli in its musclaris externa

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17
Q

what muscles is the anal canal surronded by?

A

internal (circular muslce)

external (striated muscle)

anal sphincters

18
Q
A
19
Q

What 4 layers in the large bowel made from?

A

mucosa, submucosa, muscularis, serosa

20
Q

which layer habours myetenric plexus?

A

serosa

21
Q

which 2 layers have glands?

A

mucosa and submucosa

22
Q

what are similarties between mucosal layer of small and large intestine?

A

entercoytes (abosrb cells) and goblets (secrete mucus) are abudant

a lot of crypts - stem cells

23
Q

Why does mucosa appear smooth?

A

as have no villi

24
Q

what is important about strucutre of entrocyes?

A

have short irregular microvilli - concerned resportion of salt

25
Q

what has more goblet cells large or small bowel?

A

large

26
Q

Where are they more prevelant in large bowel?

A

in crypts than along the surface

and increase distally towards rectum

27
Q

what is charactistic of goblet cell?

A

apical ends are packed with mucus filled secretions granules awaiting release

28
Q

Why is mucus imporant?

A

faiclitates the passage of increasing solid colonic contents and covers bacteria and particulate matter

29
Q

How are goblet cells stimautled

A

Ach in parasympatheric and enteric nervous system

30
Q

Which cells dominate the crypts?

A

goblet

31
Q

What about other cells?

A

no paneth cells

and enteroendocrine cells are rare

glycolayx has no digestive enzymes

32
Q

what is surface of microvilli covered with?

A

glycocalyx

33
Q

how do large bowel move food?

A

segmental contraction,

34
Q

what does the proximal colon do?

A

antipropuslive apttern dominate to retain chyme

35
Q

what does the transverese and descending colon do?

A

localised segemental contraction of circular muscle called hasustral contraction

causes back and forth mixing

36
Q

What increases molitiy of LI?

A

eating increases frequency

37
Q

what happens 1-3x a day in large powel?

A

mass movmement- resemble perisatlic wave

propels fibre that is usually indgestible through colon

38
Q

What does the parasym control?

A

ascending colon and most of transverse inervated by vagus

more distal innveravted by pelvic nerves

39
Q

what is inneravted the external sphincter?

A

somatic motor fibres in the pudendal nerves

40
Q

what is the defecation (poo) controlled by?

A

by saral spinal cord - both reflecx and voluntary actions

41
Q

What are the steps in defeaction?

A

reflex sudden distension of walls of rectum

pressure receptors send signals via myenteric plexus to intiate peristalic waves in desneind, sigmoid and rectum while internal anal sphinter inhbited

weak intrinstic

BRS (19 decks)

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