Lecture 6 : Intestinal Motility

Question 1

What is meant by segmentation in the intestines

Answer 1

Where rings og circular muscle at intervals contract then relax, and adjacent rings contract and relax, in order to mix chyme

Question 2

Peristalsis def

Answer 2

Sequential contractions of rings of circular muscle followed by sequential relaxation, propelling chyme along/

Question 3

What is the migrating motor complex

Answer 3

Every 90 mins, pattern of cyclical wave-like contractions in stomach and small intestine occur WHILE FASTING.

1. Period of quiet
2. Increasing action-potentials / contractility
3. Peak electrical and mechanical activity, lasts a couple mins
4. Declining activity merging into next quiet period

Its role :
- Clears small intestines of residual content
- Stops colonic bacteria from migrating to terminal ileum, vulnerable because it is at the end of the small intestine and not used to colon bacteria

Terminates when eating.

Question 4

The Colon

Answer 4

No Villi

Absorbs large quantities of food and electrolytes

Absorbs short chain fatty acids from carbohydrate fermentation

Releaeses faecal material

Store / reservoir

Provides environment for synthesis of vitamin B complexes and beneficial bacteria

Secretes mucus and ions like K+, Cl- and HCO3-

Question 5

Colon Motility

Answer 5

2 main types of contractions, rhythmic phasic contractions, and giant migrating contractions

Rhythmic Phasic (Haustral) :
- Increases contact of faeces to mucosal wall, so increased absorption of water electrolytes and vitamins
- Causes ‘pouches’ of food called haustra

Giant Migrating (peristalsis) :
- Alternating waves of contraction and relaxation
- Propulsion
- During fasting and postprandial states
- Occurs randomly 2-10 times a day
- Clears colon of remaining food, prevents bacterial overgrowth

Question 6

Hirschprung Disease

Answer 6

Question 7

Defecation reflex

Answer 7

Question 8

Colon motility regulation

Answer 8