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    Related Topics

    From Musculoskeletal System

    Zygomaticus
    Muscle that raises the corners of the mouth.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Gliding (Plane) Joints
    e.g., between carpals
    Patella
    Knee cap, protecting the knee joint.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Carpals (8 bones)
    8 wrist bones.
    Clavicle
    Collarbone connecting the arm to the body.
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Sternum
    Breastbone located in the center of the chest.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Masseter
    Muscle that elevates the mandible.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.

    Trapezius

    Reviewed by our medical team

    Muscle responsible for moving, rotating, and stabilizing the scapula.

    1. Overview

    The trapezius is a large, superficial, triangular-shaped muscle that spans the upper back and neck. It is one of the most important muscles involved in the movement and stabilization of the scapula and upper limb. The trapezius also contributes to head and neck posture and plays a critical role in shoulder elevation and rotation.

    2. Location

    The trapezius occupies the posterior aspect of the neck and upper thorax:

    • Superiorly: Originates from the external occipital protuberance and nuchal ligament of the skull.

    • Medially: Arises from the spinous processes of C7 to T12 vertebrae.

    • Laterally: Inserts onto the lateral third of the clavicle, acromion, and spine of the scapula.

    • Superficial to: The rhomboids, levator scapulae, and deeper cervical and thoracic muscles.

    3. Structure

    The trapezius is divided into three functional parts:

    • Upper fibers: Run downward and laterally; elevate the scapula and extend the neck.

    • Middle fibers: Run horizontally; retract (adduct) the scapula.

    • Lower fibers: Run upward and laterally; depress and assist in upward rotation of the scapula.

    Other anatomical details:

    • Muscle type: Superficial skeletal muscle.

    • Innervation: Spinal accessory nerve (cranial nerve XI) for motor control; cervical spinal nerves (C3–C4) for proprioception.

    • Blood supply: Transverse cervical artery and dorsal scapular artery.

    4. Function

    The trapezius has several major actions depending on the portion activated:

    • Upper fibers: Elevate and upwardly rotate the scapula; extend and laterally flex the neck.

    • Middle fibers: Retract the scapula (pull toward the spine).

    • Lower fibers: Depress the scapula and contribute to upward rotation during arm elevation.

    Collectively, these actions contribute to proper positioning and motion of the shoulder girdle during arm movement.

    5. Physiological role(s)

    The trapezius serves multiple physiological and biomechanical functions:

    • Scapular stability: Maintains proper alignment of the scapula on the thoracic wall, crucial for upper limb mobility and strength.

    • Postural support: Keeps the shoulders aligned and the head upright during static postures and dynamic movements.

    • Upper limb coordination: Works synergistically with deltoid, serratus anterior, and rotator cuff muscles for smooth shoulder mechanics.

    • Proprioception: Provides feedback on position and movement of the shoulder and neck, aiding in coordination and balance.

    6. Clinical Significance

    The trapezius is frequently involved in musculoskeletal, neurological, and postural conditions:

    • Trapezius strain or overuse:

      • Common in individuals with poor posture, heavy lifting occupations, or prolonged computer use; presents as neck/shoulder tightness or pain.

    • Accessory nerve injury:

      • Damage to CN XI can lead to trapezius weakness or paralysis, resulting in shoulder drooping and difficulty elevating the arm.

      • Often occurs during neck surgery, lymph node biopsies, or trauma.

    • Myofascial pain syndrome:

      • Trigger points in the trapezius may refer pain to the neck, shoulders, or head; common cause of tension headaches.

    • Postural dysfunction:

      • Imbalance between upper and lower trapezius can contribute to conditions like rounded shoulders or forward head posture.

    • Rehabilitation relevance:

      • Trapezius strengthening and stretching are integral parts of physical therapy for shoulder and neck injuries.

    Did you know? Sesamoid bones are bones that form within tendons, like the patella.