Podcast
Questions and Answers
The medial pull of the supraspinatus helps to prevent inferior displacement of the humeral head.
The medial pull of the supraspinatus helps to prevent inferior displacement of the humeral head.
True
The infraspinatus muscle is primarily responsible for shoulder flexion.
The infraspinatus muscle is primarily responsible for shoulder flexion.
False
Weakness in the rotator cuff can lead to increased superior glide of the humeral head during shoulder elevation.
Weakness in the rotator cuff can lead to increased superior glide of the humeral head during shoulder elevation.
True
The deltoid muscle does not contribute to the abduction of the shoulder joint.
The deltoid muscle does not contribute to the abduction of the shoulder joint.
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All elements including the deltoid, supraspinatus, and depressors are necessary for shoulder elevation.
All elements including the deltoid, supraspinatus, and depressors are necessary for shoulder elevation.
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The trapezius muscle only acts at the sternoclavicular joint.
The trapezius muscle only acts at the sternoclavicular joint.
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The middle trapezius is primarily responsible for scapular abduction.
The middle trapezius is primarily responsible for scapular abduction.
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Isolated weakness of the middle trapezius is a common condition.
Isolated weakness of the middle trapezius is a common condition.
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The lower trapezius is ideal for the elevation of the scapula.
The lower trapezius is ideal for the elevation of the scapula.
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The combined action of the upper and lower trapezius allows the scapula to rotate downwards.
The combined action of the upper and lower trapezius allows the scapula to rotate downwards.
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The trapezius muscle plays a larger role in shoulder flexion than in shoulder abduction.
The trapezius muscle plays a larger role in shoulder flexion than in shoulder abduction.
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Serratus anterior muscle is primarily responsible for scapular protraction.
Serratus anterior muscle is primarily responsible for scapular protraction.
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The trapezius muscle lies primarily in the sagittal plane.
The trapezius muscle lies primarily in the sagittal plane.
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The serratus anterior muscle primarily causes scapular adduction.
The serratus anterior muscle primarily causes scapular adduction.
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Weakness in the levator scapulae can lead to a posture characterized by rounded shoulders.
Weakness in the levator scapulae can lead to a posture characterized by rounded shoulders.
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The pectoralis minor muscle is located entirely on the posterior surface of the thorax.
The pectoralis minor muscle is located entirely on the posterior surface of the thorax.
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The primary action of the rhomboid muscles is scapular elevation.
The primary action of the rhomboid muscles is scapular elevation.
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Scapular downward rotation can occur when reaching into a back hip pocket.
Scapular downward rotation can occur when reaching into a back hip pocket.
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The pectoralis minor contributes to scapular abduction by pulling on the coracoid process.
The pectoralis minor contributes to scapular abduction by pulling on the coracoid process.
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The levator scapulae produces contralateral rotation of the cervical spine.
The levator scapulae produces contralateral rotation of the cervical spine.
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Scapular elevation occurs when the pectoralis minor contracts alone.
Scapular elevation occurs when the pectoralis minor contracts alone.
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The pectoralis minor contributes to the downward rotation of the scapula by abducting it.
The pectoralis minor contributes to the downward rotation of the scapula by abducting it.
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The subclavius muscle primarily assists in the elevation of the sternoclavicular joint.
The subclavius muscle primarily assists in the elevation of the sternoclavicular joint.
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The serratus anterior provides balance to the adduction component of the trapezius during arm elevation.
The serratus anterior provides balance to the adduction component of the trapezius during arm elevation.
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The scapulohumeral muscles do not contribute to dynamic stabilization of the glenohumeral joint.
The scapulohumeral muscles do not contribute to dynamic stabilization of the glenohumeral joint.
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The deltoid muscle is involved in shoulder horizontal abduction.
The deltoid muscle is involved in shoulder horizontal abduction.
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The supraspinatus muscle helps stabilize the glenohumeral joint by applying a vertical force to hold the humeral head.
The supraspinatus muscle helps stabilize the glenohumeral joint by applying a vertical force to hold the humeral head.
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The rhomboids exclusively perform shoulder flexion.
The rhomboids exclusively perform shoulder flexion.
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Shoulder flexion is one of the actions performed by the anterior deltoid.
Shoulder flexion is one of the actions performed by the anterior deltoid.
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Study Notes
Kinetics of Shoulder
- The shoulder's kinetics involves the movement and forces acting on the shoulder joint.
- The presented slides cover the various muscles that act on the shoulder, specifically the trapezius, serratus anterior, pectoralis minor, and subclavius.
- The trapezius plays a role in scapular elevation, adduction, and upward rotation.
- The middle trapezius is a pure scapular adductor, with horizontally aligned fibers contributing to its strength in scapular adduction and stabilization.
- Isolated weakness of the middle trapezius is uncommon, potentially arising from prolonged stretching, often associated with scapular abduction.
- The lower trapezius is vital for scapular depression and adduction, with its line of pull optimal for scapular depression.
- During prone positions, the weight of the upper extremities reduces the need for lower trapezius activity compared to upright postures.
- The combined action of the upper and lower trapezius muscles enables scapular upward rotation without displacement.
- The trapezius, as a whole, contributes to scapular upward rotation, which is crucial for arm movement and trunk flexion.
- The trapezius plays a more significant role in shoulder abduction than flexion.
- The serratus anterior facilitates scapular abduction, upward rotation, and elevation, often described as scapular protraction in textbooks.
- The trapezius and serratus anterior interact to produce scapular movement, with their respective pulling forces counteracting and coordinating for upward rotation and stability.
- The levator scapulae, rhomboid major, and minor muscles cause contralateral cervical spine rotation and ipsilateral scapular rotation; and contribute to scapular adduction and downward rotation.
- The muscles' actions may be utilized in daily activities such as reaching or scratching the back.
- Weakness of these muscles can lead to issues with pulling actions and contribute to posture problems like rounded shoulders.
- The pectoralis minor is an unusual muscle, entirely on the thorax's anterior surface, attaching to the coracoid process of the scapula.
- The pectoralis minor contributes to scapular anterior tilt, elevation, depression, adduction, and abduction with other muscles.
- The pectoralis minor's anterior pull on the coracoid process causes scapular abduction.
- The pectoralis minor and the rhomboids work together in a force couple to promote downward rotation of the scapula.
- The subclavius muscle, connecting the clavicle to the first rib, acts principally as a stabilizer of the sternoclavicular joint, countering forces that would elevate it, such as weight bearing.
- During arm elevation, the whole trapezius requires support from the serratus anterior to balance its adduction component.
- The scapulohumeral muscles facilitate movement and dynamic stabilization of the glenohumeral joint, contributing substantially to the shoulder's range of motion.
- The scapulohumeral group includes the deltoid, teres major, coracobrachialis, and the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis).
- The anterior deltoid is associated with shoulder flexion, medial rotation and abduction.
- The posterior deltoid is related to shoulder extension, lateral rotation, and abduction.
- The supraspinatus is crucial for stabilizing the glenohumeral joint by pulling on the humeral head, preventing inferior dislocation and supporting movement.
- The infraspinatus is a key lateral rotator and contributes to shoulder horizontal abduction and stability.
- The rotator cuff muscles are essential for stabilizing the glenohumeral joint during arm movements, preventing visible instability and dislocations, even with significant disruptions.
- The deltoid, supraspinatus, and scapular depressors (including infraspinatus, teres minor, and subscapularis) are vital for shoulder abduction and elevation.
- The action of these muscles, maintaining joint compression, and humeral head stabilization, ensures proper shoulder movement and function.
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Description
Test your knowledge on the anatomy and function of shoulder muscles, including the role of the trapezius, supraspinatus, and infraspinatus. This quiz covers key concepts related to shoulder elevation, abduction, and the contributions of various muscles. Assess your understanding of shoulder biomechanics and common conditions associated with muscle weakness.
