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Questions and Answers
How many joints make up the shoulder complex, and which bones are involved?
How many joints make up the shoulder complex, and which bones are involved?
The shoulder complex is made up of 4 joints: glenohumeral, acromioclavicular, sternoclavicular, and scapulo-thoracic (not a real one). It includes 4 bones: sternum, clavicle, scapula, and humerus.
What is the name of the joint between the sternum and clavicle?
What is the name of the joint between the sternum and clavicle?
During elevation of the clavicle in the sternoclavicular joint, the clavicle is ____ and slides in the ____ direction.
During elevation of the clavicle in the sternoclavicular joint, the clavicle is ____ and slides in the ____ direction.
Which of the following movements occur at the sternoclavicular joint?
Which of the following movements occur at the sternoclavicular joint?
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The acromioclavicular joint is designed for maximum mobility.
The acromioclavicular joint is designed for maximum mobility.
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Which of the following movements occur at the acromioclavicular joint?
Which of the following movements occur at the acromioclavicular joint?
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During protraction, the acromioclavicular joint will ____.
During protraction, the acromioclavicular joint will ____.
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The scapulothoracic joint is a true synovial joint.
The scapulothoracic joint is a true synovial joint.
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Which of the following movements occur at the scapulothoracic joint?
Which of the following movements occur at the scapulothoracic joint?
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During ST elevation, the SC joint ____ and the AC joint ____.
During ST elevation, the SC joint ____ and the AC joint ____.
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During ST protraction, the SC joint ____ and the AC joint ____.
During ST protraction, the SC joint ____ and the AC joint ____.
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During abduction, the ____ joint upwardly rotates, the ____ joint elevates, and the ____ joint upwardly rotates.
During abduction, the ____ joint upwardly rotates, the ____ joint elevates, and the ____ joint upwardly rotates.
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What are the three degrees of freedom of the glenohumeral joint?
What are the three degrees of freedom of the glenohumeral joint?
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Describe the rolling and sliding motion of the humerus during external rotation at the glenohumeral joint.
Describe the rolling and sliding motion of the humerus during external rotation at the glenohumeral joint.
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Describe the rolling and sliding motion of the humerus during abduction at the glenohumeral joint.
Describe the rolling and sliding motion of the humerus during abduction at the glenohumeral joint.
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What is the scapulohumeral rhythm?
What is the scapulohumeral rhythm?
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Which of the following muscles are involved in scapulothoracic elevation?
Which of the following muscles are involved in scapulothoracic elevation?
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Which of the following muscles are involved in scapulothoracic depression?
Which of the following muscles are involved in scapulothoracic depression?
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Which of the following muscles are involved in scapulothoracic protraction?
Which of the following muscles are involved in scapulothoracic protraction?
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Which of the following muscles are involved in scapulothoracic upward rotation?
Which of the following muscles are involved in scapulothoracic upward rotation?
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Which muscles are involved in glenohumeral abduction?
Which muscles are involved in glenohumeral abduction?
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If the deltoid is paralyzed, which muscle can still abduct the arm? What happens if this muscle is also paralyzed?
If the deltoid is paralyzed, which muscle can still abduct the arm? What happens if this muscle is also paralyzed?
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Which of the following muscles are involved in glenohumeral flexion?
Which of the following muscles are involved in glenohumeral flexion?
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Which of the following muscles are involved in glenohumeral adduction and extension?
Which of the following muscles are involved in glenohumeral adduction and extension?
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Which of the following muscles are primarily involved in downward rotation of the scapula?
Which of the following muscles are primarily involved in downward rotation of the scapula?
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Which of the following muscles are involved in glenohumeral internal rotation?
Which of the following muscles are involved in glenohumeral internal rotation?
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During abduction, what happens at each joint of the shoulder complex?
During abduction, what happens at each joint of the shoulder complex?
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The brachial plexus is responsible for innervation of the lower extremities.
The brachial plexus is responsible for innervation of the lower extremities.
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Which of the following muscles are considered proximal stabilizers?
Which of the following muscles are considered proximal stabilizers?
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Which of the following muscles are considered distal mobilizers?
Which of the following muscles are considered distal mobilizers?
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Study Notes
Shoulder Complex Anatomy
- The shoulder complex is comprised of four joints: glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic.
- Four bones: humerus, scapula, clavicle, and sternum make up the shoulder complex.
Sternoclavicular (SC) Joint
- A synovial, bi-concave saddle joint between the sternum and clavicle.
- During elevation, the clavicle (convex) moves opposite to the sternum (concave).
- During protraction, the clavicle (concave) moves in the same direction as the sternum (convex).
- Movements include elevation/depression, protraction/retraction, and rotation of the clavicle (related to shoulder flexion).
Acromioclavicular (AC) Joint
- A gliding joint where the scapula and clavicle meet.
- More stable than the SC joint, allowing limited movement.
- Involved in movements like anterior/posterior tilt, protraction/retraction, abduction/adduction, scapular rotation, and upward/downward rotation.
- During protraction, the AC joint internally rotates.
- During elevation, the AC joint tilts anteriorly and downwardly rotates.
- During abduction, the AC joint upwardly rotates.
Scapulothoracic (ST) Joint
- Not a true joint, but an articulation plane between the scapula and the thorax.
- Involved in sliding movements.
- The scapula rests on the thorax with a slight anterior tilt (10 degrees) and internal rotation (35 degrees).
- Movements include elevation, depression, retraction, protraction, upward rotation, and downward rotation.
- During elevation, the SC joint elevates, and the AC joint downwardly rotates/anteriorly tilts.
- During protraction, the SC joint protracts, and the AC joint internally rotates.
- During abduction, the ST joint upwardly rotates, the SC joint elevates, and the AC joint upwardly rotates. (All "upward" movements).
Glenohumeral (GH) Joint
- A synovial ball-and-socket joint between the humeral head and glenoid fossa.
- Relatively low congruency resulting in high mobility and a potential for dislocation.
- Reinforcing and deepening tissues include the fibrous capsule, capsular ligaments, rotator cuff muscles (SITS), long head of biceps, and glenoid labrum.
GH Joint Motions and Stabilizers
- Motions: Flexion/extension, abduction/adduction, internal/external rotation, horizontal adduction/abduction.
- Flexion/Extension: Rotation in sagittal plane; flexion up to 120 degrees, complete ROM requires scapular upward rotation.
- Internal/External Rotation: During ER, the humerus rolls posteriorly and slides anteriorly; for IR, it rolls anteriorly and slides posteriorly.
- Abduction: Superior roll and inferior glide of humerus on glenoid fossa.
- 2:1 Scapulohumeral Rhythm: 120° of GH abduction combined with 60° of ST upward rotation is needed to reach 180° of abduction.
Stabilizing Mechanisms
- Static Locking Mechanism: Superior capsular structures (supraspinatus tendon, superior capsular ligament, coracohumeral ligament) maintain the humeral head in the glenoid cavity, preventing subluxation (partial dislocation).
- Dynamic Locking Mechanisms: Supporting muscles (rotator cuff, biceps) play a part in stabilizing and centering the humeral head within the glenoid.
Innervation and Muscles
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Brachial Plexus: Responsible for innervation of the upper extremities.
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Proximal Stabilizers: Originate from spine, ribs, or cranium to attach to the scapula and clavicle.
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Distal Mobilizers: Originate on the scapula and/or clavicle to attach to the humerus or forearm.
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Specific muscles are listed for each movement. (There are too many to individually list here, but the mnemonics are included).
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Description
Test your knowledge on the anatomy of the shoulder complex, including its joints and bones. This quiz covers important movements and characteristics of the shoulder's key joints such as the sternoclavicular and acromioclavicular joints. Perfect for anatomy students and enthusiasts!
