The geniohyoid is a small muscle located in the neck, running from the chin to the hyoid bone. It is part of the suprahyoid muscle group and participates in routine actions involving the jaw and throat. Its name reflects its connection between the chin (geno-) and the U-shaped hyoid bone. Its placement underneath the tongue allows it to act on several structures in the neck.
Anatomy and Location of the Geniohyoid
The geniohyoid muscle is a narrow, paired muscle in the anterior neck, just superior to the mylohyoid muscle. It originates from a bony prominence on the inner surface of the mandible called the inferior mental spine. Its fibers travel in a posterior and inferior direction to insert onto the anterior surface of the hyoid bone’s body.
As one of the suprahyoid muscles, the geniohyoid helps form the floor of the oral cavity. The paired muscles lie next to each other, reinforcing this floor. Its nerve supply comes from the first cervical nerve (C1), with nerve fibers traveling alongside the hypoglossal nerve to reach the muscle. This arrangement allows it to influence the hyoid bone, larynx, and mandible.
Primary Functions of the Geniohyoid Muscle
The geniohyoid muscle executes two primary mechanical actions for swallowing and speech. Its main function is to pull the hyoid bone forward and upward, which elevates the hyoid bone and, by extension, the larynx. This elevation is a preparatory action for swallowing, as it helps position the pharynx to receive food.
When the hyoid bone is held in a fixed position by other muscles, the geniohyoid’s role reverses, and it assists in depressing the mandible. This action helps to open the mouth. The muscle’s ability to shorten the floor of the mouth and widen the pharynx further contributes to both swallowing and the production of sound for speech.
Associated Conditions and Pain
Dysfunction or injury to the geniohyoid muscle can lead to conditions related to swallowing and neck comfort. Weakness or poor coordination of this muscle can impair the initial phase of swallowing, a condition known as dysphagia. This difficulty can manifest as a sensation of food being stuck in the throat or requiring extra effort to initiate a swallow.
Tension or strain in the geniohyoid can be a source of pain in the throat, jaw, and anterior neck. Such tightness might result from poor posture, trauma, or overuse. This discomfort can sometimes be associated with symptoms of temporomandibular joint (TMJ) disorders, as the muscle’s function is linked to jaw movement. Persistent pain or issues with swallowing may indicate an underlying injury, such as a muscle strain or tear.