Muscles of the Back

  1. Trapezius: This muscle is large and covers the upper back and neck. It's involved in several movements:

    • Elevate the shoulders.
    • Retract (squeeze together) the scapulae.
    • Depress the shoulders and assist in upward rotation of the scapulae.

  2. Latissimus Dorsi: Located on the sides of the back, it assists in:
    • Extension: Pulling the arm down and back toward the body.
    • Adduction: Bringing the arm closer to the midline of the body.

  3. Rhomboids (Major and Minor): Found between the spine and the scapulae, these muscles retract the scapulae, pulling them towards the spine.

Muscles of the Shoulder:

  1. Deltoid: This large muscle forms the rounded contour of the shoulder and has three sets of fibers:

    • Flex the shoulder (bringing the arm forward).
    • Abduct (raise) the arm to the side.
    • Extend the shoulder (moving the arm backward).

  2. Rotator Cuff Muscles (Supraspinatus, Infraspinatus, Teres Minor, Teres Major, Subscapularis): These muscles are crucial for stabilizing the shoulder joint and rotating the arm. They assist in various movements, including abduction, external and internal rotation, and stabilization of the shoulder during arm movements.

  3. Pectoralis Major: Located in the chest area, it contributes to movements like:
    • Adduction: Bringing the arm across the body.
    • Medial rotation: Rotating the arm inwardly.

muscles