Large Intestine Structure and Function

Question 1

Name the four parts of the large intestine

Answer 1

Ascending, Transverse, Descending and Sigmoid colon

Question 2

Define Teniae Coli

Answer 2

Three seperate longituidinal ribbons of smooth muslc on the outside of the colon. They contract to produce the hausta.

Question 3

Composition of colon epithelia of the large intestine

Answer 3

The large intestine is composed of simple flat columnar epithelia

Question 4

Histological Features of the Large intestine

Answer 4

Large straight crypts lined with goblet cells

Question 5

Function of Goblets cells in the large intestine

Answer 5

Lubrication for movement of faeces

Question 6

Describe the composition of the rectum

Answer 6

Straight muscular tube composed of simple columnar epithelia. Muscularis externa thicker composed to other regions

Question 7

Describe the Anal Canal

Answer 7

The Muscularis extrena is thicker than the rectum and forms the internal anal sphincter (involuntary), and skeletal muscle forms the external anal sphincter.

The epithelial is transitions from simple columnar to stratified squamous

Question 8

What is the illeocecal valve

Answer 8

Seperates the illeum and the cecum.

Question 9

Function of the Colon

Answer 9

Transport of Na+ from the lumen, into blood, reabsorbs water, dehydrating chyme fro extertion.

Bacterial Colonosation allows undigested carbohydrates to be broken down. Cellulase/Cellulose

Question 10

Mechanism of Defecation

Answer 10

Mass Movement Contraction (intense contraction) moves chyme from the colon to the rectum.

Distension of the rectal wall is sensed by mechanorecptors which triggers the defecation reflex

Question 11

What is the defecation reflex

Answer 11

The defecation reflex causes the internal sphincter to relax and the external sphincter to contract.

The voluntary choice is then either to defecate or wait and anal canal muscle will push the faeces back.

Question 12

Is the defecation reflex under sympathetic or parasympathetic control

Answer 12

Parasympathetic via pelvic splanchic nerves.

There is no sympathetic influence.

Question 13

Symptoms associated with constipation

Answer 13

Headaches
Nausea
Loss of appetite
Abdominal distension

Question 14

Cause of diarrhoea

Answer 14

pathogenic bacteria
protozoans
viruses
toxins
food
stress

Question 15

Mechanism of Enterotoxigenic Bacteria on the colon

Answer 15

Produces protein enterotoxins which turn on intestinal chloride secretion from crypt cells by elevating intracelluar messengers. cAMP, cGMP, and calcium

This increases water secretion - profuse watery diarrhoea

Water secretion > water absorption by villi

Question 16

How to combat enterotoxigneic bacteria

Answer 16

Gives Na/glusice solution as this drives water absiroption