GI Swallowing and Gastric Motility Flashcards
Swallowing
Initiated voluntarily in the mouth
Then under involuntary control by the swallowing center in the medulla
3 Phases:
Oral Phase
Pharyngeal Phase
Esophageal Phase
Oral Phase of Swallowing
(1 of 3)
- Voluntary Control
- Tongus pushes bolus against soft palette
- Triggers the swallow reflex
Pharyngeal Phase of Swallowing
(2 of 3)
- Under involuntary control
- Propulsion of food bolus from mouth through pharynx to esophagus
- Soft pharynx moves upwards to close off the nasopharynx
- Epiglottis moves downward to cover the trachea
- During this process, respiration is temp. suppressed
Pharynx is the common opening for the digestive tract and respiratory tract
Esophageal Phase of Swallowing
(3 of 3)
- Involuntary control
- Closure of UES to prevent reflux
- Bolus is propelled down the esophagus via peristaltic contractions
- LES relaxes and bolus enters the stomach
- LES closes afterwards (contracts)
Which phase of swallowing triggers the swallow reflex?
- Oral Phase
Which phases of swallowing are under voluntary control vs. involuntary control?
Voluntary control: Oral Phase
Involuntary control: Pharyngeal Phase and Esophageal Phase
Peristalsis
- Coordinated series of muscle constrictions and relaxations that make up the propulsive motility patterns
Orad Region:
- Circular muscles contract behind the bolus & longitudinal muscles relax behind the bolus
Caudad Region:
- Longitudinal muscles contract in front of the bolus
- Circular muscles relax in front of the bolus
Species differences in Esophageal Muscle Composition:
Dogs, Cattle and Sheep:
- Striated muscle throughout esophagus
Cats, Horses:
- Striated muscle UES
- Smooth Muscle LES
Describe the two types of innervation in the esophagus.
Striated Muscle is under the control of the somatic nervous system
- Vagus n.
- Innervates the muscle directly
Smooth Muscle:
- Under direct control of the enteric nervous system
- Myenteric plexus (preganglionic nerves)
- Postganglionic nerves synapse on the muscle
NT for the contraction of circular muscle in the esophagus
- ACh
NT for the relaxation of circular muscle in the esophagus
- Nitric Oxide (NO)
- VIP
1st Peristaltic Contraction is initiated by:
- CNS Swallow Center
2nd peristaltic contraction:
- ENS
- In cases where food remains in the esophagus or there is gastric reflux
What are the functions of the upper esophageal sphincter and the lower esophageal sphincter?
Both have high pressure to prevent reflux and remain closed unless food is passing
Intraesophageal pressure = intrathoracic pressure
- Below atm pressure
UES:
- Under the control of the swallow reflex
- Deliver bolus to stomach
- Prevents air from entering upper esophagus
LES:
- Prevents gastroesophageal reflus
- Transient LES relaxation occurs during burping and vomitting
- Under tonic contraction at resting tone
Name a disease that is associated with the dysfunction of the esophagus.
Megaesophagus
- Generalized dialation of the esophagus
- Weak peristaltic contractions
- Normal LES tone
Achalasia:
- Issue with LES
- Fails to undergo relaxation
- Back up of ingested meal
Orad Region of the Stomach
- Fundus and Body
- Proximal region
- Stores ingested food
- Little Mixing
- Under tonic contraction
Caudad Region of the Stomach
- Distal Region
- Antrum
- Breaks up ingesta
- Mixing and propulsion
- Phasic contractions
Contractions of the Proximal Stomach
Fundic Accommodation
- Distension of the GI wall = Increased gastric lumen pressure
- Tonic contraction of the proximal region of the stomach and LES under resting conditions
- Arrival of ingesta
- Regions undergo relaxation
