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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.
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.
The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder.The word glenoid is pronounced / ˈ ɡ l iː n ɔɪ d / or / ˈ ɡ l ɛ n ɔɪ d / (both are common) and is from Greek: gléne, "socket", reflecting the shoulder joint's ball-and-socket form. [1]
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 shoulder joint is a ball-and-socket joint between the scapula and the humerus. The socket of the glenoid fossa of the scapula is itself quite shallow, but it is made deeper by the addition of the glenoid labrum. The glenoid labrum is a ring of cartilaginous fibre attached to the circumference of the cavity.
"In terms of comparative anatomy the human scapula represents two bones that have become fused together; the (dorsal) scapula proper and the (ventral) coracoid. The epiphyseal line across the glenoid cavity is the line of fusion. They are the counterparts of the ilium and ischium of the pelvic girdle." —
The deltoid originates on the lateral third of the clavicle, acromion and the crest of the spine of the scapula. It is inserted on the deltoid tuberosity of the humerus and has several actions including abduction, extension, and circumduction of the shoulder. The supraspinatus also originates on the spine of the scapula. It inserts on the ...
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.