Shoulders

The shoulder is made up of several layers, including the following:

  • bones - the collarbone (clavicle), the shoulder blade (scapula), and the upper arm bone (humerus).
  • joints - facilitate movement, including the following:
    • clavicle
    • acromioclavicular (AC) joint (where the clavicle meets the acromion)
    • shoulder joint (glenohumeral joint) - a ball-and-socket joint that facilitates forward, circular, and backward movement of the shoulder.
  • ligaments - a white, shiny, flexible band of fibrous tissue that binds joints together and connects various bones and cartilage, including the following:
    • joint capsule - a group of ligaments that connect the humerus to the socket of the shoulder joint on the scapula to stabilize the shoulder and keep it from dislocating
    • ligaments that attach the clavicle to the acromion
    • ligaments that connect the clavicle to the scapula by attaching to the coracoid process
  • acromion - the roof (highest point) of the shoulder that is formed by a part of the scapula.
  • tendons - the tough cords of tissue that connect muscles to bones. The rotator cuff tendons are a group of tendons that connect the deepest layer of muscles to the humerus.
  • muscles (to help support and rotate the shoulder in many directions)
  • bursa - a closed space between two moving surfaces that has a small amount of lubricating fluid inside; located between the rotator cuff muscle layer and the outer layer of large, bulky muscles.
  • rotator cuff - composed of tendons, the rotator cuff (and associated muscles) holds the ball of the glenohumeral joint at the top of the upper arm bone (humerus). The shoulder joint is known as a ball-and-socket joint, allowing the backward, forward, sideways and rotating movements.