Feb15 M1-Physiology - Esophagus Flashcards
3 phases of deglutition
oral, pharyngeal, esophageal
2 types of dysphagia
- dysphagia can be coughing, chocking if oropharyngeal
- or regurg and food stuck if esophageal
2 causes of dysphagia
mechanical obstruction (or structural abnormality) or neuromotor defect
muscles in esophagus
proximal = SKM, then SKM and SM transition then SM (LES is SM)
oral phase charact and 4 steps
only voluntary one
- moistening
- mastication
- through formation (tongue moves food and holds liquid)
- tongue mvmt posteriorly to move bolus to the back and trigger swallowing
site of the voluntary center for swallowing
precentral gyrus (initiates swallow)
precentral gyrus linked closely to what
deglutition centre in the medulla, responsible for involuntary coordination
4 causes of anomalies in the oral phase of swallowing
- neurom defect
- congenital (cleft palate)
- obstruction (ex. neoplasm)
- trauma or inflammation
3 prerequisites to the oral phase of swallowing
- make pressure
- prevent dissipation of that pressure
- decrease resistance (for bolus passage)
when swallowing becomes automatic
when bolus touches tonsils
4 steps of pharyngeal phase to protect airways (nasal reflux)
- raise soft palate.
- raise base of the tongue
- vocal cords come together (are below glottis)
- tilting forward of epiglottis
3 steps of pharyngeal phase to move from pharynx to esophagus
- forward AND upward movement of the larynx + relaxation of esophagus
- propagated contraction of pharyngeal constrictors
- relaxation of UES
what is needed for OPENING of UES
- forward AND upward movement of the larynx + relaxation of esophagus
- relaxation of UES (relaxation doesn’t mean opening)
pharyngeal phase 7 steps: sensory afferents to the medulla (medullary swallowing center) travel in what cranialnerves
5, 9, 10 (10 is vagus)
pharyngeal phase 7 steps: motor efferents from the medulla (medullary swallowing center) travel in what cranial nerves
5, 7, 9, 10 (vagus), 12
other mechanism to protect airways by medullary deglutition center (or central pattern generator)
deglutition apnea (last a us): the deglutition centre inhibits the respiratory centre in the medulla
3 types of things causing oropharyngeal dysphagia
- obstruction or increased resistance (intra + extra luminal obstructions + xerostomia)
- myogenic
- nervous system
other name for UES
cricopharyngeus muscle
innervation of UES and consequence
vagus (PSS) impulse via a PRIMARY ORDER neuron. UES has nicotinic Ach receptor: MAKES THE MUSCLE CONTRACT
how to make pharyngeal constrictors (muscles) (UES) relax
stop vagus Ach (N) input to the UES
what are the ICCs (interstitial cells of Cajal)
cells of the myenteric plexus (Auerbach’s) located between inner circular and outer longitudinal
2 plexuses of ENS
submucosal plexus (Meissner's) : PSS myenteric plexus (Auerbach's): SS and PSS to muscles
dual innervation of smooth muscle in the gut
vagus to Auerbach’s plexus: Ach (Nicotinir R)
neuron in Auerbach’s plexus to SM: Ach (muscarinic R on muscle (+) or inhibitory ntr like NO on muscle (-))
vago-vagal reflex present where
between deglutition centre and SKM upper esoph OR deglutition centre and SM and back to deglutition centre via vagus afferent
entero-enteric reflex is where
between Auerbach’s plexus neurons and SM (distal esophagus and LOS)
forces involved in esophageal phase of deglutition
- pharyngeal momentum
- gravity
- peristalsis
primary peristaltic wave def
wave of peristalsis when we swallow. 8-10 sec to propagate. part of deglutition reflex
2 high pressure zones in the esophagus
UES and LES
pressure changes in esophagus in response to primary peristalsis
causes propagation of a pressure complex (30-80 mmHg) that takes 10s
2 nuclei of the medulla giving the vagus
nucleus ambiguus and dorsal motor nucleus of the vagus
what generates peristalsis
central pattern generator (deglutition centre) of medulla relaxes downstream of bolus and contracts upstream of bolus
cutting vagus high in neck vs transthoracically consequence
high in neck: pharyngeal phase problem + no primary peristalsis
transthoracically: if some fibers reach ENS, ENS can continue to propagate a normal peristalsis in SM
primary peristalsis: role of vagus and ENS
vagus: initiating in proximal esophagus
ENS: continuation and propagation of primary peristalsis in distal esophagus
stimulus for primary peristalsis
pharyngeal receptors sense bolus: vago-vagal reflex
secondary peristalsis when and what
when local distension (bolus stuck or reflux) in esophagus: many waves until resolved
secondary peristalsis: innervation needed
vagus needed in upper esophagus but lower esophagus is fine with ENS
factors influencing esophageal transport (3)
- viscosity of bolus
- temperature of bolus
- posture of the subject
why temp influences transport in esophagus
vago-vagal reflex where temperature sensing fibers cause inhibition of esophageal contractions if cold
LES what forms it
phrenoesophageal ligament, diaphragm, SM of the esophagus
UES vs LES closure
UES: neurogenic (vagus)
LES: myogenic tone
UES vs LES relaxation
UES: central inhibition (Ach impulse STOPS)
LES: local neurogenic (NANC (NO))
why LES differs from rest of GI tract + characteristics (6)
is hyperfunctioning and hypersensitive 1) more collagen 2) partially contracted at its RMP (resting membrane potention) : lower RMP 3) more resistant to stretch 4) sensitive to hypoxia 5) Ca dependent 6) more sensitive to hormones and ntrs
stuff that increases LES activity and important note
gastrin (IN PHARMA DOSES)
stuff that decreases LES activity and important note
secretin, CCK (IN PHARMA DOSES) + smoking, alcohol, morphine, fat, chocolate, carminatives (mechanisms with cAMP)
one thing that lowers LES pressure at endogenous dose
progesterone
pyrosis def
heartburn
GERD leads to what changes in esophagus
metaplastic changes in mucosa (Barrett’s esophagus)
3 diseases related to GERD
- esophagitis
- Barrett’s esophagus
- hiatal hernia (as cause)
patients with GERD have what
defective secondary peristalsis + defective epithelial resistance in esophagus (damage)
3 esophageal studies
radiology, endoscopy, intraluminal pressure recording (manometry)
intraluminal pressure recording (manometry) explanation
use for dx + check dynamics of deglutition
causes of esophageal dysphagia + one to remember
achalasia**, stricture, cancer, eosinophilic esophagitis, spasm, …
achalasia def
absent esophageal peristalsis (SM) and failure of LES to relax with swallowing
achalasia pathophgy + cause + consequence
kills inhibitory NO neurons. can’t relax LES. dysphagia. cause is unkown
achalasia treatments
- SM relaxants
- botox (blocks Ach and excitation locally)
- peumatic balloon dilatation (break muscle)
- surgical myotomy (break muscle)
