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    Related Topics

    From Musculoskeletal System

    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Cranial Bones
    Bones of the skull that protect the brain.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Hinge Joints
    e.g., elbow, knee
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Clavicle
    Collarbone connecting the arm to the body.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Sacrum
    Triangular bone at the base of the spine.
    Flexor Tendons
    Tendons that help flex the fingers and toes.
    Phalanges (14 bones)
    14 bones forming the toes.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Facial Bones
    Bones forming the structure of the face.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Sternum
    Breastbone located in the center of the chest.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.

    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? The metatarsals are the bones in the feet that connect to the toes.