GI Motility

Question 1

Describe the basic structure of a cell lining the GI tract.

Answer 1

. Mucosa (closest to lumen, microvilli) and submucosa
. Myenteric plexus (outer) and submucosal plexus (inner)
. Outer longitudinal muscle, inner circular muscle

Question 2

Which cells are responsible for basal electrical rhythm in controlling gut motility?

Answer 2

Pacemaker cells (Interstitial Cells of Cajal, ICCs)

Question 3

Name 2 GI tract motility stimulatory hormones (stimulate contraction)

Answer 3

Gastrin (antrum) and motilin (from small intestine)

Question 4

Name 3 inhibitory GI tract motility hormones (stimulate relaxation)

Answer 4

Gastrin (from proximal stomach), secretin, CCK

Question 5

Rate at which gastric contents passes into duodenum depends on which two main factors?

Answer 5

GI motility and meal composition

Question 6

Which types of food pass through the stomach quicker/slower?

Answer 6

Carbs pass quickest, then protein, then fat (Action of CCK quite slow)

Question 7

What are the two types of contraction in the small intestine?

Answer 7

Segmenting and peristaltic

Question 8

What is segmenting contraction?

Answer 8

(Inner layer) circular muscle, moves chyme back and forth to increase exposure to mucosal surfaces

Question 9

What is peristaltic contraction?

Answer 9

(Outer layer) longitudinal muscle propels food along GI tract

Question 10

How long does it take for food to reach the terminal ileum?

Answer 10

Around 12 hours

Question 11

What kind of contractions occur in the terminal ileum

Answer 11

Haustral contractions (kneading action, like segmenting contraction but less frequent)

Question 12

What is the gastro-colic reflex?

Answer 12

Food in stomach stimulates defecation

Question 13

Gastrin has different effects on GI motility depending on where it acts. What are these different effects?

Answer 13

Gastrin in proximal stomach= relaxation 9allows food into stomach)
Gastrin in antrum= contraction (pushes food out of stomach)