Flashcards in Large Intestine Deck (50)
Give 4 functions of gut microbes
Form secondary bile acids
Synthesise vitamin K
Degrade digested enzymes
Conversion of bilirubin to urobiligens
Metabolise undigested polysaccharides
Give 2 functions of mucus in large intestine
Provide adherent medium for faecal matter
Protection against acid abrasion and bacteria
What drives H2O movement in large intestine from lumen into blood?
Na movement, water follows by osmosis
Which proteins are involved in the movement of Na from lumen into blood in large intestine?
Electrogenic channels from lumen into cell
Na/K ATPase from cell into lateral space and then blood
What route does water take from lumen to blood in large intestine?
Transcellular due to tight junctions
What are the 2 types of motility in the large intestine?
Haustral contractions - mixing in ascending
Mass movements - propulsive in transverse and descending
What is the gastrocolic reflex?
When food is taken into mouth
Strength of mass movements increased
Response to gastrin and extrinsic autonomic nerves
Pushes the colonic contents into the rectum, triggering the defaecation reflex
What is the ileocaecal valve?
Valve between ileum and caecum
One way sphincter
Controls rate of chyme entry into large intestine
What is constipation?
Infrequent bowel movement <3 times per week
Incomplete evacuation of faces
Difficulty during defaecation - straining during 25% bowel movements
Type 1/2 Bristol stool chart
Name the 5 causes of constipation
Which people are most prone to constipation?
What are the 4 types of purgatives used to treat constipation?
What are methylcellulose and isphaghula husk?
Name 3 osmotic laxatives
Which purgative would you use before a procedure requiring a clean bowel?
Saline purgatives - magnesium sulphide or magnesium hydroxide
How does lactulose work?
Semi-synthetic disaccharide not broken down in SI
Colonic bacteria convert it to monosaccharides which are poorly absorbed in this region, they are fermented and then draw water into the lumen by osmosis
Act: within 1-3 days, Usage: useful against constipating effects of opioids, Side effects: abdominal cramping, gas, borborygmus and flatulence. Less common side effects, nausea and vomiting.
Excessively high dosage can cause explosive and uncontrollable diarrhoea. Tolerance can develop
Name 2 stimulant purgatives
Abuse of stimulant purgatives can cause...
Melanomas coli - dark pigment in colon, increased risk of colon cancer
Cathartic colon - weak and floppy colon
What are 5 causes of diarrhoea?
What are the 4 types of diarrhoea?
What is Loperamide and what is it used to treat?
It is an opioid drug, m-opioid receptors
Relatively selective to GI tract
Doesn't cross BBB
Used to treat diarrhoea by reducing motility. Increases tone and rhythmic contractions of colon, but diminishes propulsive activity
Pyloric, ileocaecal and anal sphincters are contracted
What are the constituents of oral rehydration therapy?
Isotonic or hypotonic solution
Describe the blood supply to the hindgut segment of large intestine
From IMA which branches into
Marginal artery provides anastamoses
Describe lymph drainage from GI tract
Lymph follows arteries
Drains to cisterna chyli
Drains to thoracic duct
Drains to subclavian artery
Which segment of large intestine is easiest to palpate and why?
Descending colon because faeces are compacted and solid at this point
What can surgeon use as reference point to help find appendix?
Follow taeniae coli down caecum
Appendix is at point where 3 bands join
Near ileocaecal junction
What is the classic pain pattern for appendicitis?
Starts in umbilical region, poorly localised. Referred pain
Moves to right iliac fossa and becomes sharp and extremely painful as peritoneum has become irritated
Which part of the stomach will you likely be able to see on a radiograph when patient is standing?
Fundus because it is often full of air
What is McBurney's point?
2/3rd distance from umbilicus to anterior superior iliac spine (ASIS). Point that used to be used for appendectomy surgery