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Multiple Choice
Which muscle acts as the prime mover of shoulder flexion and adduction?
A
Latissimus dorsi
B
Pectoralis major
C
Deltoid
D
Trapezius
Verified step by step guidance
1
Step 1: Understand the terms 'prime mover,' 'shoulder flexion,' and 'adduction.' The prime mover is the muscle primarily responsible for a specific movement. Shoulder flexion refers to moving the arm forward and upward, while adduction refers to bringing the arm closer to the body's midline.
Step 2: Review the anatomical functions of the muscles listed in the options: Latissimus dorsi, Pectoralis major, Deltoid, and Trapezius. Identify which muscle is primarily responsible for both shoulder flexion and adduction.
Step 3: Analyze the Pectoralis major. This muscle is located in the chest and is responsible for movements such as shoulder flexion, adduction, and internal rotation. It acts as the prime mover for these actions.
Step 4: Compare the Pectoralis major to the other muscles listed. The Latissimus dorsi primarily performs shoulder extension and adduction but not flexion. The Deltoid is involved in shoulder abduction and flexion but is not the prime mover for adduction. The Trapezius is responsible for scapular movements, not shoulder flexion or adduction.
Step 5: Conclude that the Pectoralis major is the correct answer because it is the prime mover for both shoulder flexion and adduction, based on its anatomical function and location.