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    Related Topics

    From Musculoskeletal System

    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Zygomaticus
    Muscle that raises the corners of the mouth.
    Mandible
    Lower jawbone that houses the teeth.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Hinge Joints
    e.g., elbow, knee
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Biceps Tendon
    Tendon that attaches the biceps muscle to the bone.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Wormian Bones
    Sutural bones in the skull.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Patella
    Knee cap, protecting the knee joint.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Extensor Tendons
    Tendons that help extend the fingers and toes.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Diaphragm
    Primary muscle for breathing.

    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 feet contain 26 bones.