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The digastric muscle is a small but important muscle in the neck, which assists in the movement of the human jaw. It has two bellies, the anterior and posterior belly, which have different embryological origins and are supplied by different cranial nerves. The digastric muscle can be the source of pain, often causing toothache, jaw pain, throat pain, headaches, and pain in the chin and neck. This pain can be caused by trigger points in the muscle, which can be treated with self-massage and stretching.
| Characteristics | Values |
|---|---|
| Digastric Muscle Location | Below the lower jaw |
| Digastric Muscle Structure | Consists of two muscular bellies: the anterior and the posterior |
| Digastric Muscle Function | Raises the hyoid bone, depresses and retracts the mandible, aiding in jaw opening, chewing, and speech |
| Digastric Muscle Innervation | Anterior belly: mylohyoid nerve (mandibular division of the trigeminal nerve); Posterior belly: facial nerve |
| Digastric Muscle Blood Supply | Anterior belly: inferior alveolar artery; Posterior belly: occipital artery |
| Digastric Muscle Trigger Points | Anterior belly: just behind the midline of the jaw; Posterior belly: between the angle of the jaw and the mastoid process |
| Digastric Muscle Pain Referral | Anterior belly: pain referred to the lower incisors; Posterior belly: pain referred to the upper SCM, under the chin, and occasionally the throat and scalp |
| Digastric Muscle Stretches | For the anterior belly: head tipped back with the mandible protruded; for the posterior belly: head turned to the right to move the mastoid process away from the hyoid bone |
| Digastric Muscle Dysfunction | Tempromandibular joint dysfunction (TMD) may cause pain and dysfunction in the jaw, face, and head |
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What You'll Learn
Trigger points in the posterior digastric muscle
The digastric muscle is a small but important muscle in the neck that belongs to the suprahyoid muscles group. It is a paired muscle that has two bellies, the anterior and posterior belly, which are united by an intermediate rounded tendon. The posterior belly is longer than the anterior belly and arises from the mastoid notch on the inferior surface of the skull.
To palpate the trigger points in the posterior belly, the patient's head is turned to the right to move the mastoid process away from the hyoid bone. The head and neck are extended to tense the anterior belly and tension is increased on the posterior belly by pressing on the hyoid bone down and to the left. The trigger points are then palpated between the angle of the jaw and the mastoid process by applying pressure against the underlying neck structures.
To passively stretch the posterior belly of the digastric muscle, the patient leans their head back against the practitioner in a relaxed position with the teeth nearly approximated. The jaw is closed to stretch the muscle as pressure is applied to palpate trigger points against the underlying soft tissue. Direct external palpation of the posterior digastric muscle is difficult due to the depth of the muscle.
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Tempromandibular joint dysfunction (TMD)
The digastric muscle is one of six key muscles that assist in the movement of the human jaw. It is a small muscle situated under the jaw, with its primary function being to elevate the hyoid bone, a small, horseshoe-shaped bone located between the thyroid cartilage and chin. This action helps to open the mouth and aids in swallowing.
The exact causes of TMD are not fully understood, but it is believed to be multifactorial, requiring a multidisciplinary approach to treatment. General practitioners and dentists are usually the first point of contact, and they can initiate a non-invasive process to manage the condition. In cases of severe pain, ineffective conservative treatment, or a history of trauma to the TMJ, patients should be referred to a specialist for further evaluation and treatment options, such as painkilling injections or surgery.
There are several exercises that can help manage TMD symptoms. One simple exercise is lip puffing, which helps to disengage the teeth and reduce pain and discomfort. Stretching exercises can also improve the range of motion, but they may not always alleviate pain. Manual techniques such as soft tissue mobilisation, joint mobilisation, muscle conditioning, and resistance exercises can also be beneficial.
Additionally, patient education plays a crucial role in managing TMD. Understanding the relationship between muscle hyperactivity and stress can improve patients' behaviour towards the condition and enhance their psychological health. Clinicians can instruct patients to move their mandible within a pain-free range of motion, promoting better psychological health and pain management.
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Dental trauma, bruxism, or stress
The digastric muscle is one of six muscles that assist in the movement of the human jaw. It helps to open the mouth by lowering the mandible and assisting in swallowing. Located under the jaw, the digastric muscle has two bellies: the anterior and the posterior. Each belly has its own trigger point.
Dental trauma, bruxism, and stress can all cause digastric muscle pain. Dental trauma refers to any injury to the teeth or mouth, including the jaw. This can include tooth decay, gum disease, and dental caries. Bruxism, or teeth grinding, is a temporomandibular disorder that can lead to chronic facial pain, including pain in the digastric muscle. Stress can also cause digastric muscle pain, as it can lead to jaw clenching and teeth grinding, which can put pressure on the digastric muscle.
Dental trauma can cause digastric muscle pain due to the close proximity of the teeth and the muscle. Trauma to the teeth, such as a cracked or broken tooth, can put pressure on the digastric muscle and cause pain. Additionally, dental trauma can lead to incorrect swallowing patterns, which can cause facial muscle tension and further contribute to digastric muscle pain.
Bruxism, or teeth grinding, is a common condition that often occurs at night during sleep. It can be caused by stress, anxiety, or certain medications. Bruxism can lead to chronic facial pain, including pain in the digastric muscle. This is because the repetitive clenching and grinding of the teeth can cause the muscles in the jaw, including the digastric muscle, to become tense and inflamed.
Stress can also contribute to digastric muscle pain, even without the presence of bruxism or dental trauma. When stressed, people often clench their jaws and grind their teeth, which can put pressure on the digastric muscle and lead to pain. Additionally, stress can cause the muscles in the body to become tense and inflamed, including the digastric muscle.
To relieve digastric muscle pain caused by dental trauma, bruxism, or stress, there are several treatments available. Pain-relief medications and muscle repair surgery are common approaches. For TMJ disorders, oral splints or dental surgery may be recommended to minimize the impact on the digastric muscle. Physical therapy, such as myofunctional therapy, can also be effective in reducing muscle tension and pain.
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Digastric muscle anatomy and function
The digastric muscle, also known as the digastricus, is a bilaterally paired suprahyoid muscle located under the jaw. The term "digastric" refers to its structure, as it is comprised of two muscular bellies—the anterior belly and the posterior belly—united 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. The tendon connecting the two bellies passes through a fibrous loop that attaches to the hyoid bone, allowing the tendon to slide anteriorly and posteriorly.
The embryological origins of the two bellies differ, resulting in distinct innervation patterns. The anterior belly is derived from the first brachial arch and is innervated by the mandibular nerve (cranial nerve V) or, in some cases, both the mandibular nerve and the facial nerve. It is located closer to the sub-mandibular salivary gland, which is a content of the digastric triangle. The posterior belly, on the other hand, arises from the second brachial arch and is innervated by the facial nerve (cranial nerve VII). It is situated posterior to the parotid gland and adjacent to the sternocleidomastoid muscles, longus colli, and splenius capitis.
The digastric muscle plays a role in depressing the mandible or elevating the hyoid bone. It coordinates with other head and neck muscles during swallowing, chewing, and speech. The muscle's function and attachments are crucial in understanding its potential involvement in various clinical conditions, such as digastric hemangiomas, which may manifest as neck pain.
The digastric muscle also has anatomical variations, particularly in the anterior belly, which exhibits variations in up to 65.8% of the population. These variants include accessory muscle bellies with different origins and insertions, as well as nerve supply variations. However, these variations do not typically produce clinical symptoms.
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Digastric muscle variations
The digastric muscle, also known as the digastricus, is a small but important muscle in the neck. It is involved in any complex jaw action, such as speaking, swallowing, chewing, and breathing. It is also a critical surgical landmark during neck dissections and neck reconstruction procedures.
The digastric muscle has two bellies: the anterior belly and the posterior belly. The two bellies are united by an intermediate tendon, which sometimes penetrates the stylohyoid muscle. The anterior belly is the smaller of the two structures and is located on the lower border of the mandible. It arises from a depression on the inner side of the lower border of the mandible, known as the digastric fossa of the mandible, close to the midline. The posterior belly, on the other hand, is longer than the anterior belly. It arises from the mastoid notch, which is located on the inferior surface of the skull, medial to the mastoid process of the temporal bone.
Numerous structural variations have been observed in the digastric muscle. These variations are primarily in the shape and location of muscle attachment. For example, the anterior belly may be double, or it may have additional slips that pass to the jaw or mylohyoid muscle. In some cases, the anterior belly can be innervated by both the mylohyoid nerve and the facial nerve. The posterior belly may arise partly or entirely from the styloid process of the temporal bone. It may also be connected by a muscle slip to the middle or inferior constrictor.
The digastric muscle can also vary in different species. For example, in orangutans, the posterior digastric attaches to the mandible rather than the hyoid.
It is important to be aware of these variations in the clinical assessment and surgical planning. The digastric muscle variants may be confused with neck masses, and the anatomical variations can be misleading in imaging studies.
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Frequently asked questions
The digastric muscle (also digastricus) is a small muscle situated under the jaw. It has two bellies, the anterior and posterior belly, and is one of six key muscles that assist in the movement of the human jaw.
The most common symptom of digastric muscle pain is tooth pain. However, pain can also be caused by trigger points in the muscle, which can refer pain to the upper part of the SCM, under the chin, and sometimes into the occiput.
To relieve tension in the digastric muscle, place the tips of both thumbs under your chin, one in front of the other, with your chin jutted forward and your head tilted slightly upwards.
One exercise to relieve digastric muscle pain is to place your tongue against the roof of your mouth, gradually increasing the pressure while holding your thumbs firmly against the muscle. Hold for ten seconds and repeat three times.
TMD is a disorder of the temporomandibular joint (TMJ) that affects the muscles and joints of the jaw. Symptoms include pain and dysfunction in the jaw, face, and head. The digastric muscle is one of the muscles involved in TMD.
