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Middle pharyngeal constrictor muscle

The middle pharyngeal constrictor is the intermediate muscle of the three pharyngeal constrictors and forms a substantial portion of the oropharyngeal lateral and posterior wall. It is fan-shaped, arising broadly from the hyoid bone and stylohyoid ligament and sweeping posteriorly to insert into the pharyngeal raphe.

It plays a crucial role in the pharyngeal phase of swallowing, contracting sequentially after the superior pharyngeal constrictor to propel the food bolus downward. It also forms an important anatomical landmark separating adjacent neurovascular structures and interfacing with the suprahyoid and infrahyoid musculature.

Synonyms

  • Constrictor pharyngis medius

  • Middle constrictor muscle

Origin, Course, and Insertion

Origin:

  • Greater horn of hyoid bone

  • Lesser horn of hyoid bone

  • Stylohyoid ligament

Course:

  • Fibers fan posteriorly and medially, narrowing as they approach the midline

  • Forms the middle portion of the pharyngeal wall at the level of the oropharynx

Insertion:

  • Pharyngeal raphe along the midline posterior pharyngeal wall

Relations

  • Superiorly: Superior pharyngeal constrictor muscle

  • Inferiorly: Inferior pharyngeal constrictor muscle

  • Anteriorly: Hyoid bone, hyoglossus muscle, and lingual neurovascular structures

  • Posteriorly: Retropharyngeal space and prevertebral fascia

  • Laterally: Carotid space, including carotid artery and internal jugular vein (not described in detail per instructions)

Function

  • Contracts during the second phase of swallowing to propel the bolus toward the laryngopharynx

  • Ensures coordinated peristaltic movement of the pharyngeal wall

  • Contributes to structural support of the oropharyngeal cavity

MRI Appearance

T1-weighted images:

  • Muscle shows intermediate signal intensity, slightly darker than surrounding fat

  • Well-defined along the lateral and posterior walls of the oropharynx

  • Clear separation from parapharyngeal fat and mucosal lining

T2-weighted images:

  • Normal muscle demonstrates intermediate-to-low signal intensity

  • Oropharyngeal mucosa appears brighter than muscle

  • Airway lumen appears dark, allowing sharp muscular delineation

STIR:

  • Muscle appears intermediate-to-dark signal with effective fat suppression

  • Highlights muscle contour against adjacent bright fat planes

T1 Fat-Saturated Post-Contrast:

  • Displays mild, uniform enhancement throughout the muscle

  • Mucosal layer enhances more intensely compared to deeper muscle fibers

  • Posterior pharyngeal wall shows smooth continuous enhancement

CT Appearance

Non-Contrast CT:

  • Appears as soft-tissue density forming the mid-level pharyngeal wall

  • Separated from parapharyngeal fat by smooth soft-tissue borders

  • Hyoid bone provides a prominent anterior landmark

Post-Contrast CT:

  • Shows subtle, homogeneous muscular enhancement

  • Pharyngeal mucosa enhances more vividly

  • Provides clear visualization of symmetric pharyngeal wall thickness

MRI image

Middle pharyngeal constrictor muscle