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Multiple Choice
Which powerful muscle is the prime mover of arm extension?
A
Biceps brachii
B
Pectoralis major
C
Deltoid
D
Latissimus dorsi
Verified step by step guidance
1
Step 1: Understand the concept of a 'prime mover' in muscle anatomy. A prime mover, or agonist, is the muscle primarily responsible for producing a specific movement during contraction.
Step 2: Review the function of the latissimus dorsi muscle. The latissimus dorsi is a large, flat muscle located in the lower back that plays a key role in arm extension, adduction, and medial rotation.
Step 3: Compare the functions of the other muscles listed in the problem:
- Biceps brachii: Primarily involved in flexion of the elbow and supination of the forearm.
- Pectoralis major: Responsible for flexion, adduction, and medial rotation of the arm.
- Deltoid: Primarily involved in abduction of the arm.
Step 4: Identify that arm extension refers to moving the arm backward, which is a movement primarily performed by the latissimus dorsi muscle.
Step 5: Conclude that the latissimus dorsi is the prime mover of arm extension based on its anatomical location and function.