ANATOMY & PHYSIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site shoulder The area of the body where the arm attaches to the trunk. The rounded bony surface at the front of the shoulder is the upper part of the humerus (upper-arm bone); the bony surfaces that form the top and back of the shoulder are parts of the scapula (shoulderblade). The clavicle (collarbone) articulates with the acromion (the bony prominence at the outer top of the scapula) at the acromioclavicular joint and extends across the top of the chest to the sternum (breastbone), to which it is attached at the sternoclavicular joint. Just below the acromion, on the outer wall of the scapula, is a socket (called the glenoid cavity) into which the head of the humerus fits to form the shoulder joint. A bursa (fluid-filled sac) under the acromion reduces friction at the joint. The shoulder joint is a ball-and-socket joint with a wide range of movement produced by part of the biceps muscle, several smaller muscles that make up the rotator cuff, various muscles in the chest wall, and the deltoid muscle (the muscle at the top of the upper arm and shoulder). Related category    • ANATOMY AND PHYSIOLOGY Source: British Medical Association Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP