Digastric Muscle: Definition, Types, and Examples

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Digastric Muscle Definition

One of the rare muscles with distinct muscular bellies is the digastric muscle. An intermediate rounded tendon that runs through the hyoid bone separates these two sections of the digastric muscle. Each side of the jaw has a digastric muscle that connects the jaw to the bottom section of the skull through the hyoid.

Pulley actions on the jaw are possible because of this intricate system, which works in tandem with the other jaw muscles to accomplish complicated motions like eating, speaking, and breathing. Because of the intricate structure of the nerves connected with the digastric muscle, pain associated with it is frequently misdirected.

Digastric Muscle Structure

The symphysis menti is where the digastric muscle attaches to the mandible, or jaw bone. This tiny ridge runs through the centre of the jaw and links to a number of muscles, including the left and right digastric muscles.

The muscle’s anterior belly goes from the mouth to the tendon that connects the two bellies. The hyoid bone is attached to the tendon, which permits tension to be transmitted from either belly along the muscle’s course. This intermediate tendon is connected to the temporal bone of the skull by the muscle’s posterior belly.

This bone is located near the base of the skull and contains a tiny slot where the posterior belly attaches, known as the mastoid notch. The trigeminal nerve serves the anterior belly of the muscle, whereas the facial nerve serves the posterior belly. In the picture below, the digastric muscle is emphasised.

Digastric Muscle Function

The digastric muscle, unlike other muscles, may contract in two halves. Because the muscles’ bellies are fed by distinct nerves, they can contract independently. While the specific mechanisms of the face and jaw muscles are complex, the digastric muscle acts as a tension pulley to create stress on the jaw in various directions.

The digastric muscles link to the lower cranium through a pulley system at the hyoid bone on the left and right sides, respectively. This implies that when this muscle contracts, it can cause the mouth to open and move from side to side.

As a result, the digastric muscle is in charge of activities including speaking, chewing, swallowing, and breathing. Any complicated jaw motion will almost certainly include the muscle in some way.

Digastric Muscle Pain

When patients have jaw, throat, tooth, or general face pain, the digastric muscle is frequently identified as the cause. The muscle is prone to tense up because it has two halves that are innervated by distinct branches of cranial nerves and operate a complicated tendon pulley.

Unfortunately, tension in the anterior belly of the muscle does not generate the same feeling as tension in the posterior belly. The facial nerve is linked to the posterior abdominal button. The trigeminal nerve, which links to distinct regions of the face and jaw rather than the facial nerve, is linked to the anterior abdomen.

As a result, any stress in any portion of the muscle can cause discomfort to spread across the face and jaw. Even if the discomfort may not appear to be coming from the digastric muscle, relaxing the muscle with very basic jaw motions and gentle massage should relieve the tension and lessen the pain.

Digastric Muscle Citations
  •  Absent Posterior Belly of Digastric Muscle. Laryngoscope . 2021 Jul;131(7):1501-1502.
  • Anatomy, Head and Neck, Digastric Muscle. PMID: 31335072
  • Anatomy and variations of digastric muscle. Anat Cell Biol . 2019 Mar;52(1):1-11.
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