What are the three phases of swallowing?
1. Oral phase: Voluntary
-Bolus: tongue ► pharynx
2. Pharyngeal phase: Involuntary
-Initiated by response to pressure
receptors in pharynx
-Directs bolus into esophagus via
relaxed upper esophageal sphincter (UES)
3. Esophageal phase: Involuntary
-Bolus from UES via peristalsis through
lower esophageal sphincter (LES) ► stomach
What is Barrett's esophagus? What is the cause?
A special type of GERD where columnar cells replace squamous cells in the mucosa of the esophagus.
Main cause is chronic acid exposure.
What is achalasia?
Failure of LES to relax, food in LES
What are diffuse esophageal spasms?
Uncoordinated esophageal contraction
What disease leads to Achalasia?
What happens physiologically to cause achalasia?
nerve degeneration (enteric nervous system)
- lack of NO synthase, VIP, etc
What is this called? What can trigger episodes?
Diffuse esophageal spasms
Hot or cold foods. Actual cause is not known
What is this called?
What is the Orad region of the stomach? What does it do?
The fundus and proximal body.
Recieves and stores food
What is the caudad region of the stomach? What does it do?
Distal body and antrum. Mixes and propels food.
What sets the maximal frequency of gastric contractility?
Frequency of slow waves
What are the components of gastric mixing?
How do hormones regulate the pyloric sphincter?
CCK, GIP, Secretin, Gastrin all constrict the pyloric sphincter.
What does neural regulation do to the pyloric sphincter.
Sympathetics --> Constriction
Parasympathetics --> constriction via acetylcholine
Relaxation via VIP
What is the postprandial period of segmentation?
Alternating contractions of circular smooth muscle.
What causes relaxation in front of the food bolus?
VIP and NO
What causes contraction behind the bolus?
ACh and Substance P
What does the migrating myoelectric complex do? What are the three phases?
Moves undigested material from stomach to the colon.
2. small disorganized contractions
3. Strong propagating contractions
What hormone is the migrating myoelectric complex associated with?
Motilin (a small intestinal hormone)
What are the three primary types of colonic motility?
2. Long-duration contractions
3. Mass movements
Describe haustration movement
Short-duration contractions (~ 8 sec stationary pressure waves)
Circular m. mixing contractions (not propulsive)
Describe the long-duration contractions in the colon.
(~ 20-60 sec)
Mixing contractions, may propagate short distances in either direction
Antipropulsive movements in proximal colon: retain chyme
Goal: slow movement through colon for absorption
Describe the mass movements of the colon
High-amplitude propagating contractions (high intensity)
Sweep length of colon (cecum to rectum)
High variability in colonic motility rates among individuals. (vs. small intestinal motility)
What is the long range reflex?
Gastric distension, gastrocolic reflex... stomach distention results in generalized increase in colonic motility.
What parasympathetics increase colonic motility, and where do they work?
Vagus n. via ENS:
Increased mixing contractions in proximal colon
vPelvic n.n. via ENS:
Increased contractions and propulsive movements in distal colon
What does distention of the rectum lead to?
Reflex relaxation of IAS, rectosphincteric reflex: VIP and NO
Refles constriction of EAS
What are the three events of defecation?
Voluntary relaxation of EAS
Contraction of abdominal m.m.
Relaxation of pelvic muscles