Motility in the GI tract Flashcards
What motor activity does the GI tract perform and its functions?
Segmental contractions (mixing) Peristaltic contractions Tonic contraction (sphincters)
What is the function of the small intestine?
Location for almost all digestion and absorption
Secretion of Chyme into the colon
What types of motility are in the small intestine during the fed state?
Segmentation
Peristalsis
(these types are rhythmic phasic contractions (RPCs))
How does segmentation work?
Rings of contractile muscle at intervals contract then relax pushing bolus around.
Used for mixing mainly
How does peristalsis work?
Sequential contractions of rings of circular muscle followed by sequential relaxation.
Combination of activity between muscular layers, with sequential activity in each of them.
Propels chyme along
What regulates peristalsis during the fasting state?
Migratory motor complex (MMC).
What is the MMC?
Large sweeps of electrical activity causing contraction down the small intestine.
What is the purpose of the MMC?
Propel particles from the stomach into the duodenum
Clear small intestine of its residual content (undigested food)
Stops colonic bacteria from entering into the terminal ileum
What types of reflex are present in the ileum?
Ileogastric reflex
Gastroileal reflex
Mediated via the ENS
What is the Ileocaecal Sphincter?
Separates the ileum from the colon.
Operate based on sensory neurones detecting pressure changes via the ENS.
What is the Colon?
Last 4ft of the GIT
Surface area only 1/30th of the small intestine.
No villi
What are the parts of the colon?
Ascending Transverse Descending Sigmoid Rectum
What are Taeniae Coli?
Longitudinal muscle layers thickened to form 3 muscular bands which run the length of the colon
What is the function of the Colon?
Absorb large quantities of fluid and electrolytes thus converting liquid content to solid.
Metabolises fibres into short chain fatty acid (glutarate) to be absorbed. (caused by microbiota fermenting the fibres into the SCFA)
Storage and reservoir function
Regulate release of faecal material
Provides environment for comensal bacteria which synthesise vitamins
Secretes mucous and ions.
What are the functions of the proximal colon?
site of absorption and bacterial fermentation