Oesophagus and its disorders Flashcards
Describe the anatomy of the oesophagus.
Fibromumscular tube (25 cm) lined by striated squamous epithelium.
Lies posterior to the trachea and begins at the end of the laryngopharynx, joining the stomach a few cm from the diaphragm at the cardiac orifice.
What are the functions of the oesophagus?
Transports food from the pharynx to the stomach
Secretes mucus which lubricates food and neutralises any acid that may come up from the gut.
What are the 3 parts if the oesophagus?
cervical
thoracic
abdominal
Describe the muscle structure of the oesophagus.
Skeletal muscle surround the upper portion of the oesophagus
Smooth muscle surrounds the lower two thirds.
Describe the structure of the upper oesophageal sphincter.
Musculo-cartilaginious structure composed of striated skeletal muscle and constricts to avoid air entering into the oesophagus.
Describe the structure of the lower oesophageal sphincter.
Lies close to the diaphragm and is composed of smooth muscle and acts as a flap
Has intrinsic and extrinsic components:
- Intrinsic: oesophageal muscles under neurohormonal influence (NO and Ach control level of constriction)
- Extrinsic: diaphragm muscle acts as a pinch cock in terms of restriction of food from the stomach moving up the stomach and damaging epithelial cells
- Malfunction of intrinsic and extrinsic components of LOS lead to GORD, where acidic chyme can move up the oesophagus
Describe the components of the lower oesophageal sphincter.
INTRINSIC
- composed of thick oesophageal smooth muscle and have myogenic activity (some resting tone), but less responsive to Ach
- oblique and sling fibres of the stomach help to prevent regurgitation; these fibres are very responsive to cholinergic innervation
EXTRINSIC
- formed by the cural diaphragm encircling the LOS, forming a channel through which the oesophagus enters the abdomen
- fibres of the cural diaphragm posses pinch cock like action, blocking any reflux of acidic chyme into the oesophagus (these fibres function as an adjunctive external sphincter “diaphragmatic sphincter” to act as an anti-reflux barrier like the LOS).
What is the angle of His?
Acute angle created between entrance into the stomach (cardia) and the oesophagus
it forms a valve along with the LOS, preventing reflux of duodenal bile, enzymes and gastric acid from entering the oesophagus, where they can cause irritation of the oesophageal lining, inflammation and in extreme cases Barrett’s Oesophagus.
What is the structure of the angle of His in an infant?
Underdeveloped in infants as it makes a vertical function with the stomach, hence why reflux is more common in infants.
Describe muscle contractions in a blood filled oesophagus.
Longitudinal muscle running along the outside contracts
Circular muscle running along the inside relaxes.
Describe how the oesophagus is innervated.
Cholinergic innervation of the oesophagus (Ach) and Ach plays a part further up.
Down-stream is NANC innervation to control the tone of the LOS.
Describe the neural control of oesophageal sphincters.
Ach and substance P contract the intrinsic sphincters.
NO and VIP relax the intrinsic sphincters.
How is the striated muscle of the upper oesophagus is innervated?
Striated muscle of upper oesophagus is innervated by somatic cholinergic fibres (Ach) of the vagus nerve originating from the nucleus ambiguus.
How is the smooth muscle of the lower oasophagus innervated?
Smooth muscle of distal oesophagus is innervated by pre-ganglionic nerve fibres from the dorsal vagal nucleus and NTS
Ach then acts on post-ganglionic fibres of the myenteric plexus:
- excitatory cholinergic neurones
- inhibitory nitrinergic neruones via NO/VIP.
What triggers swallowing?
By afferent impulses in the trigeminal, glossopharyngeal and vagus nerves
Efferent fibres then go back to the pharyngeal musculature and the tongue
*There is integration of impulses in the NTS, nucleus ambiguus and the dorsal vagal nucleus.
What are the voluntary and involuntary actions of swallowing?
Voluntary action is the collection of material on the tongue and pushing it backwards into the pharynx.
Involuntary action are the waves of involuntary contractions pushing the material into the oesophagus once the food passes the pharynx.
Describe the path that food takes.
Mouth Oropharynx Laryngopharynx Oesophagus Stomach
What effect does swallowing have on respirations?
Respiration (breathing) inhibited when swallowing as nasopharynx gets closed off.
What effect does swallowing have on the glottis?
Glottis around vocal cords closes by the epiglottis folding over it, preventing food entering trachea.
Describe the peristaltic waves in swallowing.
First wave of peristalsis (swallow induced) will move food towards the stomach (4 cm/sec)
Second wave of peristalsis (stimulated by distension of oesophagus by food) moves any food remnants in the oesophagus along.
What is Oropharyngeal dysphagia?
Difficulty with swallowing because UOS unable to open or discoordination of the timing between the opening of UOS and the pharyngeal push of ingested bolus.
Give the mechanisms that prevent gastric reflux.
- LOS closing after food passing
- Abdominal pressure acting on the intra-abdominal parts of the oesophagus prevents reflux
- Angle of His acts a valve to prevent reflux (only in adults)
- Diaphragmatic “extrinsic” sphincter exhibits pinchcock effect helping to block material entering into oesophagus
- Circular muscle of EOS and LOS act as valves to control movement of food aborally (prevent reflux by forming an opening when relaxed and closing completely when contracted).
When do LOS and EOS relax?
During swallowing.
What is Transient Spontaneous Relaxation (TSR)?
Relaxation of LOS and EOS without a swallow.
What is Achalasia?
Absence of peristalsis, spasms of LOS and failure of LOS to relax (causes hypertensive LOS)
absence of peristalsis causes dilation of oesophageal body, with distal narrowing
causes sporadic dysphagia due to stuck food, regurgitation of food and spasm disorders.
What is the Normal LOS pressure?
15 mmHg (without swallowing)
10 mmHg (swallowing)
What is the LOS pressure indicating achalasia?
high LOS pressure
> 100 mmHg
What is the LOS pressure during Nutcracker Achalasia?
LOS pressure >200 mmHg
What is the cause of achalsia?
Damage to innervation of the oesophagus:
-may be degenerative lesions of the vagus nerve and a loss of myenteric plexus ganglionic cells in the oesophagus.
What are the symptoms of acalasia?
Dysphagia
Vomiting
Heartburn
How is achalasia diagnosed?
1) Radiography (barium swallow):
- X-ray shows dilation of oesophagus body with a ‘beak’ deformity at lower end
2) Oesophageal Manometry
- tests if oesophagus is contracting and relaxing properly; in achalasia there is absent peristalsis.
Describe reflux in normal individuals.
Often occurs after meals in normal individuals due to transient spontaneous relaxation of LOS, however the reflux stimulates salivation, which is an effective natural antacid, diluting and neutralising refluxed gastric contents.
What is Gastro-oesophageal reflux disease (GORD)?
GORD happens when reflux is more frequent and troublesome, leading to low rate of salivation, lack of ability to swallow own saliva, prolongation of contact of refluxed material with oesophagus causing oesophageal irritation and oesophageal damage.
What are the causes of GORD?
- Resting LOS pressure too weak to resist pressure within stomach
- Sudden relaxation of the LOS that is not induced by swallowing (TSR)
- Malfunction of extrinsic and intrinsic components of LOS
Give some factors associated with GORD.
Pregnancy
Obesity
Fat, chocolate, coffee, alcohol
Large meals, tomatoes, orange juice, onions
Cigarrettes
Drugs (anticholinergics, CCBs and nitrates)
Give Pathophysiology and Clinical Features of GORD.
- Resting LOS tone low or absent
- LOS tone fails to increase when lying flat or during pregnancy
- Poor oesophageal peristalsis causing decreased acid clearance
- Hiatus hernia impairs functioning of LOS and EOS closing mechanisms which can lead to acid reflux
- Delayed gastric emptying may also cause GORD
What is the LOS pressure in GORD?
too low
<10 mmHg without swallowing
What are the symptoms of GORD?
Heartburn and acid regurgitation
Waking up at night due to reflux irritating larynx
Dysphagia
How is GORD investigated?
- Low dose PPI is first line
- Upper GI endoscopy
- Manometry
- 24 hr ambulatory pH monitoring
How does GORD affect pregnancy?
Foetus increases abdominal pressure and this forces gastric contents (HCl) into oesophagus (especially in last trimester)
*Heartburn from GORD subsides in last months of pregnancy as the uterus descends into the pelvis.
Give Potential Long Term Effects of GORD.
Oesophagitis and oesophageal strictures
squamous cell carcinoma
Barrett’s syndrome, which may predispose someone to oesophageal adenocarcinoma
oesophageal ulcer
How is GORD treated?
LIFESTYLE CHANGES
- raising head of bed
- decreasing intake of food and drinks which precipitate attacks and cause symptoms (e.g. onions, chocolate)
- anti reflux surgery (fundoplication)
- losing weight if overweight
- avoiding large meals
- avoid smoking and some drugs
- decrease total fat intake
DRUGS
- antacids
- H2 histamine antagonists and proton pump inhibitors
- Metoclopramide and Domperidone may enhance peristalsis and and help aid gastric acid clearance
What is Antacids MOA?
Neutralise gastric acid and increase pH of lumen by inhibiting peptic activity and stopping acid secretion
What effect does Antacids treatment have on GORD?
Mg and Al salts used together to neutralise gastric acid and increase pH of gastric lumen. Also inhibit peptic activity and stop acid secretion.
Mg salts cause diarrhoea and Al salts cause constipation, which is why they are used together to ensure normal bowel function.
What should antacids be used in combination with?
Alginates (e.g. gaviscon)
What is Alginic acid (Gaviscon)?
Antacid forming a non-acid raft floating on the contents of the gastric lumen and protects oesophageal mucosa from reflux
