Physiology- Basics

Question 1

What are the 4 layers of the GIT? (deep to superficial)

Answer 1

Mucosa, Submucosa, Muscularis externa, Serosa

Question 2

Which phase of deglutition is voluntary?

Answer 2

Oral phase (pharyngeal and esophageal are involuntary)

Question 3

Rugae are present in which part of the GIT?

Answer 3

Stomach

Question 4

What is receptive relaxation? Why does it occur? Is it essential to digestion?

Answer 4

Stomach distends in response to volume increases in order to control pressure. Not essential for digestion (ie Bariatric surgery)

Question 5

What 3 things increase surface area in the small intestine? Which one increases it most?

Answer 5

Folds and projections: Plicae circularis, villi and microvilli (increases 300x)

Question 6

Crypts of Lieberkuhn are present in which part of the GIT?

Answer 6

AKA Intestinal Crypts found in villi

Question 7

T or F? The large intestine has many villi and crypts.

Answer 7

FALSE- no villi or crypts

Question 8

What part of the GIT contains a large population of microflora?

Answer 8

Large Intestine (this means it is not sterile)

Question 9

What 2 plexuses make up the enteric nervous system (ENS)? Where are they located? What are they responsible for?

Answer 9

1. Myenteric (Auerbach’s) Plexus: Between outer longitudinal and inner circular smooth muscle layers from esophagus to rectum; muscle contraction
2. Submucosal (Meissener’s) Plexus: between inner layer of circular smooth muscle and submucosa, predominantly in intestines; secretion and absorption

Question 10

What does the ENS do?

Answer 10

Coordinates digestion, secretion, and motility to optimize nutrient absorption. Its activity is modified by information from the CNS and from local chemical and mechanical sensors.

Question 11

What are the pacemaker cells of the GIT (responsible for generating electrical activity (BER))? Where are they located?

Answer 11

Interstitial Cells of Cajal (ICC) in the myenteric plexus.

Question 12

What are the 4 motor patterns in the GIT?

Answer 12

1. Peristalsis
2. Segmentation
3. The migratory motor complex (MMC)
4. The postprandial motor patterns

Question 13

What is peristalsis? Describe the mechanism.

Answer 13

Peristalsis consists of coordinated contraction and relaxation of circular and longitudinal muscles to move food bolus.
Contraction of longitudinal muscles (dilation) in the receiving segment (inhibition of circular muscle).
Contraction of circular muscles upstream and relaxation in the receiving segment.

Question 14

What determines the frequency of peristaltic contractions?

Answer 14

The BER.

Question 15

What is segmentation? Describe the mechanism. What determines the frequency of segmentation?

Answer 15

Segmentation results from activation of peristaltic reflex in several gut segments, triggering opposing peristaltic reflex contractions in adjacent segments.
The BER.