Large Intestine Structure and Function

Question 1

Parts of large intestine

Answer 1

Ilemn
Ileocaecal valve
Caecum
Colon
Rectum

Question 2

Parts of colon

Answer 2

Ascending
Transverse
Descending
Sigmoid

Question 3

Mucosal epithelium

Answer 3

Simple columnar

Question 4

Lubrication for movement of faeces

Answer 4

Large, straight crypts lined with large number of goblet cells

Question 5

Rectum

Answer 5

Straight, muscular tube (between end of sigmoid colon and anal canal)

Question 6

Mucosa of rectum

Answer 6

Simple columnar epithelium

Question 7

Muscularis externa of rectum

Answer 7

Thick compared to other regions of alimentary canal

Question 8

Muscularis of anal canal campared to rectum

Answer 8

Thicker => contains internal anal sphincter

Question 9

External anal sphincter tissue type

Answer 9

Skeletal muscle

Question 10

Epithelium of anal canal

Answer 10

Simple columnar to stratified squamous

Question 11

Nutrient absorption role of colon

Answer 11

No important role in humans

Question 12

Function of colon

Answer 12

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

Question 13

Bacterial colonisation in colon as a result of

Answer 13

Long residence time - bacterial fermentation of undigested carbohydrate

Question 14

Colonic microflora resulting in

Answer 14

Short chain fatty acids (energy source in ruminants)
Vitamin K (blood clotting)
Gas (flatus) - nitrogen, CO2, hydrogen, methane and hydrogen sulphide

Question 15

Control of internal anal sphincter

Answer 15

Smooth muscle under automatic control

Question 16

Control of external anal sphincter

Answer 16

Skeletal muscle under voluntary control

Question 17

Urge to defaecate as a result of

Answer 17

Distension of rectal wall produced by mass movement of faecal material into rectum rsulting in mechanoreceptors triggering defaecation reflex

Question 18

Control of defaecation reflex

Answer 18

Parasympathetic control via pelvic splanchnic nerves

Question 19

Constipation resulting in

Answer 19

No absorption of toxins from faecal material following long periods of retention

Question 20

Symptoms associated with constipation

Answer 20

Headaches
Nausea
Loss of appetite
Abdominal distension

Question 21

Abdominal distension

Answer 21

When substances, such as gas or fluid, accumulate in the abdomen causing its expansion

Question 22

Causes of diarrhoea

Answer 22

Pathogenic bacteria
Protozoans
Viruses
Toxins
Food

Question 23

Enterotoxigenic bacteria

Answer 23

Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells
Increasing H2O secretion
Act by elevating intracellular second messengers:
cAMP
cGMP
calcium
H2O secretion swamps absorptive capacity of villus cells
Resulting in profuse watery diarrhoea

Question 24

Treatment of secretory diarrhoea (enterotexigenic bacteria)

Answer 24

Enterotoxins don’t damage villus cells
Give sodium/glucose solution
Drive water absorption => rehydration