Physiology Of Defeaction Flashcards
What are the main functions of the colon?
Absorption of water and electrolytes
Production of vitamins
Excretion of waste
Anatomy of the colon from the caecum to the anus…
Caecum (with appendix) Ascending colon (Hepatic flecture) Transverse colon (Splenic flecture) Descending colon Sigmoid colon Rectum Anus
What is a colonoscopy?
A test to check inside your bowels. This test can help find what’s causing your bowel symptoms. A long, thin, flexible tube with a small camera inside it is passed into your bottom. You’ll be given a laxative so your bowels are empty for the test.
Layers of the colonic wall:
Lumen Mucosa Muscularis mucosae Submucosa Muscularis propia Subserosa Serosa
Taenia colon =
Omental appendices =
three separate longitudinal ribbons of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons
= fatty tags
Histology of the colon =
Columnar epithelium
Goblet cells - mucous for lubrication
How is water absorbed by the colon? Overview
Water is absorbed by osmosis
Na+ are actively transported into the colon epithelium cells - decrease osmolarity so water moves in by osmosis
How does the colon produce vitamins?
Colonic micro biome = breakdown indigestible food and produce vitamins as they do - mostly K and B
Nerve supply to the colon
Intrinsic = in organ = meissners and Auerbach plexus
Extrinsic = parasympathetic - vagus - increase rest and digest
Sympathetic = slow bowel
What is the gastro-colic reflex?
Stomach stretching and food in the jejunum leads to mass movement of the colon
This is why you may need a poo just after you eat
Epithelium of the anus changes…
Epithelium changes from columnar to stratified squamous epithelium at dentate line (same as skin)
Circulation also changes from portal circulation to the liver
To systemic circulation
What are the sphincters of the anus?
When rectum Empty =
When full =
When emptying =
Internal and external anal sphincter
IAS = rectum muscle
EAS = pelvic floor (voluntary)
Empty = both contracted
Relaxation of only the interval anal sphincter
Relaxation of both
How do we know we need to poo?
Completed?
Rectum fills, relaxation of internal sphincter
External sphincter relaxes,
puborectalis relaxes (pelvic floor muscle that maintains the angle between the rectum and anus and hence stops fences passing through)
- becomes straight loss of ANORECTAL angle
Rectum contacts
Valsalva manoeuvre (breath put and tense) - pressure
How to improve your anorectal angle and hence help the passing of faeces
If your puborectalis muscle is not functioning properly
Squatting with feet up and leaning forward can help decrease angle and hence empty the rectum
- mostly effect women after menopause and pregnancy
What is diarrhoea and its most common causes?
Lose watery - usually frequent stools
Infection of colon - cholera
IBD
Reduced rectal capacity
Cant control motion - pelvic floor disorders
