LECTURE 6 - oesophageal function Flashcards
what muscle is in the upper 1/3 of the oesophagus, UOS, pharynx
striated muscle
what muscle is in the lower 2/3 of the oesophagus, LOS
smooth muscle
what state are sphincters at resting state
closed- and relax intermittently and open by normal physiological functioning
how fast is the pharyngeal swallow
<1sec
what controls the pharyngeal swallow
skeletal muscle contraction is coordinated by the swallowing centre in the medulla
what is the resting pressure of the UOS
30-200mmHg
what does the pressure in the UOS decrease (3 things)
- decreases the entry of air into the oesophagus and insufflating the stomach
- decreases reflux of the contents into the pharynx and larynx during oesophageal peristalsis
- decreases gastric reflux
how long does the UOS relax during the pharyngeal swallow
0.5-1s
what is primary peristalsis
initiated by swallowing
continuation of pharyngeal contraction
what is secondary peristalsis
not induced by swallowing
result of the stimulation of sensory receptors in the body of the oesophagus
involuntary
what is the nervous control of oesophageal peristalsis
- parasympathetic and sympathetic NS (autonomic)
- enteric nervous system= plexus of nerves embedded in the wall of the GI tract
- —- submucosal plexus
- —– myenteric nerve plexus
what is the resting pressure of the LOS
20-35mmHG
what is the action of the LOS
relaxes 1-2 sec after swallowing then hypercontracts
what happens immediately following the relaxation of LOS
receptive relaxation of the fundus of the stomach
when else does the LOS contract
relaxes unrelated to swallowing- transiently when upright- mediated by the vagus nerve- releases air from the stomach
what are the 3 phases of swallowing
`1. oral phase
- pharyngal phase
- oesophageal phase
is the oral phase voluntary or involuntary
voluntary
what are the 2 subphases of the oral phase
- prepartory phase- mastication, saliva
2. transfer phase- food propelled into pharynx
is the pharyngeal phase voluntary or involuntary
involuntar
what type of muscle is in the oral phase, pharyngeal phase, oesophageal phase
oral- striaged
pharyngeal- striated
oesophageal- smooth
what is involved in the pharygeal phase
bolus enters pharynx and descends through the pharynx by peristalsis
UOS relaxes and bolus leaves pharynx
in the pharyngeal phase which 3 passages have to be closed and how are they closed
- mouth- tongue pushes against palate sealing off back of mouth
- upper airway- soft palate elevates and the proximal pharyngeal wall moves medially
- lower airway- closed by the epiglottis swinging down and the vocal cords and arytenoids adducting
is the oesophageal phase volunatary or involuntary
involuntary
what happens in the oesophageal phase
UOS relaxes, bolus enters oesophagus, oesophageal persitalsis initiated
what makes up the superior border of the oral cavity
hard palate and soft palate
what makes up the inferior border of the oral cavity
geniohyoid and mylohyoid muscles supporting the floor of the mouth
what makes up teh anterior and lateral borders of oral cavity
labium (lip)
cheek
body of tongue
what makes of up the post border of oral cavity
uvula
tonsils (palatine and lingual)
root of tongue
what are the cavities descending down from the nasal cavity
nasal cavity - nasopharynx - oropharyx- hypopharynx- oesophagus
what is gastro-oesophageal reflux disease
an extension of what is a normal physiological process
the LOS usually transiently opens outside swallowing however this become unregulated and leads to symptoms
ie when LOS relaxations become tooo frequent resulting in symptoms
As a result gastric contents move into the oesophagus which is erosive to the oesophagus and damages the epithelim
what are other contributing mechanisms to GORD
- disordered gastric motility= more acid in fundus region of stomach
- hiatus hernia = when there is a reservoir of acid close to teh LOS which may impair its funcitoning
- impaired oesophageal peristalsis- reduced clearance
- hypotensive LOS= LOS doesn’t contract tightly enough
what is a hiatus
an opening in the diapragm where the oesophagus passes through to join the stomach
the diaphragm acts as additioanl suppport ( like a sphincter contracting aroudn teh GO junction
what is a hernia
when part of an organ protrudes through an opening in the muscle tissue meant to hold it in place
a hiatus hernia is?
when part of the stomach bulges up into the chest through the hiatus
why do symptoms occur in GORD
The pH in the oesophagus is normally 6-7 but in the stomach the contents are 1-2 (without being buffered by food)
the squamous epithelium in the oesophagus can’t handle the pH of the gastric contents -
OESOPHAGEAL NERVE FIBRES GIVE A SENSTION OF BURNIGN DISCOMFORT
what are the 2 complications of GORD
- oesophageal stricture
2. Barrett’s oesophagus
what is oesophageal stricture
= scarring from repeated acid exposure and ulcreation which leads to dysphagia (difficulty swallowing) often fibrous
what is Barrett’s oesophagus
= damage to the oesphageal epithelium by chronic acid expsure. change from squamous–> columnar lined epithelium (intestinal metaplasia)
Barrett’s is a risk factor for oesophageal cancer (adenocarcinoma)
describe the progresssio of Barrett’s to cancer
squamous oesophagus –> chronic inflammation –> barretts metaplasia –> low grade dysplasia –> high grade dysplasia –> invasive adenocarcinoma
what are the 2 types of oesophageal cancer
- adenocarcinoma
2. squamous oesophagus
describe the adenocarcinoma variant of oesophageal ancer
more common in western countries
more likely to be in the distal oesophagus (GO junction)
GORD –> Barrett’s –> cancer
describe the squamous cell carinoma variant of oesphageal cancer
due to smoking, alcohol, diet
more likely to be higher up in the oesophagus
what are the 2 categories of oesophageal conditions
- structural= anatomic abnormaility
2. motility= problem with nerves and muscle
what are some examples of structural oesophageal conditions (8)
ZAC UR ERS
- Zenker’s diverticulum
- adenocarcinoma
- oesophageal candidas
- Ulceration
- Ring/web
- Eosinophilic oesophagitis
- Reflux oesophagitis
S. Stricture
what is ring/web
on the internal aspect of the oesphagus causing obstruction
membrane grows inwards and constricts lumen
what is eosinophilic oesophagitis
when the eosinophils infiltrate the epithelium of the oesophagus
what is Zenker’s diverticulum
the faliure of the UOS to relax causing a build up in pressure in the pharynx
if the oesphageal wall is already weakened it may bulge outwards
This then creates a pouch which food can get stuck in
what are the 3 motility oesophageal conditions
DAS
- Diffuse oesophageal spasm
- Achlasia
- Schleroderma
what is diffuse oesophageal spasm
non- peristaltic or simultaneous onset of contractions in the oesophagus
ie corckscrew oesophagus
what is achlasia
degeneration of nerves in the oesophagus
- ganglionic cells in the myenteric plexus
- loss of inhibitory neurons in LOS that switch off tonic contractions
what is scleroderma
CT disease
hardening of the mucosa and submucosal layers
affects SM and nerves of oesophagus turning it into a rubbery hose
- absent peristalsis= weak contractions= complete loss of los tome
- severe dysphagia, severe reflux
what is the difference between structural and motility oesophageal conditions
motility conditions are ore likely to present with dysphagia, be intermittent and may affect both solids and liquids
motility= problems with nerves and muslce structural= problems with anatomy
