Infrahyiod muscles

INFRAHYOID MUSCLES

Sternohyoid Sternothyroid Thyrohyoid Omohyoid

1 Sternohyoid

Proximal Attachment

  • Posterior surface of manubrium sterni.
  • Adjoining parts of the clavicle and the posterior sternoclavicular ligament.

Distal Attachment

  • Lower border of the body of hyoid bone.

Nerve Supply

  • Ansa cervicalis (C1–C3).

Action

  • Depresses the hyoid bone following its elevation during:
    • Swallowing.
    • Vocal movements.

2 Sternothyroid

Lies deep to the sternohyoid.

Proximal Attachment

  • Posterior surface of manubrium sterni.
  • Adjoining part of 1st costal cartilage.

Distal Attachment

  • Oblique line on the lamina of the thyroid cartilage.

Nerve Supply

  • Ansa cervicalis (C1–C3).

Action

  • Depresses the larynx after it has been elevated during:
    • Swallowing.
    • Vocal movements.

3 Thyrohyoid

Lies deep to the sternohyoid.

Proximal Attachment

  • Oblique line of thyroid cartilage.

Distal Attachment

  • Lower border of the body and greater cornua of hyoid bone.

Nerve Supply

  • C1 through hypoglossal nerve.

Actions

  1. Depresses the hyoid bone.
  2. Elevates the larynx when the hyoid is fixed by the suprahyoid muscles.

4 Omohyoid

Parts

  • Inferior belly
  • Common tendon
  • Superior belly
  • Arises by the inferior belly.
  • Is inserted through the superior belly.

Proximal Attachment

  • Upper border of scapula near the suprascapular notch.
  • Adjoining part of suprascapular ligament.

Distal Attachment

  • Lower border of the body of hyoid bone, lateral to the sternohyoid.
  • The central tendon lies on the internal jugular vein at the level of the cricoid cartilage.
  • It is bound to the clavicle by a fascial pulley.

Nerve Supply

  • Superior belly → superior root of ansa cervicalis.
  • Inferior belly → inferior root of ansa cervicalis.

Action

  • Depresses the hyoid bone following its elevation during:
    • Swallowing.
    • Vocal movements.