Colonic Function and Motility

Question 1

Where does the superior hypogastric plexus come from?

Answer 1

Nerves from L1-L2

Question 2

Where does the inferior hypogastric plexus come from?

Answer 2

S2-4

Question 3

how are the muscles organised in the bowel wall?

Answer 3

Circular and Longitudinal Muscle

Question 4

What part of the ANS does the Myenteric plexus of Auerbach supply?

Answer 4

SNS and PSNS

Motor to L&C muscle

Secretomotor to mucosa

Question 5

What part of the ANS does the sub-mucosal plexus of Meissner supply?

Answer 5

PSNS only

Motor to muscularis mucosae, mucosal receptors

Question 6

What is the condition where there are no ganglia in the myenteric plexus? and what is the consequence of this?

Answer 6

Hirschprung’s

Absent Peristalsis

Question 7

What does the proximal colon include?

Answer 7

The ascending and transverse parts of the colon.

Question 8

What does the distal part of the colon include?

Answer 8

The descending and recto-sigmoid colon

Question 9

What happens in the proximal colon?

Answer 9

Fluid/electrolyte and bacterial fermentation

Most contraction occurs here: Non-propulsive segmentation and Mass peristalsis

Question 10

What is involved in non-propulsive segmentation?

Answer 10

Slow wave activity → Circular muscle contraction (appearance of segments/haustra)

For mixing and absorption of contents

Question 11

What is involved with mass peristalsis?

Answer 11

Simultaneous smooth muscle contraction, contents propelled distally

Question 12

What is the function of the distal colon?

Answer 12

Reservoir function - non-propulsive segmentation

Question 13

Name two stimulators of colonic motility

Answer 13

Acetycholine and Substance P

Question 14

Name two inhibitors of colonic motility.

Answer 14

Vasoactive Intestinal Peptide (VIP)

Nitrous Oxide (NO)

Question 15

What is the outer border of circular muscle responsible for?

Answer 15

Myenteric potential oscillations → Flatus

Question 16

What is the inner border of circular muscle responsible for?

Answer 16

High amplitude, low frequency waves → defaecation

Question 17

Describe the Gastro-ileal reflex

Answer 17

Caecal and ileo-caecal valve relaxation after food leaves the stomach → increased passage of chyme through ICV

Question 18

Delayed Gastrocolic reflex

Answer 18

Gastric distension **→ **desire to defaecate

(Gastrin)

Question 19

What type of muscle is the internal sphincter?

Answer 19

Smooth muscle

Question 20

What type of muscle is the external sphincter? Name the different portions.

Answer 20

Striated muscle

Deep portion

Superficial portion

Subcutaneous portion

Question 21

how is the internal sphincter controlled?

Answer 21

Involuntary

Sympathetic → excitation

(RAIR: rectal distension →) Parasympathetic → relaxation → defaecation

Question 22

What nerve innervates the striated muscle of the external sphincter?

Answer 22

Pudendal nerve

Question 23

What does rectal distension do to the external sphincter?

Answer 23

Increase the tonic contraction

Question 24

What happens during straining for defaecation?

Answer 24

Reflex inhibition → decrease anorectal angle

Question 25

What happens electrically post defaecation?

Answer 25

There is a burst of electrical activity → restore normal tonicity

Question 26

What is involved in the recto-rectal reflex?

Answer 26

Proximal bowel contracts, and distally relaxes

Question 27

What muscular changes occur in straining?

Answer 27

Decreased tone in pelvic floor/sphincters Decreased ano-rectal angle Increased tone in abdominal musculature

Question 28

What is involved in the rectoanal inhibitory reflex?

Answer 28

Rectal distension → Internal anal sphincter relaxation

Question 29

What is dyssynergic defaecation?

Answer 29

Rectal Hyposensitivity Abnormal rectal compliance Paradoxical anal sphincter contraction Poor abdominal-rectal propulsive force

Question 30

What does mamometry of the anal canal measaure?

Answer 30

Pressure Resting pressure - internal sphincter Maximum squeeze - external sphincter

Question 31

What would the mamometry show for someone with incontinence?

Answer 31

Lower baseline pressure No increase in anus pressure with increased rectal pressure Cannot increase pressure with squeeze

Question 32

What is a rectocoele?

Answer 32

Protrusion of anterior rectal wall

Question 33

What is rectal intussusception?

Answer 33

May be preliminary to prolapse. Feel rectal fullness - tenesmus

Question 34

What is anismus?

Answer 34

Damage to nerves supplying rectum (i.e. pudendal) Failure to relax pelvic floor muscles

Question 35

What does a delayed transit and normal proctogram suggest? What are the treatment options?

Answer 35

Idiopathic Slow Transit Constipation Colectomy + Ileorectal Anastamoses, ACE (enema) , Sacral Nerve Stimulation

Question 36

What does a normal Transit but Abnormal Proctogram indicate? And what is the treatment?

Answer 36

Intussusception or Prolapse Resection rectopexy, Repair of rectocoele, ACE