Infrahyoid muscles

INFRAHYOID MUSCLES


INTRODUCTION:

  • The infrahyoid muscles (strap muscles) are a group of four pairs of muscles in the anterior (frontal) part of the neck.
  • The four infrahyoid muscles are; the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles.
  • The infrahyoid muscles either originate from or insert on to the hyoid bone.
  • Omohyoid is a digastric muscle.
  • Omohyoid is an important landmark for anterior & posterior triangle of neck .
  • The term infrahyoid refers to the region below the hyoid bone, while the term strap muscles refers to the long and flat muscle shapes which resembles a strap. 
  • The stylopharyngeus muscle is considered by many to be one of the strap muscles, but is not an infrahyoid muscle.
Muscle Origin Insertion Innervation
Sternohyoid Posterior surface of manubrium sterni, adjoining parts of clavicle and the posterior sternoclavicular ligament Medial part of lower border of hyoid bone Ansa cervicalis
Sternothyroid Posterior surface of manubrium sterni and adjoining part of first costal cartilage Oblique line of thyroid cartilage Ansa cervicalis
Thyrohyoid Oblique line of thyroid cartilage Lower border of the body and the greater cornu of the hyoid bone Cervical spinal nerve 1 via the hypoglossal nerve
Omohyoid (superior belly) Intermediate tendon Hyoid bone Superior root of ansa cervicalis (C1)
Omohyoid (inferior belly) Superior border of scapula Intermediate tendon Ansa cervicalis (C1-C3)

INNERVATION:

  • All of the infrahyoid muscles are innervated by the ansa cervicalis from the cervical plexus (C1-C3) except the thyrohyoid muscle, which is innervated by fibers only from the first cervical spinal nerve travelling with the hypoglossal nerve.

ACTION:

  • The infrahyoid muscles function to depress the hyoid bone and larynx during swallowing and speech.
Exam Question
 
  • Sternothyroid & thyrohyoid are Attached to oblique line of thyroid cartilage.
  • Omohyoid is a digastric muscle.
  • Omohyoid is an important landmark for Anterior & posterior triangle.
  • Sternthyroid, sternohyoid & omohyoid are the muscles innervated my ansa cervicalis.
  • All infrahyoid muscles depresses larynx.
Don’t Forget to Solve all the previous Year Question asked on INFRAHYOID MUSCLES

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