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    Related Topics

    From Musculoskeletal System

    Pectoralis Major
    Chest muscle responsible for shoulder movement.
    Occipital Bone
    Bone forming the back and base of the skull.
    Nasal Bones
    Bones forming the bridge of the nose.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Sternum
    Breastbone located in the center of the chest.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Radius
    Forearm bone on the thumb side.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Skull
    Bony structure of the head that encases the brain.
    Patella
    Knee cap, protecting the knee joint.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Pivot Joints
    e.g., atlanto-axial joint
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.

    Masseter

    Reviewed by our medical team

    Muscle that elevates the mandible.

    1. Overview

    The masseter is one of the main muscles of mastication and is among the strongest muscles in the human body relative to its size. Located in the lateral jaw region, it plays a critical role in chewing by elevating the mandible (lower jaw). The masseter works in coordination with the temporalis, medial pterygoid, and lateral pterygoid muscles to facilitate complex mandibular movements.

    2. Location

    The masseter is located on the lateral aspect of the face and jaw:

    • Superficially: Lies just beneath the skin and subcutaneous tissue over the posterior cheek.

    • Anteriorly: Bordered by the buccinator muscle and parotid duct.

    • Posteriorly: Lies near the parotid gland and the mandibular ramus.

    • Deep to: The platysma and skin.

    3. Structure

    The masseter is a thick, quadrangular muscle composed of superficial and deep parts:

    • Origin:

      • Superficial part: Zygomatic process of the maxilla and lower border of the anterior two-thirds of the zygomatic arch.

      • Deep part: Posterior third of the zygomatic arch and deep surface of the arch.

    • Insertion:

      • Superficial fibers: Angle and lower lateral surface of the ramus of the mandible.

      • Deep fibers: Upper half of the ramus and the coronoid process of the mandible.

    • Innervation: Mandibular division (V3) of the trigeminal nerve via the masseteric nerve.

    • Blood supply: Masseteric artery (a branch of the maxillary artery).

    4. Function

    The primary actions of the masseter include:

    • Elevation of the mandible: Closes the jaw during mastication (chewing).

    • Protrusion: The superficial part assists in moving the jaw forward.

    • Stabilization: Helps maintain tension in the jaw during clenching or holding objects between the teeth.

    5. Physiological role(s)

    Beyond its role in movement, the masseter contributes to:

    • Mastication efficiency: Provides significant bite force, enabling effective food breakdown for digestion.

    • Facial contouring: Defines the angle of the jaw and contributes to facial shape and aesthetics.

    • Speech and articulation: Stabilizes the mandible during speech and phonation.

    • Protective tension: Activates during reflex jaw closure to prevent damage from foreign objects or trauma.

    6. Clinical Significance

    The masseter is frequently involved in dental, musculoskeletal, and aesthetic conditions:

    • Temporomandibular joint disorders (TMD):

      • Masseter hyperactivity or spasm can contribute to jaw pain, clicking, and restricted movement.

    • Bruxism (teeth grinding):

      • Involuntary clenching or grinding of teeth, especially at night, can lead to masseter hypertrophy and muscle fatigue.

    • Masseteric hypertrophy:

      • Can result in a square jaw appearance; often seen in chronic bruxism or in athletes who use jaw muscles intensively.

      • Botulinum toxin (Botox) is sometimes used to reduce hypertrophy for both functional and cosmetic reasons.

    • Mandibular fracture stabilization:

      • The masseter muscle exerts significant force on the mandible and can displace fractures, influencing surgical planning.

    • Trigger points and myofascial pain:

      • Chronic tension or overuse may lead to localized muscle knots, pain on palpation, and referral pain patterns.

    Did you know? Your thumb has two phalanges, whereas other fingers have three.