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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 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.
The scapula is moved posteriorly and medially along the back, moving the arm and shoulder joint posteriorly. Retracting both scapulae gives a sensation of "squeezing the shoulder blades together." rhomboideus major, minor, and trapezius Scapular protraction [10] (aka scapular abduction) The opposite motion of scapular retraction.
From its neutral position, the shoulder girdle can be rotated about an imaginary vertical axis at the medial end of the clavicle (the sternoclavicular joint). Throughout this movement the scapula is rotated around the chest wall so that it moves 15 centimetres (5.9 in) laterally and the glenoid cavity is rotated 40–45° in the horizontal plane.
The shoulder joint involves articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the upper arm bone and functions as a diarthrosis and multiaxial joint. Due to the very loose joint capsule that gives a limited interface of the humerus and scapula, it is the most mobile joint of the human body.
In human anatomy, the acromion (from Greek: akros, "highest", ōmos, "shoulder", pl.: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process, it extends laterally over the shoulder joint. The acromion is a continuation of the scapular spine, and hooks over anteriorly.
The most important ligament involved in shoulder joint stability is the Inferior Glenohumeral Ligament. During abduction of the arm, the middle and inferior ligaments become taut while the superior ligament relaxes. The radius of curvature of the head of the humerus is greater superiorly than inferiorly, which further stretches these ligaments ...
The supraspinous fossa is bounded by the spine of scapula on the inferior side, acromion process on the lateral side and the superior angle of scapula on the superior side. Supraspinatus muscle originates from the supraspinous fossa. Distal attachment of the levator scapulae muscle is also on the medial aspect of the fossa.