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The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints .
The rotator cuff muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid cavity. The glenoid cavity is shallow and contains the glenoid labrum which deepens it and aids stability. With 120 degrees of unassisted flexion, the shoulder joint is the most mobile joint in the body.
In primates, the arm is adapted for precise positioning of the hand and thus assist in the hand's manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the structure of the two forearm bones which can rotate around each other allows for additional range of motion at that level. [16]
It joins with the scapula above at the shoulder joint (or glenohumeral joint) and with the ulna and radius below at the elbow joint. Notice : When the arm is spun so that the thumb point to the outside of the body, meaning the palm of the hand looks forward then it is said the hand is supinated.
The shoulder girdle [5] or pectoral girdle, [6] composed of the clavicle and the scapula, connects the upper limb to the axial skeleton through the sternoclavicular joint (the only joint in the upper limb that directly articulates with the trunk), a ball and socket joint supported by the subclavius muscle which acts as a dynamic ligament. While ...
The bone or other structure the muscle is attached to that remains immobile during the action. The term "bone" is omitted from bone names. Insertion The attachment point of the muscle, on a bone or otherwise, that moves during the action. Artery The artery which supplies the muscle with blood. The term "artery" is included to avoid confusing ...
The humerus (/ ˈ h juː m ər ə s /; pl.: humeri) is a long bone in the arm that runs from the shoulder to the elbow.It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections.
The glenohumeral joint has been analogously described as a golf ball (head of the humerus) sitting on a golf tee (glenoid fossa). [5] The rotator cuff compresses the glenohumeral joint during abduction of the arm, an action known as concavity compression, in order to allow the large deltoid muscle to further elevate the arm. In other words ...