gastroenterology - large bowel

Question 1

What does the large bowel consist of?

Answer 1

colon (ascending, tranverse and descending)

caecum

appendix

recturn

anal canal

Question 2

What is the caecum?

Answer 2

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

Question 3

what types of organisms have larger caecum?

Answer 3

herbivors

Question 4

what is the appendix?

Answer 4

thing extention of caecum , not relevant in humans

Question 5

what are main function of large bowel?

Answer 5

reabsoprtion of electrolyes and water

elimination of undgiested food and waste

Question 6

what are the 4 types of colon?

Answer 6

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

Question 7

What is the blood supply to colon?

Answer 7

proximal transverse - middle colic artery

distal 3rd transverse colon - inferior mesenteric artery

regions between the 2 senstive to ischemia

Question 8

what is the perotenium?

Answer 8

layer surroding colon

Question 9

Where are nodules of lymoid tissues common?

Answer 9

walls of distal small intestine - pyere’s patch

large intestine - solitary nodules

Question 10

what is the strucutre of the peritoneum?

Answer 10

fatty tags - appendices epiploicae

and muscle coat with 3 bands (taeniae coli)

Question 11

What is function of taenia coli?

Answer 11

large intestine motlity

Question 12

Why do large intestine have their appearance as it is?

Answer 12

taenia coli are shorter

so forms pouched ovoid segments called hasutra

Question 13

where does more abosrption take place in colon?

Answer 13

proxmial colon

Question 14

how do large intestines absorb water?

Answer 14

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

water follows by osmosis

K+ moves passively into lumen

Question 15

What is the rectum strucutre?

Answer 15

dilated distal portion of alimentary canal

Question 16

how is rectum distringushed from colon?

Answer 16

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

Question 17

what muscles is the anal canal surronded by?

Answer 17

internal (circular muslce)

external (striated muscle)

anal sphincters

Question 18

Answer 18

Question 19

What 4 layers in the large bowel made from?

Answer 19

mucosa, submucosa, muscularis, serosa

Question 20

which layer habours myetenric plexus?

Answer 20

serosa

Question 21

which 2 layers have glands?

Answer 21

mucosa and submucosa

Question 22

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

Answer 22

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

a lot of crypts - stem cells

Question 23

Why does mucosa appear smooth?

Answer 23

as have no villi

Question 24

what is important about strucutre of entrocyes?

Answer 24

have short irregular microvilli - concerned resportion of salt

Question 25

what has more goblet cells large or small bowel?

Answer 25

large

Question 26

Where are they more prevelant in large bowel?

Answer 26

in crypts than along the surface and increase distally towards rectum

Question 27

what is charactistic of goblet cell?

Answer 27

apical ends are packed with mucus filled secretions granules awaiting release

Question 28

Why is mucus imporant?

Answer 28

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

Question 29

How are goblet cells stimautled

Answer 29

Ach in parasympatheric and enteric nervous system

Question 30

Which cells dominate the crypts?

Answer 30

goblet

Question 31

What about other cells?

Answer 31

no paneth cells and enteroendocrine cells are rare glycolayx has no digestive enzymes

Question 32

what is surface of microvilli covered with?

Answer 32

glycocalyx

Question 33

how do large bowel move food?

Answer 33

segmental contraction,

Question 34

what does the proximal colon do?

Answer 34

antipropuslive apttern dominate to retain chyme

Question 35

what does the transverese and descending colon do?

Answer 35

localised segemental contraction of circular muscle called hasustral contraction causes back and forth mixing

Question 36

What increases molitiy of LI?

Answer 36

eating increases frequency

Question 37

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

Answer 37

mass movmement- resemble perisatlic wave propels fibre that is usually indgestible through colon

Question 38

What does the parasym control?

Answer 38

ascending colon and most of transverse inervated by vagus more distal innveravted by pelvic nerves

Question 39

what is inneravted the external sphincter?

Answer 39

somatic motor fibres in the pudendal nerves

Question 40

what is the defecation (poo) controlled by?

Answer 40

by saral spinal cord - both reflecx and voluntary actions

Question 41

What are the steps in defeaction?

Answer 41

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