Pharyngeal Muscles

👉The pharyngeal muscles are a group of muscles that form the pharynx, which is posterior to the oral cavity, determining the shape of its lumen, and affecting its sound properties as the primary resonating cavity.

👉The pharyngeal musculature (involuntary skeletal muscles) function is to push the food bolus into the esophagus.

👉There are two muscular layers of the pharynx: the outer circular layer and the inner longitudinal layer.

👉The outer circular layer includes:

  • Inferior pharyngeal constrictor muscle:
    • Located in the laryngopharynx
    • It has two components:
      • Superior component (thyropharyngeus):
        • Has oblique fibres that attach to the thyroid cartilage.
      • Inferior component (cricopharyngeus):
        • Has horizontal fibres that attach to the cricoid cartilage.
    • Inserts posteriorly into the midline fibrous pharyngeal raphe
  • Middle pharyngeal constrictor muscle:
    • Located in the laryngopharynx
    • Originates from the stylohyoid ligament and the horns of the hyoid bone.
    • Inserts posteriorly into the midline fibrous pharyngeal raphe
  • Superior constrictor muscle:
    • The uppermost pharyngeal constrictor
    • It is located in the oropharynx
    • Originates from the pterygomandibular ligament, alveolar process of mandible and medial pterygoid plate and pterygoid hamulus of the sphenoid bone
    • Inserts posteriorly into to the pharyngeal tubercle of the occiput and the medial fibrous pharyngeal raphe

👉During swallowing, these muscles constrict to propel food bolus downwards (an involuntary process).

👉The inner longitudinal layer includes:

  • Stylopharyngeus muscle:
    • Arises from the styloid process of the temporal bone, inserts into the pharynx
    • Unlike the other pharyngeal muscles:
      • It is innervated by the glossopharyngeal nerve (CN IX)
  • Salpingopharyngeus muscle:
    • Arises from the Eustachian tube, inserts into the pharynx
    • Innervated by the vagus nerve (CN X)
    • In addition to contributing to swallowing:
      • It also opens the Eustachian tube to equalize the pressure in the middle ear
  • Palatopharyngeus muscle:
    • Arises from hard palate of the oral cavity, inserts into the pharynx
    • Innervated by the vagus nerve (CN X)

👉During swallowing, these muscles act to shorten and widen the pharynx.

👉They are innervated by the pharyngeal branch of the Vagus nerve (CN X) with the exception of the stylopharyngeus muscle which is innervated by the glossopharyngeal nerve (CN IX).

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