Thyrohyoid m

One of the infrahyoid muscles (or strap muscles) of the neck.  The thyrohyoid may appear to be part of the sternothyroid, but it is a separate muscle.  It attaches to the thyroid cartilage and the hyoid bone (hence the name), and depending on the state of other muscles it may elevate the thyroid cartilage, depress the hyoid, or stabilize either of those structures.  Innervation is by the ansa cervicalis.  

Deep view of the infrahyoid muscles, the sternohyoid has been removed.