QS Study

The suprahyoid muscles are four muscles located above the hyoid bone in the neck. They all act to elevate the hyoid bone – an action involved in swallowing.

Suprahyoid muscles

  • The digastric muscle.
  • The stylohyoid muscle.
  • The mylohyoid muscle.
  • The geniohyoid muscle.

(1) The digastric muscle – The digastric is comprised of two muscular bellies, which are connected by a tendon.

Nerve supply:

  • Anterior division by the mylohyoid nerve.
  • Posterior division by the facial nerve.

Action: Depresses the mandible and elevates the hyoid bone.

  • Depression of mandible against resistance.
  • Elevation of the hyoid bone.

(2) The stylohyoid muscle – The stylohyoid muscle is a thin muscular strip, which is located superiorly to the posterior belly of the digastric muscle.

Nerve supply: Facial nerve. The stylohyoid muscle grows from the second arch and, hence, it’s supplied by the facial nerve.

Action: Initiates a swallowing action by pulling the hyoid bone in a posterior and superior direction.

  • Pulls the hyoid bone upwards & backward.
  • Fixes the hyoid bone.

suprahyoid muscles 1

Fig: Suprahyoid Muscles – Nerve Supply

(3) The mylohyoid muscle – The mylohyoid is a broad, triangular shaped muscle. It forms the floor of the oral cavity and supports the floor of the mouth.

Nerve supply: Mylohyoid nerve, hence it’s supplied by mylohyoid nerve, a branch of inferior alveolar nerve from mandibular nerve.

Action:

  • Elevates the floor of mouth during 1st stage of deglutition.
  • Depression of the mandible.
  • Elevation of the hyoid bone.

(4) The Geniohyoid muscle – The geniohyoid is located close to the midline of the neck, deep to the mylohyoid muscle.

Nerve supply: 1st cervical nerve by the fibers pass through the hypoglossal nerve.

Actions:

  • Elevates the hyoid bone.
  • Depress the mandible when hyoid is fixed.
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