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The digastric muscle is a small but important muscle in the neck, consisting of two muscular bellies: the anterior and posterior belly, which are united by an intermediate tendon. The muscle is involved in multiple actions, including depressing the mandible and elevating the hyoid bone. The digastric muscle is present in a variety of animals, with specific attachment sites varying between species. In humans, the digastric muscle divides the anterior triangle of the neck into four smaller triangles.
| Characteristics | Values |
|---|---|
| Number of Muscles | 2 |
| Muscle Type | Suprahyoid |
| Muscle Bellies | 2 (Anterior and Posterior) |
| Anterior Belly Origin | Digastric fossa of mandible |
| Posterior Belly Origin | Mastoid notch of temporal bone |
| Innervation | Mandibular nerve (Anterior Belly), Facial nerve (Posterior Belly) |
| Function | Depresses the mandible, Elevates the hyoid bone, Stabilises the hyoid during swallowing, Raises the tongue base, Aids in head extension |
| Attachments | Hyoid bone, Mandible |
| Related Muscles | Mylohyoid, Geniohyoid, Stylohyoid, Platysma |
| Blood Supply | Vertebral artery, Deep descending branch of the occipital artery |
| Surgical Use | Surgical landmark in neck dissections, Valuable in neck reconstruction |
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What You'll Learn
- The digastric muscle has two bellies: the anterior and posterior
- The muscle is involved in depressing the mandible and elevating the hyoid bone
- The muscle's embryological origins differ between the anterior and posterior bellies
- The digastric muscle has trigger points that can cause pain in various areas
- The muscle is present in a variety of animals, with variations in attachment sites
The digastric muscle has two bellies: the anterior and posterior
The digastric muscle, also known as the digastricus, is a bilaterally paired suprahyoid muscle located under the jaw. Its name is derived from the Greek word "dis", meaning double or twofold, and the Latin "gaster", meaning belly. This name accurately describes the muscle's composition, as it is indeed composed of two bellies: the anterior and posterior.
The anterior belly of the digastric muscle originates from the digastric fossa of the mandible, near the midline. It is innervated by the inferior alveolar nerve, a branch of the mandibular nerve (CN V), which is derived from the trigeminal nerve. The anterior belly is also sometimes innervated by the facial nerve. It can be palpated with the neck extended and the head tilted back, and it is stretched by tipping the head back and protruding the mandible in a nearly closed position.
The posterior belly of the digastric muscle originates from the mastoid notch of the temporal bone, located on the inferior surface of the skull. It is innervated by the digastric branch of the facial nerve (CN VII). The posterior belly can be palpated between the angle of the jaw and the mastoid process, and it is stretched by turning the head to move the mastoid process away from the hyoid bone.
The two bellies of the digastric muscle unite to form the intermediate tendon, which attaches to the hyoid bone. The tendon typically pierces the stylohyoid muscle but may lean superiorly or laterally to it. The digastric muscle acts to depress the mandible and elevate the hyoid bone, and it coordinates with other head and neck muscles during swallowing, chewing, and speech.
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The muscle is involved in depressing the mandible and elevating the hyoid bone
The digastric muscle, also known as the digastricus, is a suprahyoid muscle located under the jaw. It is a paired muscle, with each pair consisting of two parts or 'bellies': the anterior belly and the posterior belly. The anterior belly is derived from the first brachial arch, while the posterior belly is derived from the second brachial arch.
The anterior belly of the digastric muscle originates from the digastric fossa of the mandible, near the midline. It is innervated by the mandibular nerve (CN V) or, in some cases, by both the mandibular nerve and the facial nerve. The posterior belly originates at the medial surface of the mastoid notch of the temporal bone. It is innervated by the facial nerve (CN VII). The two bellies are united by an intermediate tendon, which attaches to the hyoid bone.
The digastric muscle is involved in depressing the mandible and elevating the hyoid bone. This action is important for jaw opening, chewing, and speech. During swallowing, the anterior belly of the digastric muscle helps to stabilise the hyoid bone, which protects the airway while eating.
The degree of mouth opening during normal speaking is a factor that influences the resonance characteristics of the supralaryngeal tract. The digastric muscle is one of the jaw-opener muscles, along with the mylohyoideus, pterygoideus lateralis, and geniohyoideus. The jaw-closer muscles include the temporalis, masseter, and pterygoideus medialis.
The digastric muscle can be palpated in the supine position. To palpate the trigger points in the anterior belly, the neck is extended and the head is tilted back. For the posterior belly, the trigger points are palpated between the angle of the jaw and the mastoid process by applying pressure against the underlying neck structures.
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The muscle's embryological origins differ between the anterior and posterior bellies
The digastric muscle is a bilaterally paired suprahyoid muscle located under the jaw, named for its two 'bellies': the anterior belly and the posterior belly. These two bellies are united by an intermediate tendon, which attaches to the hyoid bone. The muscle gets its name from the Greek word "dis", meaning double or twofold, and the Latin "gaster", meaning belly.
The embryological origins of the two bellies differ. The anterior belly is derived from the first brachial arch, while the posterior belly is derived from the second brachial arch. Consequently, the bellies are innervated differently. The anterior belly is innervated by the mandibular nerve (cranial nerve V), and the posterior belly is innervated by the facial nerve (cranial nerve VII). The anterior belly receives motor innervation from the mylohyoid nerve, a branch of the inferior alveolar nerve, which is itself a branch of the mandibular division of the trigeminal nerve (CN V3). The posterior belly is supplied by the digastric branch of the facial nerve.
The anterior belly originates from the digastric fossa of the mandible's lower border, near the midline close to the mandibular symphysis (symphysis menti). It extends inferoposteriorly from its origin toward the intermediate tendon. The posterior belly originates at the medial surface of the mastoid notch of the temporal bone. It travels anteroinferiorly towards the hyoid bone, piercing the stylohyoid muscle before attaching to the intermediate tendon of the digastric muscle.
The digastric muscle may act to depress the mandible or elevate the hyoid bone. The muscle divides the anterior triangle of the neck into four smaller triangles: the submandibular triangle (digastric triangle), the carotid triangle, the submental triangle (suprahyoid triangle), and the inferior carotid triangle (muscular triangle).
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The digastric muscle has trigger points that can cause pain in various areas
The digastric muscle, also known as the digastricus, is a small yet important muscle in the neck. It is comprised of two parts or bellies—anterior and posterior—that unite as an intermediate tendon above the hyoid bone. The digastric muscle is involved in opening the jaw and mouth.
The digastric muscle can develop trigger points due to various factors, including teeth grinding, whiplash, and breathing through the mouth for extended periods. These trigger points can cause pain in various areas, including the throat, jaw, ear, and tongue. In the anterior compartment, trigger points often result in toothaches of the lower middle incisors, while the posterior compartment may refer pain over the mastoid process and occasionally to the throat under the chin.
Furthermore, tensions and trigger points in the digastric muscle can lead to a range of ailments, such as earache and difficulties in swallowing. The activation of trigger points can also cause increased sensitivity along the area below the mandible.
It is important to note that direct external palpation of the posterior digastric muscle can be challenging due to its depth. To examine the anterior digastric muscle, healthcare professionals identify the lateral margins of the hyoid before palpating the inferior surface of the mandible by placing their thumbs on either side of the midline.
By understanding the trigger points and tensions associated with the digastric muscle, individuals can employ self-massage techniques to relieve these issues and alleviate pain in the affected areas.
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The muscle is present in a variety of animals, with variations in attachment sites
The digastric muscle is present in a variety of animals, with variations in attachment sites. The muscle is named digastric as it has two 'bellies'—the anterior and posterior bellies, joined by an intermediate tendon. The posterior belly is attached to the mastoid notch of the temporal bone, while the anterior belly is attached to the digastric fossa of the mandible.
In orangutans, for example, the posterior digastric attaches to the mandible rather than the hyoid. The digastric muscle is part of the suprahyoid group of muscles, which also includes the mylohyoid, geniohyoid, and stylohyoid muscles. These muscles are found superior to the hyoid bone and, along with adjacent tissue, form the floor of the mouth.
The digastric muscle is a small but important muscle in the neck, and it can be divided into four triangles: the submandibular triangle (digastric triangle), the carotid triangle, the submental triangle (suprahyoid triangle), and the inferior carotid triangle (muscular triangle). The muscle's bellies have different embryological origins, with the anterior belly derived from the first brachial arch and the posterior belly from the second brachial arch. Consequently, they differ in their innervation, with the anterior belly innervated via CN V and the posterior belly via CN VII.
The digastric muscle plays a role in depressing the mandible or elevating the hyoid bone. It is also involved in rotating the head and neck when muscles on only one side of the neck are used.
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Frequently asked questions
The digastric muscle is a bilaterally paired suprahyoid muscle located under the jaw. It consists of two muscular bellies, the anterior and posterior belly, which are connected by an intermediate tendon.
The digastric muscle assists in mandible movement, helping to depress the mandible and elevate the hyoid bone.
The anterior belly is derived from the first brachial arch (or pharyngeal arch) and is innervated by the trigeminal nerve (CN V). The posterior belly is derived from the second brachial arch (or pharyngeal arch) and is innervated by the facial nerve (CN VII).
