L6*-Intestines motility & Control-Ibruhim Flashcards
(12 cards)
Define Propulsion
moving food to correct sites for digestion, absorption and make way for further material emptied from stomach.
Define Chyme
semi-liquid substance from stomach with secretions of pancreas, liver, intestines with a mix of partially digested food.
Describe the steps of intestinal motility from fed state to the fasted state.
- Segmentation - rings of circular muscle at intervals contract and then relax. Then adjacent rings contract and relax.
Overall result : mixing mainly
Fed state - Peristalsis - sequential contractions of rings of circular muscle followed by sequential relaxation. Combination of activity between muscular layers, with sequential activity in each of them.
Overall result : propels chyme along.
Fed state - In the fasting state the small bowel is relatively dormant(slowed down or reduced). But it does exhibit synchronised, rhythmic changes in both electrical and motor activity which is termed the migrating motor complex (MMC).
What are the 4 phases of MMC? and their function overall ?
- MMCs in humans occur at intervals of 90 to 120 minutes and consist of four distinct phases:
- A prolonged quiescent period.
- Period of increasing action-potential frequency and contractility.
- Period of peak electrical and mechanical activity that lasts a few minutes.
- Period of declining activity that merges into the next quiescent period.
FUNCTION - The role of the MMC is to propel particles greater than 2 mm in diameter from the stomach into the duodenum.
Define Colon, how much of the colon does make up the GIT and what does it not have? Name 6 functions of the colon.
-Colon is made up of the last 4ft of the GIT. It has no villi.
6 FUCNTIONS :-
1. To absorb large quantities of fluid and electrolytes
2. Absorb short chain fatty acids (product of carbohydrate fermentation)
3. Regulate release of faecal material
4. Store/reservoir
5. Provides environment for synthesis of vitamins B complex and K-beneficial bacteria
6. Secretes mucus and ions (K+, Cl-, HCO3-)
What are the 2 sections of the colon ?
- Proximal colon - site of absorption and bacterial fermentation.
- Distal colon - reservoir/storage function
What are the 2 types of colon motility?
-Rhythmic phasic contractions
-Giant migrating contractions
Explain -Rhythmic phasic contractions-colon motility 1 type
-Also known as Haustral contractions
-👆ses contact of faeces to mucosal wall = 👆sed absorption of water, electrolytes, vitamins.
- The contractions vary widely in amplitude and duration.
- The contraction causes (pouches) known as Haustra.
Explain - Giant migrating contractions-colon motility 2 type
-also known as mass movement peristalsis.
- alternating waves of contraction and relaxation gives large amplitude over long distances = propulsion.
- occurs during both fasting and postprandial states.
-Occurs randomly about 2 to 10 times a day
What is Hirschsprung disease ?
also known as Aganglionic megacolon.
The aganglionic(no ganglion so no stimulation), aperistaltic bowel segment effectively prevents the propulsion of the faecal stream, resulting in in megacolon) above the point where the nerves are missing and hypertrophy of the normal proximal colon.
What type of reflex is needed from the brain to regulate the colon motility?
long range intestinal reflexes
AND
gastrocolic reflex
Define Defecation reflex
- Faeces in sigmoid colon and rectum initiate stretch reflexes
- Stretch receptors are activated- parasympathetic nervous system-motor fibres
- Acetylcholine is released→ contraction of sigmoid colon and rectum
- Internal anal sphincter (made up of an involuntary smooth muscle) are activated by PNS →relaxation of the muscle
- External anal sphincter (made up of voluntary smooth muscle) are innervated by somatic
nervous system - CNS send signal to external anal sphincter to relax → faeces out
