The structure indicated is the hyoglossus muscle of the tongue.

The hyoglossus muscle is one of the extrinsic muscles of the tongue. The muscles involved with the tongue consist of intrinsic muscles which lie within the tongue itself, and the extrinsic muscles which attach to the tongue and are responsible for depression, elevation, protraction and retraction of the tongue.

There are four sets of extrinsic tongue muscles:

1. Genioglossus
2. Hyoglossus
3. Palatoglossus
4. Styloglossus

Origin: Greater horn and body of hyoid bone

Insertion: Lateral aspect of tongue

Action: Depression and retraction of tongue

Innervation:  Hypoglossal nerve (cranial nerve XII)

Learn all about the anatomy of the cranial nerves and the extrinsic muscles of the tongue and hyoid bone.