Swallowing, Gastric Emptying, Intestinal Motility

Question 1

What are the three phases of swallowing?

Describe each

Answer 1

1. Oral phase: Voluntary
   
   • Bolus: tongue ► pharynx
2. Pharyngeal phase: Involuntary
   
   • Initiated by response to pressurereceptors in pharynx
   -Directs bolus into esophagus viarelaxed upper esophageal sphincter (UES)
3. Esophageal phase: Involuntary
   
   • Bolus from UES via peristalsis through
   lower esophageal sphincter (LES) ► stomach

Question 2

What is Barrett’s esophagus? What is the cause?

Answer 2

A special type of GERD where columnar cells replace squamous cells in the mucosa of the esophagus.

Main cause is chronic acid exposure.

Question 3

What is achalasia?

Answer 3

Failure of LES to relax, food in LES

Question 4

What are diffuse esophageal spasms?

Answer 4

Uncoordinated esophageal contraction

Question 5

What disease leads to Achalasia?

Answer 5

Chagas disease

Question 6

What happens physiologically to cause achalasia?

Answer 6

nerve degeneration (enteric nervous system)

 - lack of NO synthase, VIP, etc

Question 7

What is this called? What can trigger episodes?

Answer 7

Diffuse esophageal spasms

Hot or cold foods. Actual cause is not known

Question 8

What is this called?

Answer 8

Achalasia

Question 9

What is the Orad region of the stomach? What does it do?

Answer 9

The fundus and proximal body.

Recieves and stores food

Question 10

What is the caudad region of the stomach? What does it do?

Answer 10

Distal body and antrum. Mixes and propels food.

Question 11

What sets the maximal frequency of gastric contractility?

Answer 11

Frequency of slow waves

Question 12

What are the components of gastric mixing?

Answer 12

Propulsion

Grinding

Retropulsion

Trituration

Question 13

How do hormones regulate the pyloric sphincter?

Answer 13

CCK, GIP, Secretin, Gastrin all constrict the pyloric sphincter.

Question 14

What does neural regulation do to the pyloric sphincter.

Answer 14

Sympathetics –> Constriction

Parasympathetics –> constriction via acetylcholine

Relaxation via VIP

Question 15

What is the postprandial period of segmentation?

Answer 15

Alternating contractions of circular smooth muscle.

Question 16

What causes relaxation in front of the food bolus?

Answer 16

VIP and NO

Question 17

What causes contraction behind the bolus?

Answer 17

ACh and Substance P

Question 18

What does the migrating myoelectric complex do? What are the three phases?

Answer 18

Moves undigested material from stomach to the colon.

1. Quiescence
2. small disorganized contractions
3. Strong propagating contractions

Question 19

What hormone is the migrating myoelectric complex associated with?

Answer 19

Motilin (a small intestinal hormone)

Question 20

What are the three primary types of colonic motility?

Answer 20

1. haustration
2. Long-duration contractions
3. Mass movements

Question 21

Describe haustration movement

Answer 21

Short-duration contractions (~ 8 sec stationary pressure waves)

Circular m. mixing contractions (not propulsive)

Question 22

Describe the long-duration contractions in the colon.

Answer 22

(~ 20-60 sec)

Taeniae coli

Mixing contractions, may propagate short distances in either direction

Antipropulsive movements in proximal colon: retain chyme

Goal: slow movement through colon for absorption

Question 23

Describe the mass movements of the colon

Answer 23

High-amplitude propagating contractions (high intensity)

Sweep length of colon (cecum to rectum)

1-3/day (1-10/day)

High variability in colonic motility rates among individuals. (vs. small intestinal motility)

Question 24

What is the long range reflex?

Answer 24

Gastric distension, gastrocolic reflex… stomach distention results in generalized increase in colonic motility.

Question 25

What parasympathetics increase colonic motility, and where do they work?

Answer 25

Vagus n. via ENS:

Increased mixing contractions in proximal colon

vPelvic n.n. via ENS:

Increased contractions and propulsive movements in distal colon

Question 26

What does distention of the rectum lead to?

Answer 26

Reflex relaxation of IAS, rectosphincteric reflex: VIP and NO

Refles constriction of EAS

Question 27

What are the three events of defecation?

Answer 27

Voluntary relaxation of EAS

Contraction of abdominal m.m.

Relaxation of pelvic muscles

Question 28

Identify

Answer 28

This course