Motility in the GI tract Flashcards
What are the three roles of motor activity in the GI tract?
Churns and mixes the food
Peristalsis moves the food in the right direction
Allows organs to act as reservoirs
Name the four functions of the small intestine
Digestion
Absorption
Secretion
Motility
What are the three functions of motility in the small intestine?
Mixing
Propulsion
Release into colon
What are the three methods of motility in the small intestine?
Rhythmic phasic contractions
Segmentation
Peristalsis
How does segmentation work?
Rings of circular muscle at intervals contract and then relax
How does peristalsis work?
Sequential contractions of rings of circular muscle followed by sequential relaxation
Behind the bolus of food
What is the migrating motor complex?
When in the fasting state, the migrating motor complex is the electrical activity that occurs every few hours
What is the role of the migrating motor complex?
To propel particles greater than 2mm in diameter from the stomach into the duodenum
Remove residual content from small intestine
Stop colonic bacteria moving backwards
What controls smooth muscle contraction?
Neurotransmitter (acetylcholine) Hormones Vasoactive intestinal peptide Stretch (myogenic) reflex Enteric nervous system
What are the two types of movement in the ileum?
Ileogastric reflex
Gastroileal reflex
What is the ileogastric reflex?
Ileal distension to decrease gastric motility
What is the gastroileal reflex?
Increased gastric activity causing increased ill motility
What does the ileocaecal sphincter separate?
The ileum and the colon
What regulates movement through the ileocaecal sphincter?
Pressure proximal and distal to the sphincter
What are taeniae coli?
3 muscular bands that run the length of the colon
What are the functions of the colon?
Absorb large quantities of fluid and electrolytes Absorb short chain fatty acids Storage/reservoir function Regulated release of faecal matter Secrete mucus and ions Home for beneficial bacteria
What are the two types of motility in the colon?
Colonic rhythmic phasic contractions
Giant migrating contractions
What controls motility in the colon?
Distension Food contents (e.g. fibre)
What are the four classifications of laxative?
Stimulant laxatives
Saline laxatives
Emollient laxatives
Bulk-forming laxatives
What kind of muscle makes up the anal sphincter?
Internal anal sphincter - smooth, involuntary
External anal sphincter - striated, voluntary
What are the stages to defaecation?
Faeces enter rectum and causes distension
Intrinsic defaecation reflex
Relaxation of internal sphincter
Conscious control of external sphincter
