The shoulder is arranged into 3  layers:-

Bones and joints     5 4       Ligaments  5 5    Muscles & Tendons

    

 The shoulder has the greatest range of movement of all joints in human anatomy. It is a ball and socket joint; the ball is the head of the humerus and the socket is the glenoid (part of the scapula or shoulder blade).

     

Three bones make up the shoulder; these are the clavicle, humerus and scapula. The joint between the clavicle and scapula is called the acromio-clavicular joint. The clavicle acts as a strut between the breast bone  and the shoulder. The joint between the humerus and scapula is called the gleno-humeral joint. The head of the humerus has 2 projections, the greater and lesser tuberosities. It is at these points that the rotator cuff tendons attach. The scapula is a complex bone. The glenoid fossa is a shallow cavity which articulates with the humerus. The edge of the glenoid fossa is surrounded by a cartilage structure called the 5 4 glenoid labrum. The labrum acts like a curved bumper to increase the depth of the glenoid fossa. It thus keeps the humeral head in the glenoid fossa and helps to prevent dislocations. The 5 4 biceps tendon and several ligaments attach to the labrum and also help to prevent dislocations.