Thyrohyoid muscle

The thyrohyoid muscle is a small skeletal muscle of the neck. Above, it attaches onto the greater cornu of the hyoid bone; below, it attaches onto the oblique line of the thyroid cartilage. It is innervated by fibres derived from the cervical spinal nerve 1 that run with the hypoglossal nerve (CN XII) to reach this muscle. The thyrohyoid muscle depresses the hyoid bone and elevates the larynx during swallowing. By controlling the position and shape of the larynx, it aids in making sound.

Structure
The thyrohyoid muscle is a small,  broad and short muscle.  It is quadrilateral in shape.  It may be considered a superior-ward continuation of sternothyroid muscle. 

It belongs to the infrahyoid muscles group and the outer laryngeal muscle group. 

Attachments
Its superior attachment  is the inferior border  of the greater cornu of the hyoid bone   and adjacent portions of the body of hyoid bone. 

Its inferior attachment  is the oblique line of the thyroid cartilage (alongside the sternothyroid muscle ).  

Innervation
The thyrohyoid muscle is innervated (along with the geniohyoid muscle  ) by a branch of the cervical plexus   - the nerve to thyrohyoid muscle (thyrohyoid branch of ansa cervicalis) - which is formed by fibres of the cervical spinal nerve 1 (C1)   (and - according to some sources - cervical spinal nerve 2 as well  ) that join and travel with the hypoglossal nerve (CN XII)  before splitting away from it   distal to the superior root of ansa cervicalis.   The thyrohyoid muscle is the only infrahyoid muscle that is not innervated via the ansa cervicalis.

Blood supply
The muscle is provided with arterial blood by branches of the superior thyroid artery, and of the lingual artery.

Relations
The thyrohyoid muscle forms the inferior boundary of the carotid triangle. It is situated deep to (beneath) the (depending upon the source) superior portion of /superior belly of  the sternohyoid muscle,  and the superior portion of  the omohyoid muscle.  

Function
The thyrohyoid muscle depresses and fixates the hyoid bone. It elevates the larynx during swallowing.  By controlling the position and shape of the larynx, it aids in making sound.