Digastric Muscle Anatomy

The digastric muscle has two bellies, joined by an intermediate tendon that descends toward its insertion on the hyoid bone. the digastric muscles are critical surgical landmarks during neck dissections and are valuable components of neck reconstruction procedures.

The Digastric pronounced as (di·​gas·​tric), it means of, relating to, or being either of a pair of muscles that depress the lower jaw and raise the hyoid bone during swallowing. Or having two bellies separated by a median tendon.

Digastric Muscle Anatomy

The digastric muscle exhibits a unique anatomical configuration consisting of two distinct bellies connected by an intermediate tendon.

The anterior belly of the digastric muscle originates from the digastric fossa of the mandible, near the midline. This anterior component demonstrates a different embryological origin and innervation pattern compared to its posterior counterpart. The posterior belly emerges from the mastoid notch of the temporal bone. These two muscular components unite via an intermediate tendon that passes through a fibrous sling attached to the hyoid bone, creating a sophisticated pulley-like mechanism.

See Also: Temporomandibular Joint Anatomy

The anterior belly receives its neural supply from the mylohyoid nerve, a branch of the inferior alveolar nerve (V3). In contrast, the posterior belly is innervated by the digastric branch of the facial nerve (CN VII). This distinct innervation pattern reflects the muscle’s complex embryological development, with the anterior belly deriving from the first branchial arch and the posterior belly originating from the second branchial arch.

The digastric muscle’s primary functions include mandibular depression and hyoid bone elevation. During deglutition, the muscle works synergistically with other suprahyoid muscles to facilitate the superior and anterior movement of the hyoid bone. This action is crucial for proper swallowing mechanics and airway protection. When the hyoid bone is fixed, bilateral contraction of the digastric muscle assists in opening the mouth, particularly important in procedures requiring mandibular depression.

Clinical Significance

In cases of Eagle syndrome, the elongated styloid process may irritate the posterior belly, leading to cervical pain. Additionally, the digastric muscle serves as an important surgical landmark during procedures such as submandibular gland excision and anterior neck dissection. Dysfunction of the digastric muscle may contribute to various clinical conditions, including deglutition disorders and temporomandibular joint dysfunction.

Surgeons operating in the submandibular triangle must maintain awareness of the digastric muscle’s position and its relationships to vital structures. The intermediate tendon of the digastric muscle serves as a reliable landmark for identifying the hypoglossal nerve, which typically crosses deep to this tendon. Anatomical variations in the muscle’s attachment points and belly configurations have been reported and should be considered during surgical planning.

References & More

1. “Digastric.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/digastric. Accessed 8 Nov. 2024.
2. Tranchito EN, Bordoni B. Anatomy, Head and Neck, Digastric Muscle. [Updated 2024 Jan 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed