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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. But when the thumb remains in the inside and the ...
Shoulder anatomy, front view Shoulder anatomy, back view. The rotator cuff is an anatomical term given to the group of four muscles and their tendons that act to stabilize the shoulder. [3] These muscles are the supraspinatus, infraspinatus, teres minor and subscapularis and that hold the head of the humerus in the glenoid cavity during ...
The light bulb sign is best observed on an AP radiograph of the shoulder. [5] Key features include: Rounded humeral head: The humeral head appears symmetrically rounded, resembling a light bulb due to internal rotation. Loss of normal glenohumeral overlap: The humeral head is posteriorly displaced, disrupting the alignment with the glenoid cavity.
Muscles are often paired as agonistic and antagonistic muscles. [20] This can be a bit misleading as, in general, it is groups of muscles working together to either make or cancel a movement. [21] The present table lists some well-known relationships but is not at all complete.
Anterior and posterior views of the proximal humerus with labeled bony landmarks and muscle insertion sites. The shoulder joint consists of the glenoid cavity of the scapula and the head of the humerus. It as an extremely mobile joint that is stabilized by surrounding soft tissues such as the joint capsule, muscles, and ligaments. [11]
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.
The shoulder joint is considered a ball-and-socket joint. However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus). The socket is deepened by the glenoid labrum, stabilizing the shoulder joint. [1] [2]
The mobility of the shoulder girdle is supported by a large number of muscles. The most important of these are muscular sheets rather than fusiform or strap-shaped muscles and they thus never act in isolation but with some fibres acting in coordination with fibres in other muscles. [6] Muscles of shoulder girdle excluding the glenohumeral joint [4]