Oesophagus and its disorders Flashcards
What is the oesophagus?
→ Fibromuscular tube of striated squamous epithelium
Where is the oesophagus?
→ Posterior to the trachea
→ Beneath the cricoid cartilage
What does the oesophagus connect?
→ Begins at the end of the laryngopharynx and joins the stomach a few cm from the diaphragm
What is the oesophagus wall made from?
→ Striated muscle in the upper part
→ Smooth muscle in the lower part
→ Mixture of the two in the middle
What is the angle between the cardiac orifice and the fundus called?
→ Angle of His
What is the function of the angle of His?
→ Prevents the reflux of the contents of the stomach into the oesophagus
What is the function of the oesophagus?
→ Transports food to the stomach
→ Secretes mucus
What promotes the ingestion of food into the stomach?
→ Relaxation of UOS and LOS sphincters
→ Involves contraction and relaxation of the oesophagus
→ highly coordinated muscular process
What is the UOS for?
→ Relaxes to allow food through and closes to prevents air entering the oesophagus
What is the LOS for?
→ Remains open as long as swallowing is occurring
→ Close to prevent reflux of the stomach contents into the oesophagus
What kind of structure and muscle does the UOS have?
→ Musculo-cartilaginous structure
→ Striated muscle
What are the intrinsic and extrinsic components of the LOS?
INTRINSIC
→ Oesophageal muscles which are under neurohormonal influence
EXTRINSIC
→ Diaphragm muscles
What are the intrinsic components of the LOS?
→ Thick circular smooth muscle layers
→ Clasp like semi circular smooth muscle
→ Sling like oblique gastric
What activity do the clasp like muscles have?
→ Myogenic but less ACh responsive
How do the sling-like oblique gastric muscles prevent regurgitation?
→ Works in concert with semicircular smooth muscle
→ Response to cholinergic innervation
Why is reflux common in infants?
→ The angle of His is poorly developed
→ Forms a vertical junction with the stomach
What does the crural diaphragm form?
→ encircles the LOS
→ forms a channel through which the oesophagus enters the abdomen
→ Forms the oesophageal hiatus
What kind of action does the crural diaphragm possess?
→ Pinchcock like
What controls the tone of the LOS?
→ Involvement of cholinergic
→ NANC
What causes the intrinsic sphincters to contract?
→ Acetylcholine
→ SP
What causes the intrinsic sphincters to relax?
→ NO and VIP
What is the upper part of the oesophagus supplied by?
→ Somatic motor neurons of vagus nerves without interruption
→Splanchnic nerves
What is the lower part of the oesophagus innervated by?
→ Visceral motor neurons of vagus nerves with interruptions
How is sensory information integrated?
→ Sensory information is sent to the NTS
→ Integration occurs between NTS, nucleus ambiguus and vaso vagal nucleus
→ Food makes its way down
→ UOS relaxes
→ mediated by NO and VIP
→ Information gets sent to LOS via vagus nerve
→ ACh allows contraction to occur
What are the functions of the oesophagus?
→ Swallowing
→ Conveys food from the pharynx to the stomach
→ Efferent impulses pass to the pharyngeal musculature and the tongue
→ Integration of impulses in the NTS, nucleus ambiguus and DVN
By what impulses is swallowing triggered by?
→ trigeminal
→ glossopharyngeal
→ Vagus
How is swallowing initiated?
1) voluntary
→collect material on tongue and push it backwards into the pharynx
2) Waves of involuntary contraction push material into oesophagus
Where does food move?
→ Mouth
→ Oropharynx
→ Laryngopharynx
→ Oesophagus
What are the reflex responses initiated during swallowing?
→Inhibition of respiration
→ nasopharynx is closed off
→ Closure of the glottis by the epiglottis
→Ring of peristaltic waves behind the material move it towards the stomach
→ Second wave of peristalsis moves the food along