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    Related Topics

    From Musculoskeletal System

    Deltoid
    Shoulder muscle responsible for arm abduction.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Sacrum
    Triangular bone at the base of the spine.
    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.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Radius
    Forearm bone on the thumb side.
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Glenohumeral Ligaments
    Shoulder ligaments that stabilize the shoulder joint.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Tarsals (7 bones)
    7 ankle bones.
    Hinge Joints
    e.g., elbow, knee
    Interspinous Ligament
    Spinal ligament between adjacent vertebral spinous processes.
    Anterior Cruciate Ligament (ACL)
    Knee ligament that stabilizes the joint.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Diaphragm
    Primary muscle for breathing.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Carpals (8 bones)
    8 wrist bones.

    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? Ligaments hold bones together and are tough yet flexible.