Colonic Function

Question 1

Colonic-Rectal motor function

Answer 1

Vagus nerve proximal to tvs
Pelvic nerve below
SUperior and inf mesenteric ganglia, hypogastric ganglia for rectum and anus
Pudendal nerves for EAS

Contain bacteria that digest cellulose
Very slow and irregular BER with no MMC

Question 2

Reflexes

Answer 2

Distension of ielum dec sphincter tone

Distension of colon increases tone to prevent reflux

Question 3

Haustrations and propulsions

Answer 3

Haus - kneading movement

Propulsion - mass movements 1-3 times per day may be tirggered by gastrocolic reflex …may be associated with post-prandial pain (IBS)

Question 4

Neural and hormonal regulation

Answer 4

Gastrin inc and NE dec rate of BER

Pain fear and anxiety will dec motility and may cause constipiation or diarrhea

Question 5

Colonic secretions

Answer 5

Primarily mucus and high in K…K/Na exchange stimulated by aldosterone

Regulation of secretions primarily local, SNS dec with PNS inc, aldosterone, and some cAMP transport

Question 6

Rate of transit effect

Answer 6

If moved rapidly, limits reabsorption

Na+ reabsorption creates gradient for water reabsorpition

Question 7

Water resorption

Answer 7

Most in small intestine

Similar mechs with osmotic gradeint established by Na transport

Question 8

Defacation

Answer 8

IAS - relaxed by ENS release of NO and VIP

EAS - striated fro mpudendal nerve
…also by distensiojn and coughing

Angle prevent fecal escape

Passing of gas is associated with relaxation of EAS while maintaing puborectalis contraction

Rectum normally empty and thus retrograde predominates when sphincters are closed

Question 9

Dysfunctions of colon

Answer 9

Diarrhea from shortened transit times, enhanced gastrocolic reflex, inc propulsive contraction in the colon

Constipation from inc transit time

Megacolon - constricted segment of colon

ANal incontinendce could be from indigestbiel fat for neural/musc problems