Constipation and IBS - 209

Question 1

What is the role of the myenteric plexus?

Answer 1

Provides motor innervation to both layers (longitudinal and circular muscle) of the GI tract, with sympathetic and parasympathetic input

Question 2

What is the role of the submucous plexus?

Answer 2

Provides motor innervation to the muscularis mucosae under parasympathetic input only

Question 3

What is Hirschsprung’s disease?

Answer 3

Absent peristalsis due to an aganglionic large bowel

Question 4

Name the stimulatory transmitters of the colon

Answer 4

ACh and Substance P

Question 5

Name the inhibitory transmitters of the colon

Answer 5

VIP and NO

Question 6

Describe the gastro-ileal reflex

Answer 6

Caecal and IVC relaxation after food leaves the stomach. It influences normal colonic function

Question 7

What is the innervation of the internal anal sphincter?

Answer 7

Autonomic, SNS is excitatory and PNS is inhibitory

Question 8

What nerve supplies the external anal sphincter?

Answer 8

Pudendal nerve.

Question 9

What happens during defecation following the voluntary decision and straining?

Answer 9

• Decrease in pelvic floor tone and sphicters
• Decrease in anorectal angle
• Increased tone in abdominal muscles
• Passage of stool!

Question 10

What is obstructed defecation syndrome characterised by? What can cause this?

Answer 10

Straining, laxative dependency, incomplete evacuation, pain.
Rectocele -> chronic straining produces stretching and redundancy of distal rectum

Question 11

Give an example of a neurological and endocrine disorder than can cause constipation

Answer 11

Neuro: Parkinson’s, MS
Endo: Diabetes, hypothyroidism

Question 12

How do bulk-forming laxatives work?

Answer 12

They retain fluid within the stool, increasing faecal mass and stimulating peristalsis

Question 13

How do osmotic laxatives work?

Answer 13

Increase fluid in the large bowel, produce distension and stimulate peristalsis