Oesophagus and its disorders Flashcards
Describe the anatomy of the oesophagus (3)
- Fibromuscular tube (25cm) of striated squamous epithelium
- Lies posterior to the trachea
- Begins at end of laryngopharynx and joins stomach a few cm from diaphragm (at the cardiac orifice of the stomach)
What does the oesophagus secrete?
Mucus
What promotes the transport of ingested food into the stomach?
- This is a highly coordinated muscular process; involves contraction and relaxation of the oesophagus which transports the food through the GIT
- Relaxation of the sphincters (UOS and LOS)
What muscle surrounds the oesophagus and at what positions?
- Skeletal muscles surround the oesophagus below the pharynx (the upper third)
- Smooth muscles surround the lower two thirds
What are the two sphincters of the oesophagus?
Describe there structures
Give the intrinsic and extrinsic component oF the LOS
Upper oesophageal sphincter (UOS): striated muscle;
Musculo-cartilaginous structure
Constricted to avoid air entering the oesophagus
• Lower oesophageal sphincter (LOS): smooth muscle; acts as a flap valve
LOS = area of high pressure zone
LOS has intrinsic and extrinsic components
Intrinsic component: oesophageal muscles; under neurohormonal influence
Extrinsic component: diaphragm muscle (adjunctive external sphincter)
The lower oesophageal sphincter has intrinsic and extrinsic components.
What are the intrinsic components of the LOS?
- Thick circular smooth muscle layers and longitudinal muscles
- Clasp-like semi-circular smooth muscle fibres on the right side
Myogenic activity (some resting tone), but less ACh-responsive - Sling-like oblique gastric (angle of His) muscle fibres on the left side
Working in concert with the clasp like-semicircular smooth muscle fibres, help to prevent regurgitation- responsive to cholinergic innervation
Angle of His is poorly developed in infants as it makes a vertical junction with stomach, hence why reflux is common in infants
What are the extrinsic components of the LOS?
Crural diaphragm encircles the LOS
= Forms channel through which oesophagus enters the abdomen
Fibres of the crural portion of the diaphragm possess a “pinchcock-like” action (extrinsic sphincter; diaphragmatic sphincter)- myogenic tone
Describe the innervation of the oesophagus
Involvement of cholinergic (i.e. via ACh) and non-cholinergic, NANC innervation in the control of tone of the lower oesophageal sphincter
Neural control of the oesophageal sphincters
- Acetylcholine, SP: contraction of intrinsic sphincters
- NO and VIP: relax the intrinsic sphincters
- Extrinsic and intrinsic sphincters work in concert to push the food into the stomach
Describe other nerves of the oesophageal plexus
DVN: dorso vagal nucleus;
NA: nucleus ambiguus;
NTS: nucleus tractus solitarius
Describe Oesophageal motor innervation
What 2 post-ganglionic fibres in the myenteric plexus does ACh affect?
The striated muscle of the upper oesophagus is innervated directly by the somatic efferent cholinergic fibres of the vagus nerve originating from the nucleus ambiguus.
Smooth muscle of the distal oesophagus is innervated by the preganglionic vagus nerve fibres from the dorsal motor nucleus. ACh affects two types of post-ganglionic neurons in the myenteric plexus: excitatory cholinergic neurons and inhibitory nitrinergic neurons via NO, VIP
Describe the functions of the oesophagus?
- Swallowing (deglutition)
* Conveys food and fluids from pharynx to stomach
How is swallowing initiated?
- Voluntary action – collect material on tongue and push it backwards into pharynx (skeletal muscle, mucus membrane)
- Waves of involuntary contractions push the material into oesophagus
Where does food move?
Food moves from Mouth→oropharynx →laryngopharynx→oesophagus and stomach
What reflex responses are initiated to swallow?
- Reflex responses
- Inhibition of respiration (breathing)- nasopharynx is closed off
- Closure of glottis (around the vocal cords) by epiglottis
- Prevents food from entering the trachea
- Ring of peristaltic waves (4cm/sec) behind the material moves it towards the stomach
- A second wave of peristalsis moves any food remnants along
What is swallowing difficulty caused by?
Swallowing difficulty (oropharyngeal dysphagia) is caused by the inability of the UOS to open or discoordination of the timing between the opening of UOS and the pharyngeal push of ingested bolus
When food passes through the oesophagus when does the UOS and LOS open and close?
What happens during secondary peristalsis
Relaxation of upper oesophageal sphincter (UOS) – food passes
- UOS closes as soon as food passes
- Glottis opens
- Breathing resumes
Lower oesophageal sphincter opens and stays open throughout swallowing
LOS closes after material has passed
A large food material does not reach the stomach after the first peristaltic wave
Stimulation of receptors upon distension of the lumen of the oesophagus by the food → repeated waves of peristalsis (secondary peristalsis)
Is secondary peristalsis of any benefit?
What prevents the reflux of gastric contents
- LOS – closes after material has passed
- “Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus (side-to-side compression between “2 pillars” of the crus)
- Plug-like action of the mucosal folds in the cardia– occludes the lumen of the gastro-oesophageal junction:
- Abdominal pressure acting on the intra-abdominal parts of the oesophagus
- Valve-like effect of oblique entry of oesophagus into stomach – in adults only
Sphincter muscles of UOS and LOS = strong circular muscles; act as valves to control the movement of the food mass aborally (forward direction); prevent reflux by forming an opening when relaxed and closing completely when contracted
Overall, there is an anti-reflux barrier in the region of gastro-oesophageal junction
Give an overview of the types of oesophageal disorders
- Disorders of motility or peristalsis of oesophagus (assess the motor function of the UOS, LOS and oesophageal body) (achalasia)
- Assess cause of regurgitation (e.g. reflux of stomach acids into oesophagus); weak LOS (GORD)
- Aphagia (determine cause of swallowing difficulty)
- Abnormal oesophageal contractions and food is not effectively reaching the stomach (oesophageal spasm)
- Diffuse oesophageal spasm - chest pain coming from oesophagus (~angina)
What is an achalasia?
What does it result in ( and show on oesophageal)?
What does it result in?
- Impaired LOS relaxation (spasms)
- Can be accompanied by impaired peristalsis (sphincter spasms);
- Food and liquids fail to reach the stomach – delayed opening of LOS;
- Results in dilation of oesophageal body with distal narrowing (bird’s beak appearance) of the barium-filled oesophagus on oesophagram;
- Long period of sporadic dysphagia (difficulty swallowing);
- Regurgitation of food
Describe the aetiology of achalasia
- Disorders of motility or peristalsis of oesophagus (assess the motor function of the UOS, LOS and oesophageal body)
- Damage to the innervation of oesophagus
- Degenerative lesions to the vagus nerve and loss of myenteric plexus ganglionic cells in the oesophagus
What are the symptoms of achalasia?
• Dysphagia
Difficult or painful swallowing
• Vomiting
• Heartburn
Retrosternal burning sensation due to oesophageal dysmotility
Retention of ingested (acidic) food;
Generation of lactic acid in the process of decomposition of retained food;
also heartburn could be caused by the retention of small quantities of acid refluxed in the oesophagus due to poor emptying and incomplete relaxation of LOS
How do doctors diagnose achalasia?
- Barium radiography (barium swallow): dilatation of oesophagus with beak deformity at lower end -Evaluates the entire swallowing channel (mouth, pharynx, and oesophagus)
- Oesophageal manometry: absent peristalsis
Why is Oesophageal manometry performed?
To determine the cause of non-cardiac chest pain
To evaluate the cause of reflux (regurgitation) of stomach acid and other contents back up into the oesophagus (GORD?)
To determine the cause of difficulty with swallowing food (does UOS/LOS contract and relax properly?)
Allows evaluation of strength of coordination of muscle contractions
Relaxation function of LOS
What are the normal results of oesophageal manometry
Normal LOS pressure and normal muscle contractions upon swallowing
Low LOS pressure suggests GORD, but GORD can occur in individuals with normal LOS pressure
What does high LOS pressure suggest?
Pressure of LOS <26mm Hg is normal, >100 mm Hg is considered achalasia, > 200 mm Hg is nut cracker achalasia
What would normal results of oesophageal manometry show?
The pressure of the muscle contractions that move food down the oesophagus is normal
The muscle contractions follow a normal pattern down the oesophagus
Normal pressure of the LOS is about 15 mmHg, but
*when the LOS relaxes to let food pass into the stomach, the pressure is less than 10 mmHg
What are abnormal results of oesophageal manometry characterised by?
Presence of muscle spasms in the oesophageal body
Presence of weak contractions along the length of the oesophagus
*The LOS pressure is less than 10 mmHg (GORD?) – do not confuse these 2
Characterised by high LOS pressure which fails to relax after swallowing
Lack of a coordinated LOS relaxation in response to swallowing.
What happens in reflux in normal individuals?
When does it happen?
What does saliva do to reflux acid?
What does a low rate of salivation cause/ lack of ability to swallow saliva?
- Often occurs after meals in normal individuals (- transient spontaneous LOS relaxation, tsr);
- Reflux usually stimulates salivation
- Saliva is an effective natural antacid - dilutes and neutralises refluxed gastric contents
- Low rate of salivation; lack of ability to swallow own saliva →prolongation of contact of refluxed material with oesophagus → Gastro-oesophageal reflux disease due to oesophageal irritation and oesophageal damage
What is Gastro-oesophageal reflux disease (GORD)?
GORD is when reflux is more frequent and troublesome
Low rate of salivation; lack of ability to swallow own saliva →prolongation of contact of refluxed material with oesophagus → oesophageal irritation and oesophageal damage.
What are the causes of refluxes with those who have GORD?
1 Transient spontaneous LOS relaxation (tsr)
98% of reflux events in normal individuals is associated with transient spontaneous relaxation (tsr) of LOS
- Resting LOS pressure is too weak to resist the pressure within the stomach
- Sudden relaxation of the LOS that is not induced by swallowing
What factors contribute towards the severity of GORD?
- Weak or uncoordinated oesophageal contractions (oesophageal irritation from reflux disease itself?)
– prolonged duration of contact of refluxed digestive contents with oesophagus - Length of time the oesophagus is exposed to gastric acid
↑ Gastric acid secretion coupled with presence of bile in gastric contents → severe oesophageal damage - Amount of pressure placed on the anti-reflux barrier
Reflux occurs after eating, lying down (supine), and when there is delayed gastric emptying
Impaired gastric emptying alone can cause severe GORD
How can GORD be investigated?
Low dose proton pump inhibitor (PPI) challenge is 1st line
Upper GI endoscopy
Manometry
24-hr ambulatory pH monitoring
How does GORD and pregnancy interact?
- Foetus increases pressure on abdominal contents
- Pushes terminal segments of oesophagus into thoracic cavity
- Last trimester of pregnancy is associated with increased abdominal pressure and this forces gastric contents into oesophagus
- Heartburn subsides in the last months of pregnancy as uterus descends into pelvis
What causes normal heartburn?
May occur in some individuals upon eating large meals
Less efficient LOS
Gastric contents episodically refluxed into oesophagus
Heartburn
Ulcer, scarring, obstruction or perforation of lower oesophagus
on image
What are the long term effects of GORD?
Oesophagitis, oesophageal strictures
Squamous cell carcinoma
Barrett’s syndrome - this may predispose someone to oesophageal adenocarcinoma
Oesophageal ulcer
Manometry will be ordered if you have symptoms of:
Heartburn or nausea after eating (GORD)
Problems swallowing [feeling that food is stuck behind the breast bone (achalasia)]
How can GORD be managed?
Life-style changes - raise head of bed at night, weight loss, modify food
↓ Intake of foods and drink which cause symptoms
Anti-reflux surgery (fundoplication – wrap fundus around LOS)
Take antacids
H2 receptor antagonists and proton pump inhibitors
Metoclopramide/domperidone – may enhance peristalsis and help gastric acid clearance
List of lifestyle changes that help alleviate the symptoms of GORD
Some people need to avoid large meals Lose weight (if overweight) Avoid foods that increase gastric acidity Avoid foods that slow gastric emptying Avoid lying down after meals - elevate the head of the bed Avoid some drugs and smoking Decease fat intake
Basically, if you know what aggravates the symptoms, you can try to implement life-style changes that may help alleviate the onset
How can antacids be used to treat GORD?
Neutralise gastric acid; ↑ pH of gastric lumen
Inhibit peptic activity and stop acid secretion
What are the side effects of antacids?
Magnesium salts→ diarrhoea Aluminium salts→ constipation Use a mixture of 2 to ensure bowel function Combine alginates (e.g. gaviscon) with antacids for oesophageal reflux Alginic acid + saliva form a raft which floats on content of gastric lumen and protects the oesophageal mucosa from reflux
All of the above agents ↓ acid secretion and help heal the ulcer, but removal of H. pylori is essential to stop ulcer returning.
Why study oesophageal disorder?
Complications of GORD
Oesophagus has squamous mucosa
- Acid reflux → desquamation of oesophageal cells (injury of squamous mucosa)
- ↑ cell loss → basal cell hyperplasia
- Excessive desquamation → ulceration
- Ulcers may haemorrhage, perforate or heal by fibrosis with strictures
This leads to Barrett’s oesophagus and oesophageal cancer
