Three paired constrictor muscles — superior, middle, inferior — arranged like a flowerpot without a base (telescoping/overlapping arrangement).

Each constrictor: arises in front from margins of posterior openings of nasal/oral/laryngeal cavities → passes backward in fan-shaped manner → inserts into median fibrous raphe (extending from pharyngeal tubercle of occipital bone to oesophagus).

Overlapping (from outside): Inferior overlaps middle → middle overlaps superior

Individual Constrictors

Inferior Constrictor — Two Parts

Cricopharyngeus = upper oesophageal sphincter (UOS) — tonically contracted at rest, relaxes only during swallowing

Actions

All three constrictors → constrict pharynx during deglutition — propel food bolus downwards in peristaltic sequence (superior → middle → inferior)

Gaps in Pharyngeal Wall (4 gaps)

Mnemonic (top→bottom): Auditory-Levator / Stylo-Glosso / Internal laryngeal / Recurrent laryngeal

Pharyngeal Plexus

• On posterolateral pharynx over middle constrictor, beneath buccopharyngeal fascia
• Components: pharyngeal branch of vagus (CN X, carrying CN XI cranial root = motor to all pharyngeal muscles except stylopharyngeus), pharyngeal branch of CN IX (sensory), sympathetic from superior cervical ganglion (vasomotor)

Nerve Supply Summary

Longitudinal Muscles of Pharynx (Inner Layer)

Elevate larynx + shorten pharynx during swallowing.

Applied Anatomy

Pharyngeal Pouch (Zenker’s Diverticulum)

• Site: Killian’s dehiscence — potential gap between oblique fibres of thyropharyngeus (above) + transverse fibres of cricopharyngeus (below), posterior wall of inferior constrictor
• Mechanism: neuromuscular incoordination — thyropharyngeus (pharyngeal plexus) contracts while cricopharyngeus (RLN) fails to relax → mucosa + submucosa bulge posteriorly through dehiscence
• Presentation: progressive dysphagia, regurgitation of undigested food, gurgling sounds, neck swelling, halitosis
• Rx: endoscopic or open diverticulotomy + cricopharyngeal myotomy

Deglutition (Swallowing)

• Stage 1 (voluntary/oral): bolus pushed back into oropharynx by tongue
• Stage 2 (pharyngeal, involuntary): nasopharyngeal isthmus closed (soft palate + Passavant’s ridge); laryngeal inlet closed; longitudinal muscles elevate larynx + pharynx; constrictors propel bolus sequentially
• Stage 3 (oesophageal): thyropharyngeus propulsion + cricopharyngeus relaxation → food enters oesophagus

Sinus of Morgagni — gap between pharyngobasilar fascia + upper border of superior constrictor; auditory tube + levator palati enter nasopharynx here; site where nasopharyngeal carcinoma most commonly spreads → occludes auditory tube → conductive hearing loss

Overview

The pharynx has three paired constrictor muscles — superior, middle, and inferior — arranged like a flowerpot without a base, placed one inside the other (telescoping arrangement). Each constrictor:

• Arises in front from the margins of the posterior openings of the nasal, oral, and laryngeal cavities
• Passes backwards in a fan-shaped manner
• Inserts into the median fibrous raphe on the posterior aspect of the pharynx (extending from the pharyngeal tubercle of the occipital bone to the oesophagus)

Overlapping arrangement (from outside): Inferior overlaps middle → Middle overlaps superior

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Individual Constrictors — Origin, Insertion, Nerve Supply

Inferior Constrictor — Two Parts

Cricopharyngeus acts as the upper oesophageal sphincter (UOS) — it remains tonically contracted at rest and relaxes only during swallowing.

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Action

All three constrictors → constrict the pharynx during deglutition (swallowing) — propel the food bolus downwards in sequence (peristaltic wave from above downward).

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Gaps in the Pharyngeal Wall

Four gaps exist in relation to the constrictors, through which structures enter the pharynx:

Mnemonic for gap contents (top to bottom): “Auditory Levator / Stylo Glosso / Internal laryngeal / Recurrent laryngeal”

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Pharyngeal Plexus

Lies on the posterolateral aspect of the pharynx over the middle constrictor, beneath the buccopharyngeal fascia.

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Nerve Supply — Summary

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Longitudinal Muscles of the Pharynx

Three longitudinal muscles form the inner layer of the muscular coat. They elevate the larynx and shorten the pharynx during swallowing.

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Clinical Correlations

Pharyngeal Pouch (Zenker’s Diverticulum)

• Site: Killian’s dehiscence — the potential gap between the oblique fibres of thyropharyngeus (above) and the transverse fibres of cricopharyngeus (below) in the posterior wall of the inferior constrictor
• Mechanism: Neuromuscular incoordination — thyropharyngeus (pharyngeal plexus) contracts while cricopharyngeus (recurrent laryngeal nerve) fails to relax → mucosa and submucosa bulge posteriorly through the dehiscence
• Presentation: Progressive dysphagia, regurgitation of undigested food, gurgling sounds, neck swelling, halitosis
• Treatment: Surgical — endoscopic or open diverticulotomy + cricopharyngeal myotomy

Deglutition (Swallowing) — Role of Constrictors

• Stage 1 (voluntary/oral): Bolus pushed back into oropharynx by tongue
• Stage 2 (pharyngeal — involuntary): Nasopharyngeal isthmus closed by soft palate + Passavant’s ridge; laryngeal inlet closed; longitudinal muscles elevate larynx and pharynx; constrictors propel bolus downward sequentially
• Stage 3 (oesophageal): Thyropharyngeus propulsion + cricopharyngeus relaxation → food enters oesophagus

Sinus of Morgagni

Gap between the pharyngobasilar fascia and the upper border of the superior constrictor through which the auditory tube and levator palati enter the nasopharynx. This is also the site where nasopharyngeal carcinoma most commonly spreads to occlude the auditory tube → causing conductive hearing loss.

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