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    From Musculoskeletal System

    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Diaphragm
    Primary muscle for breathing.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Wormian Bones
    Sutural bones in the skull.
    Adductors
    Muscles that bring the thighs toward the midline.
    Flexor Tendons
    Tendons that help flex the fingers and toes.
    Ilium
    Uppermost and largest part of the hip bone.
    Vomer Bone
    Bone forming the nasal septum.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Hinge Joints
    e.g., elbow, knee
    Radius
    Forearm bone on the thumb side.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    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.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Carpals (8 bones)
    8 wrist bones.
    Zygomaticus
    Muscle that raises the corners of the mouth.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Pivot Joints
    e.g., atlanto-axial joint
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.

    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? Bones become stronger when stressed by exercise.