Gastrointestinal Motility

Question 1

How are smooth muscle fibers arranged?

Answer 1

In inner circular and outer longitudinal layers

Question 2

What are the fundamental patterns of motility conducted by the digestive tube include?

Answer 2

Peristalsis
Mixing (segmentation)
Migrating motor complex

Question 3

What is peristalsis?

Answer 3

A reflex response that is initiated by stretch of the gut wall by the contents of the lumen
The stretch initiates a strong constrictor wave behind bolus and an area of relaxation in front of it

Question 4

What does the stretch stimulate?

Answer 4

The release of serotonin that activates sensory neurons that in turn activate cholinergic fibers that pass in retrograde direction to cause smooth muscle contraction behind the bolus and anterograde direction to cause relaxation in front of the bolus

Question 5

What is mixing (segmentation)?

Answer 5

Mixing contractions are seen especially in small intestine in the form of constrictor rings that appear at regular intervals then disappear to reappear at new points
This helps to mix food with the digestive enzymes and also helps absorption

Question 6

What is migrating motor complex?

Answer 6

A distinct pattern of electromechanical activity observed in gastrointestinal smooth muscle during fasting (the periods between meals)