Lecture 6; Oesophageal function Flashcards
Describe the oesophagus;
Pharynx, upper oesophogeal sphincter (UOS), upper 1/3 of oesophagus - striated muscle. Lower 2/3 of oesophagus, lower oesophageal spincter (LOS) - Smoother muscle
Are sphincters generally closed or open etc?
A sphincter is generally closed at rest in a state of tonic contraction, relaxing intermittently as required by normal physiological function
Describe the process of swallowing the upper oesophagus;
- <1s - Skeletal muscle contract 30-40cm/s - Co-ordinated by medulla - UOS closure can raise pressure to 30-200mmHg - UOS relaxation occurs for <1s allowing, swallowing, belching and vomiting.
What does UOS do?
- Decrease entry of air into oesophagus and insufflating (distending the stomach) - Reflux of contents in pharynx and larynx during oesophageal paristalsis - Gastric reflux
Describe the muscle of the oesophagus;
Upper 1/3 striated Skeletal muscle. Lower 2/3 Smooth muscle only
What is primary and secondary peristalsis?
Contraction above and below the bolus caused by swallowing (Primary). Secondary caused by stimulation of sensory receptors in the oesophagus by retained bolus or gastric acid (Not swollowing related)
Describe peristalsis and the muscle layers;
Circular muscle layer; Contraction above and relaxation below bolus Longitudinal muscle layer; Shortens oesophagus during peristalsis
Describe the innervation of the oesophagus;
- Receives ENS input. - Submucosal plexus - Myenteric plexus (between muscle layers) Can function autonomously i.e reflexes Communicates with parasymp and symp branches of ANS.
Describe the characteristics of the LOS function;
- Smooth muscle 2-4cm - 20-35mmHg when closed - LOS relaxes 1-2s after swallowing and lasts 5-10s before hypercontracting - Close anatomical relationship to squamo-columnar junction
When else does LOS relax?
- LOS also relaxes transiently; - Release stomach air - Lying down (night time gastric reflux) Occurs regularly when upright mediated by vagus nerve
What are the phases of swallowing?
Oral Phase - Striated muscle (Voluntary) Pharyngeal phase - Striated muscle (Involuntary) Oesophogeal phase - Striated and smooth muscle (Involuntary)
What is the oral phase of swallowing?
Preparatory phase to form food bolus - Mastication - Enzymes - lubrication AND transfers food to pharynx Teeth and tongue work hard,
What is the pharyngeal phase of swallowing?
- <1s - Bolus moves through pharynx at 30-40cm/s - UOS relaxes
What passages must be closed to achieve the pharyngeal phase of swallowing?
- Mouth - Upper airway (nose) - Lower airway (trachea)
Describe how the passages are closed off during the pharyngeal phase;
- Tongue pushes against palate closing oropharynx - Soft palate elevates, proximal pharyngeal wall moves medially closes off upper airway (nasopharynx) - Epiglottis swings down, vocal cords and arytenoids adduct, seals off lower airway
What is the oesophageal phase?
- UOS relaxes - Bolus enters oesophagus - Oesophageal peristalsis initiated
Where is swallowing controlled?
- Cortex and brainstem
How is the brainstem involved in swallowing?
Brainstem receives sensory input from receptors in posterior mouth and upper pharynx and also innervates swallowing muscles via cranial nerves.
When do most gastro-oesophogeal episodes occur?
During transient relaxation of the LOS. This is physiological but becomes pathological when too much gastric juice also refluxes into oesophagus causing symptoms / disease
What can cause acid in the oesophagus i.e heart burn?
Disordered gastric motility - More acid in fundus of stomach
Hiatus hernia - Can result in reservoir of acid close to LOS or impair LOS function Impaired oesophageal peristalsis
Hypotensive LOS i.e not contracting tight enough - Caused by caffeine, alcohol, chocolate, fats.
Certain meds; Beta-blockers, nitrates, Ca chan blockers
What is a hiatus hernia?
Hiatus = Opening in diaphragm (Diaphragm aids GO constriction.) Hiatus hernia is when stomach protrudes through hiatus.
Why does heartburn occur?
Empty stomach pH can be 1-2, squamous epithelium not designed to handle this. Sensitivity highly variable
Whats the name of the disorder for gastric reflux?
GORD Gastric oesophageal reflux disorder
What are some complications of GORD?
Reflux oesophagitis Oesophageal stricture Barretts oesophagus
