GENERAL INFORMATION
The digastric muscle is a unique muscle located in the neck, consisting of two bellies: an anterior and a posterior belly. It plays a crucial role in jaw movement and assists in swallowing by elevating the hyoid bone and lowering the mandible. The digastric muscle is part of the suprahyoid muscle group, which helps support the floor of the mouth and stabilise the hyoid bone during speech and swallowing. Its coordinated action is essential for functions such as chewing and speaking.
ORIGIN
- Anterior belly: Originates from the digastric fossa of the mandible.
- Posterior belly: Originates from the mastoid notch of the temporal bone.
INSERTION POINT
The two bellies of the digastric muscle insert into the hyoid bone via an intermediate tendon that connects both bellies, allowing them to work together during jaw and neck movements.
MAJOR ARTERIES
- Facial artery: Supplies blood to the anterior belly of the digastric muscle.
- Occipital artery: Provides blood to the posterior belly, ensuring adequate circulation and nourishment.
NEURAL INNERVATION
- Anterior belly: Innervated by the mylohyoid nerve, a branch of the mandibular division of the trigeminal nerve (cranial nerve V).
- Posterior belly: Innervated by the facial nerve (cranial nerve VII).
TRIGGER POINT
Trigger points in the digastric muscle can cause pain in the lower jaw, under the chin, and in the upper neck. This can result in discomfort when chewing, speaking, or swallowing. Trigger points may also contribute to tension headaches or pain radiating to the ear.
CONCENTRIC FUNCTION
During concentric contraction, the digastric muscle elevates the hyoid bone while simultaneously lowering the mandible. This action helps open the mouth during chewing and speaking, making it essential for daily functions such as eating and talking.
ECCENTRIC FUNCTION
In eccentric contraction, the digastric muscle lengthens as it controls the closing of the jaw. This action helps maintain smooth, controlled jaw movement when chewing or returning the mandible to a resting position after opening.
ISOMETRIC FUNCTION
The digastric muscle can stabilise the jaw and hyoid bone in a fixed position during isometric contraction, maintaining tension while keeping the mouth open or during sustained swallowing.
RELATED MUSCLES – SCIENTIFIC NAMES
- Mylohyoid muscle: Supports the floor of the mouth and assists in jaw movement.
- Stylohyoid muscle: Elevates the hyoid bone, aiding in swallowing.
- Geniohyoid muscle: Assists in depressing the mandible and elevating the hyoid.
- Masseter muscle: Elevates the mandible, contributing to chewing.
ANTAGONIST
- Masseter muscle: Opposes the digastric muscle by elevating the mandible during chewing and closing the mouth.
- Temporalis muscle: Acts as an antagonist by elevating and retracting the jaw.
COMMON INJURIES
- TMJ Dysfunction: Overuse of the digastric muscle can contribute to temporomandibular joint dysfunction, leading to pain, clicking, or difficulty moving the jaw.
- Muscle Strain: Strain on the digastric muscle due to excessive jaw movement or poor posture can result in discomfort and tightness in the lower jaw and neck.
- Tension Headaches: Tightness or trigger points in the digastric muscle can radiate pain to the head, causing tension headaches that affect the jaw and temples.
- Jaw Pain: Overloading the digastric muscle, especially during prolonged chewing or clenching, can lead to jaw pain and discomfort when opening the mouth.
- Neck Pain: Strain or injury to the digastric muscle may cause tension or stiffness in the neck, affecting overall neck mobility and function.
EXERCISES
- Jaw Resistance Exercise: Place your hand under your chin and press lightly as you try to open your mouth. This exercise strengthens the digastric muscle and improves jaw control.
- Chin Tuck Exercise: Gently tuck your chin towards your neck, engaging the digastric muscle while improving neck posture and strengthening the suprahyoid muscles.
- Mouth Opening Exercise: Slowly open your mouth as wide as possible, then close it in a controlled manner. This exercise strengthens the digastric muscle by working through its full range of motion.
- Isometric Jaw Hold: Open your mouth halfway and hold for a few seconds while maintaining tension in the digastric muscle. This exercise enhances muscle endurance and control.
- Neck Flexion with Resistance: Lie on your back and gently press your chin towards your chest while resisting the movement with your hand. This exercise activates the digastric muscle and strengthens the neck.
STRETCHES
- Digastric Stretch: Tilt your head back gently while opening your mouth wide. This stretch helps release tension in the digastric muscle and the surrounding neck muscles.
- Jaw Stretch: Open your mouth as wide as possible and hold for a few seconds, then slowly close it. This stretch helps relieve tightness in the digastric muscle and promotes flexibility.
- Chin-to-Chest Stretch: Gently tuck your chin towards your chest to stretch the back of the neck, relieving tension in the digastric muscle and improving overall neck flexibility.
- Neck Side Stretch: Tilt your head towards one shoulder and hold for 20-30 seconds to release tightness in the digastric muscle and surrounding muscles.
- Tongue Stretch: Stick your tongue out as far as possible and hold for a few seconds. This movement helps stretch the muscles of the mouth and jaw, including the digastric, improving mobility and reducing tension.