Superior pharyngeal constrictor

The superior pharyngeal constrictor is the uppermost of the three pharyngeal constrictor muscles (superior, middle, and inferior). It forms the upper segment of the circular muscular wall of the pharynx, playing a vital role in the initiation of swallowing. By constricting the nasopharyngeal and oropharyngeal lumina, it propels the food bolus downward into the lower pharynx..

Origin

The muscle arises from several distinct areas, which can be described in four parts:

• Pterygopharyngeal part: From the lower third of the posterior margin of the medial pterygoid plate and its hamulus.

• Buccopharyngeal part: From the pterygomandibular raphe, shared with the buccinator muscle.

• Mylopharyngeal part: From the alveolar process of the mandible, just above the posterior end of the mylohyoid line.

• Glossopharyngeal part: By a few fibres from the side of the tongue, blending with the fibres of the palatoglossus and styloglossus muscles.

Insertion

All fibres curve posteriorly and medially to insert into:

• The median pharyngeal raphe, and

• The pharyngeal tubercle of the occipital bone (superior fibres)

Relations

• The superior fibres of superior pharyngeal constrictor muscle arch beneath the Levator veli palatini and the auditory tube.

• The interval between the upper border of the muscle and the base of the skull is filled by the pharyngeal fascia, forming the sinus of Morgagni.

Innervation

Supplied by the pharyngeal branch of the vagus nerve (cranial nerve X) via the pharyngeal plexus, which contains motor fibres originating from the cranial part of the accessory nerve (CN XI).

Action

Constricts the upper part of the pharynx during the early phase of swallowing, thereby preventing reflux of food into the oesophagus.

Clinical correlate

• Vagus nerve lesions may result in weakness or paralysis of the muscle, leading to nasal regurgitation and dysphagia.

• The pterygomandibular raphe serves as an important intraoral landmark for procedures such as the inferior alveolar nerve block during dental anaesthesia.