Swallowing, Gastric Emptying and Intestinal Motility Flashcards
Phases of swallowing
oral, pharyngeal, esophageal
Aspects of gastric motility
Receptive relaxation/Gastric accommodation, Mixing, Emptying, Migrating myoelectric complex
small intestine motility (3)
Segmentation, Peristalsis, Migrating myoelectric complex
large intestine motility (4)
Haustrations, Long-duration contractions, Mass movements
Defecation reflex
Swallowing: receptors, integration center, effectors
Deglutition
Initiated voluntarily
Reflex control of events moving food from mouth → stomach
Receptors: Touch receptors
-Primarily near opening of pharynx
Integration center: Swallowing center
-Medulla oblongata (lower pons)
Effectors: Pharyngeal and esophageal striated and smooth m.
-Cranial n.n.: pharynx and upper esophagus
-Vagus n.: lower esophagus
Swallowing: 3 Phases
Oral phase: Voluntary
-Bolus: tongue pharynx
- Pharyngeal phase: Involuntary
-Initiated by response to pressure
receptors in pharynx
-Directs bolus into esophagus via
relaxed upper esophageal sphincter (UES) - Esophageal phase: Involuntary
-Bolus from UES via peristalsis through
lower esophageal sphincter (LES) stomach
Pharynx propulsive function
food transfer to esophagus
Upper Esophageal Sphincter (UES) propulsive functions and protective effects
allows entry of food into esophagus
protects airway from swallowed material
Esophagus function and protective effects
transports bolus from pharynx to stomach
clears material refluxed from stomach
Lower Esophageal Sphincter (LES) function and protective effects
allows entry of food into stomach
protects esophagus from gastric reflux
Swallowing- oral phase
Tongue pushes bolus against hard palate
Touch receptors of the pharynx detect bolus
Swallowing reflex is initiated
Swallowing- pharyngeal phase
involuntary
Propels food from pharynx into esophagus
Respiration inhibited
1.Bolus is directed into pharynx
-Elevation of soft palate blocks entry
to nasopharynx
2.Epiglottis blocks entry to trachea
3.Pharyngeal m.m. push bolus into pharynx; UES relaxes
4.Peristaltic wave moves bolus
through UES
5. During pharyngeal stage of swallowing, respiration is
reflexely inhibited
Pressure peak travels during swallowing
pharynx -> upper sphincter of esophagus –> junction of smooth and striated muscle–> body of esophagus–> lower sphincter of esophagus
Swallowing: esophageal phase
After UES closes, LES begins to relax Primary peristaltic wave begins below UES -Reflex initiated by swallowing center Secondary peristalsis -Initiated by distention -Occurs only if primary wave is not sufficient
What kind of input modulates esophageal peristalsis?
Input from esophageal sensory fibers to the CNS
and ENS modulates both primary and secondary
esophageal peristalsis
Sphincters- general
Muscular barriers
High resting pressure in order to maintain separation
Regulate antegrade and retrograde movement
In general:
Proximal stimuli → relaxation
Distal stimuli → contraction
Facilitate unidirectional movement through G.I. tract
Coordination of:
-Other smooth muscle contractions
-Neural stimulation
-Humoral stimulation
Sphincters- general
Muscular barriers
High resting pressure in order to maintain separation
Regulate antegrade and retrograde movement
In general:
Proximal stimuli → relaxation
Distal stimuli → contraction
Facilitate unidirectional movement through G.I. tract
Coordination of:
-Other smooth muscle contractions
-Neural stimulation
-Humoral stimulation
Upper esophageal sphincter
Skeletal muscle
Regulated by swallowing center via cranial n.n.
Highest resting pressure of GI sphincters
Closed during inspiration
Limits air entry to esophagus
Lower esophageal sphincter
Smooth muscle
Primary function:
allows coordinated movement of food into stomach
prevents reflux of gastric contents into esophagus
LES resting tone:
-Intrinsic myogenic properties
-Cholinergic regulation
LES relaxation:
Intrinsic smooth muscle properties
Vagus n. (inhibition by VIP and NO)
LES relaxation occurs after UES returns to resting pressure
Swallowing or esophageal distention → decreases LES pressure
GERD
the most common symptom of
heartburn due to stomach acid reflux
into esophagus
is not a disease but a normal physiological process
stomach contents leak backwards from the stomach into the esophagus and irritates the lining of the esophagus
this occurs when the lower esophageal sphincter (LES) does not work properly
weak squamous lining of the lower esophageal section
decrease secretion of mucus and bicarbonate in saliva
Barrett’s esophagus
(pre-cancerous lesion):
it is most often diagnosed in people who have long-term GERD (chronic inflammation)
this condition is recognized as a complication of GERD
a condition in whichcolumnar cells replace squamous cell in themucosa of esophagus
the main cause of Barrett’s esophagus is thought to be an adaptation to chronic acid
exposure fromreflux esophagitis
its importance lies in its predisposition to evolve into esophagealcancer
it develops in about 10–20% of patients withchronic GERD.
Dysphagia
common problem in elderly people with difficulty
in swallowing, food getting caught in esophagus
risk of aspiration, choking and malnutrition
difficulty in swallowing due to abnormalities in:
structural - anatomical structures
- abnormal tongue, cannot propel bolus backward
- diverticula (outpouchings of pharyngeal or
esophageal wall) in which food is trapped.
functional - abnormal swallowing reflex
- neurological defect and control of oropharyngeal
swallowing, peristalsis, and esophageal sphincter
relaxation, or to defects in muscle layers.
disease state:
- neurological disorders
- stroke
- Parkinson’s disease
- myasthenia gravis
- xerostomia
Achalasia
(failure to relax):
special form of dysphagia
complete lack of peristalsis within esophagus
LES does not relax and increased LES pressure
food is retained at the level of LES
caused by:
- nerve degeneration (enteric nervous system)
- lack of NO synthase, VIP, etc
- Chagas disease (infection protozoa: Trypanosoma cruzi)
What does the radiography look like in achalasia?
bird’s beak
Incompetent LES
The LES acts like a guard that prevents anything that gets into the stomach from refluxing into the esophagus, it acts as a pressure barrier at the gastro-esophageal junction
Incompetent LES or transient relaxation of LES are the most common symptoms
of reflux. Physiologically, a well functioning LES will remain closed except in:
- primary peristalsis-within 2 sec after a swallow, leads to LES relaxation for
5-10 sec (release of NO & VIP) and then contracts
- secondary peristalsis-LES relaxation occurs as a reflex after distention of
proximal striated or more distal esophageal smooth muscle
- transient LES relaxation are not associated with pharyngeal contraction or
esophageal peristalsis and persists for more than 10 sec.
control of LES function are not completely understood
various drugs, hormones, and neuro-humoral agents produce stimulatory or inhibitory effects on the LES by binding with specific receptors
cessation of excitatory cholinergic activity and release of NO and VIP leads to LES relaxation
GERD is secondary to an incompetent lower esophageal sphincter
as the real cause to incompetent LES is not known it is sometimes referred to as idiopathic LES Incompetence
Diffuse esophageal spasms
diffuse esophageal spasms (DES) are irregular, uncoordinated, and sometimes powerful contractions of the esophagus
it is characterized by contractions that are of normal amplitude but are uncoordinated, simultaneous, or rapidly propagated
these spasms can prevent food from reaching the stomach, leaving it stuck in the esophagus
it can cause dysphagia, regurgitation and chest pain
the cause of esophageal spasm is unknown
may caused by disruption of the nerve activity that coordinates the swallowing action of the esophagus
in some people, very hot or very cold foods may trigger an episode
What does radiography look like in DES?
corkscrew appearance
