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The scapula (pl.: scapulae or scapulas [1]), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side of the body being roughly a mirror image of the other.
The anatomical neck divides the head of the humerus from the greater and lesser tubercles of the humerus. It gives attachment to the capsular ligament of the shoulder joint except at the upper inferior-medial aspects.
It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). The body is cylindrical in its upper portion, and more prismatic below.
While this slightly closes the angle between the clavicle and the scapula, it also widens the shoulder. [4]: 40 The scapula can be elevated and depressed from the neutral position to a total range of 10 to 12 centimetres (3.9 to 4.7 in); at its most elevated position the scapula is always tilted so that the glenoid cavity is facing superiorly.
The coracoid process acts as an attachment and origin for a large number of muscles (attached muscles not labeled here). The coracoid process is a thick curved process attached by a broad base to the upper part of the neck of the scapula; [2] it runs at first upward and medially; then, becoming smaller, it changes its direction, and projects forward and laterally.
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 ...
In this highly specialized endoskeletal structure, the scapula is a dorsal (directed upwards) process attached to the first rib; the coracoid is a posteroventral (directed backward and down) process; and the acromion is a medioventral (directed inwards and down) process (also known as the prescapular process) located at the base of the scapula.
This ligament spans the neck and tail, and in modern birds maintains the concavity of the neck. [46] [69] Release of this ligament during decay was proposed to result in the characteristic death poses where the spine is strongly curved. [46] Diagram of the forelimb of Allosaurus showing the principal segments of the limb limb