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Questions and Answers
Which bones are included in the shoulder complex?
What type of joint is the scapulothoracic joint classified as?
Which of the following joints are involved in the arthrokinematic motions of the shoulder complex?
What does the sternoclavicular joint connect?
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What movement occurs in the opposite direction when the arm is elevated?
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Which joint is primarily responsible for optimizing movement rather than providing extensive range of motion?
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What is the primary motion of the scapulothoracic joint?
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When retracting the shoulder girdle, what occurs at the acromioclavicular joint?
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What type of joint is the acromioclavicular (AC) joint classified as?
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What is the primary motion occurring at the acromioclavicular (AC) joint during shoulder elevation?
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How does scapulohumeral rhythm describe the relationship between shoulder abduction and joint motion?
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What is the primary disadvantage of the large range of motion at the glenohumeral joint?
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How does the motion of the scapula occur during shoulder shrugging?
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Study Notes
Shoulder Complex Osteology
- The shoulder complex is comprised of five bones: humerus, clavicle, scapula, sternum, and ribs.
- Four joints form the shoulder complex: glenohumeral, acromioclavicular (AC), sternoclavicular (SC), and scapulothoracic.
- The scapulothoracic joint is not a true joint, but rather a point of contact between the scapula and ribs.
- The sternoclavicular joint is a saddle joint, which allows for greater stability at the junction between the appendicular and axial skeletons.
Shoulder Complex Arthrokinematics
- The clavicle has three degrees of freedom: elevation/depression, protraction/retraction, and rotation.
- The AC joint optimizes movement and allows for upward and downward rotation.
- The scapulothoracic joint movements are facilitated by the SC and AC joints and include: elevation/depression, adduction/abduction (protraction/retraction), and upward/downward rotation.
- Scapulohumeral rhythm describes the coordinated motion between the glenohumeral and scapulothoracic joints for full shoulder movement.
Glenohumeral Joint
- The glenohumeral joint is a ball-and-socket joint, where the humeral head is convex and the glenoid fossa is concave.
- The glenohumeral joint has a significant size mismatch between the humeral head and glenoid fossa, contributing to its large range of motion but also its instability.
- During abduction, the humeral head rolls superiorly and slides inferiorly. This motion requires a strong inferior capsular ligament to prevent impingement syndrome.
- During flexion and extension, the humeral head primarily spins within the glenoid fossa.
- During external rotation, the humeral head rolls posteriorly and slides anteriorly, while the infraspinatus muscle contracts.
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Description
Explore the intricate details of the shoulder complex's osteology and arthrokinematics. This quiz covers the bones, joints, and motions involved in shoulder movement. Understand the relationships and functions of these components for comprehensive knowledge of the shoulder complex.
