Inferior Pharyngeal Constrictor (Cricopharyngeal Part)
Pharynx · Head & Neck
The cricopharyngeal part is the lower, horizontally fibred component of the inferior pharyngeal constrictor. It arises from the side of the cricoid cartilage and, unlike the other constrictors, does not meet a median raphe posteriorly; instead its fibres form a continuous circular band that encircles the pharyngo-oesophageal junction. This arrangement makes it a true sphincter: it forms the upper oesophageal sphincter, remaining tonically contracted to seal the top of the oesophagus and relaxing to let the bolus pass during swallowing. It is innervated by the vagus nerve (CN X) through the pharyngeal plexus and the recurrent laryngeal nerve. Failure of this muscle to relax, or the weak zone just above it, underlies the formation of a pharyngeal pouch.
Origin, Insertion, Action & Nerve
Origin
Side of the cricoid cartilage
Insertion
Encircles the pharyngo-oesophageal junction (no median raphe)
Action
Acts as the upper oesophageal sphincter; relaxes to allow the bolus to pass
Nerve
Vagus nerve (CN X) via the pharyngeal plexus and recurrent laryngeal nerve
Attachments explained
The Inferior Pharyngeal Constrictor (Cricopharyngeal Part) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Side of the cricoid cartilage
Insertion
Encircles the pharyngo-oesophageal junction (no median raphe)
Action & function
When the Inferior Pharyngeal Constrictor (Cricopharyngeal Part) contracts, it produces the following movements: Acts as the upper oesophageal sphincter; relaxes to allow the bolus to pass.
As part of the Pharynx group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Inferior Pharyngeal Constrictor (Cricopharyngeal Part) receives its nerve supply from the Vagus nerve (CN X) via the pharyngeal plexus and recurrent laryngeal nerve.
Because a muscle can only contract when its nerve is intact, injury to the Vagus nerve can weaken or paralyse the Inferior Pharyngeal Constrictor (Cricopharyngeal Part), impairing the movements it normally produces (acts as the upper oesophageal sphincter). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Inferior Pharyngeal Constrictor (Cricopharyngeal Part) (the OIANS method)
Separate the cricopharyngeal part from every other constrictor by its two defining features: it takes origin from the cricoid cartilage and it has no median raphe, so its fibres run horizontally right around the junction. Those facts explain why it behaves as the upper oesophageal sphincter rather than a simple propulsive constrictor, holding the tube shut until a swallow releases it.
Anchor the clinical logic to remember it: because these fibres act sphincterically and lie just below the oblique thyropharyngeal fibres, incoordination between the two creates the pressure that forms a Zenker diverticulum through Killian's dehiscence. Note its recurrent laryngeal contribution, which links its motor supply to the same nerve that drives the intrinsic laryngeal muscles nearby.
Frequently asked questions
Where is the Inferior Pharyngeal Constrictor (Cricopharyngeal Part) located?
The Inferior Pharyngeal Constrictor (Cricopharyngeal Part) is a muscle of the Pharynx group, located in the Head & Neck.
What is the origin of the Inferior Pharyngeal Constrictor (Cricopharyngeal Part)?
Side of the cricoid cartilage
What is the insertion of the Inferior Pharyngeal Constrictor (Cricopharyngeal Part)?
Encircles the pharyngo-oesophageal junction (no median raphe)
What movements does the Inferior Pharyngeal Constrictor (Cricopharyngeal Part) produce?
Acts as the upper oesophageal sphincter; relaxes to allow the bolus to pass
What nerve supplies the Inferior Pharyngeal Constrictor (Cricopharyngeal Part)?
Vagus nerve (CN X) via the pharyngeal plexus and recurrent laryngeal nerve
Is the Inferior Pharyngeal Constrictor (Cricopharyngeal Part) free to study in OIANS?
The Inferior Pharyngeal Constrictor (Cricopharyngeal Part) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Inferior Pharyngeal Constrictor (Cricopharyngeal Part)
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