large intestine structure and function

Question 1

4 parts

Answer 1

acsending
transverse
descending
sigmoid

Question 2

muscuaris externa ofbowel

Answer 2

circular layer complete

longitudinal layer incomplete

Question 3

type of epitheliym

Answer 3

simple columnar

Question 4

rectum

Answer 4

straight muscular tube between sigmoid colon and anal canal

Question 5

colon function

Answer 5

actively transports sodium from lumen into blood –> osmotic absorption of water –> dehydration of chyme –> solid faecal pellets

Question 6

bacterial fermentation of undigested carbohydrate

Answer 6

short chain fatty acids
vitamin K
gas (flatus) - nitrogen, CO2, methane, hydrogen, hydrogen sulphide

Question 7

defaecation reflex

Answer 7

under parasympathetic control via pelvic splanchnic nerves

1. contraction rectum
2. relaxation of internal and contraction of external anal sphincters
3. inc peristaltic activity colon - inc pressure ext anal sphincter - relaxes under voluntary control - expulsion faeces

Question 8

symptoms assoc w constipation

Answer 8

headaches
nausea
loss of appetite
abdominal distenstion

Question 9

causes of diarrhoea

Answer 9

pathogenic bacteria
protozoans
viruses
toxins
food

Question 10

enterotoxigenic bacteria

Answer 10

produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells –> inc H20 secretion

water secretion swamps absorptive capacity of villus cells –> profuse watery diarrhoea

Question 11

treatment of secretory diarrhoea

Answer 11

sodium/glucose solution

drives water absorption –> rehydration
secretion still going –> wash away infection

oral rehydration therapy