Human Anatomy - Kotsan I. Ya. 2009

Muscles and fasciae of the neck
Superficial muscles of the neck
Suprahyoid muscles

The suprahyoid Muscles include the digastric, stylohyoid, mylohyoid, and geniohyoid muscles.

The digastric Muscle (m. digastricus) has two bellies: an anterior belly (venter anterior) and a posterior belly (venter posterior). It originates from the mastoid notch of the Temporal bone and inserts into the digastric fossa of the Mandible. The bellies are connected by a well-defined intermediate tendon that passes above the Hyoid bone and is attached to it by a ligament forming a pulley. The anterior and posterior bellies of the digastric muscle delimit the submandibular triangle inferiorly. Function: when the hyoid bone is fixed, the muscle depresses the mandible; when the mandible is fixed, it elevates the hyoid bone and Larynx.

Innervation: the posterior belly is innervated by the Facial Nerve (VII), and the anterior belly by the mylohyoid nerve (a branch of the Trigeminal nerve).

The stylohyoid muscle (m. stylohyoideus) originates from the styloid process of the temporal bone, runs downward and forward, and inserts into the body of the hyoid bone. Near its insertion site, the stylohyoid muscle is pierced by the intermediate tendon of the digastric muscle. Function: pulls the hyoid bone upward and backward.

Innervation: facial nerve (VII).

The mylohyoid muscle (m. mylohyoideus) is a broad, flat muscle originating from the mylohyoid line on the inner surface of the mandible. The muscle fibers run backward, downward, and medially. The anterior and middle fibers

fuse with the fibers of the contralateral muscle to form a tendinous raphe along the midline, while the posterior fibers attach to the body of the hyoid bone. Function: elevates the hyoid bone along with the larynx, and depresses the mandible when the hyoid bone is fixed. The right and left mylohyoid muscles form a muscular plate that closes the space between the mandible and the hyoid bone, creating the floor of the Oral Cavity, known as the oral Diaphragm.

Innervation: mylohyoid nerve (from the trigeminal nerve).

The geniohyoid muscle (m. geniohyoideus) is located lateral to the midline directly on the upper surface of the mylohyoid muscle. It originates from the mental spine of the mandible and inserts into the body of the hyoid bone. Function: elevates the hyoid bone along with the larynx, and depresses the mandible when the hyoid bone is fixed.

Innervation: Cervical plexus (C_I—C_II).