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Infrahyoid muscles

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Anatomy

The infrahyoid muscles are a group of four muscles under the hyoid bone attaching to the sternum, larynx and scapula.

Omohyoid Muscle

The omohyoid muscle is divided into a superior and inferior belly. The inferior belly begins at the superior border of scapula, ascends craniomedially and merges into an intermediate tendon at the height of the lateral cervical region. This tendon is connected to the carotid sheath which surrounds the neurovascular bundle (including the common carotid artery, internal jugular vein and vagus nerve). Distally the muscle attaches to the body of hyoid.

Sternothyroid Muscle

The sternothyroid muscle originates from the dorsal surface of the manubrium and inserts on the oblique line of thyroid cartilage. That is why the sternothyroid is the only hyoid muscle that does not directly attach to the hyoid bone. The sternothyroid lies in close relation to the capsule of the thyroid gland.

Thyrohyoid Muscle

The thyrohyoid muscle constitutes the continuation of the sternothyroid, beginning at the oblique line of thyroid cartilage and inserting on the body of hyoid and greater cornu.

Sternohyoid Muscle

The sternohyoid muscle has its origin at the dorsal surface of manubrium and the sternoclavicular joint and its insertion on the body of hyoid. The sternohyoid is the most superficial of all the infrahyoid muscles.

Recommended video: Infrahyoid muscles
Origins, insertions, innervation and functions of the infrahyoid muscles.

Innervation

All four infrahyoid muscles are supplied by the deep ansa cervicalis (C1-C3), which arises from the cervical plexus. The thyrohyoid receives additional supply through branches of the superior root of ansa cervicalis accompanied by the hypoglossal nerve.

Function

The infrahyoid muscles are responsible for the positioning of the hyoid bone along with the suprahyoid muscles. They play an active role in swallowing and the movement of the larynx. More specifically, all infrahyoid muscles (except the sternothyroid) depress the hyoid. The sternothyroid depresses the larynx whereas the thyrohyoid elevates it (when the hyoid bone is fixed). The omohyoid has an additional function due to its attachment to the carotid sheath: by pulling the sheath, it maintains a low pressure in the internal jugular vein, this way increasing the blood return from the head to the superior vena cava.

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Show references

References:

  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1st edition, Urban & Fischer Verlag/Elsevier (2008), p. 185-186
  • W. Platzer: Taschenatlas Anatomie – Band 1 – Bewegungsapparat, 10th edition, Thieme Verlag (2009), p. 326-327
  • G. Boeck/U. Bommas-Ebert/T. Brandenburger et al.: Prüfungswissen Physikum, Thieme Verlag (2009), p. 242
  • R. Gautschi: Manuelle Triggerpunkt-Therapie, 2nd edition, Thieme Verlag (2013), p. 246-247
  • J. Siewert, M. Allgöwer: Chirurgie, 7th edition, Springer-Verlag (2001), p. 478
  • C. Kerawala/M. Heliotos: Prevention of complications in neck dissection, Head and Neck Oncology (2009), 1:35

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