Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

9. Muscle Tissue

Introduction to Muscles and Muscle Tissue

Anatomy & Physiology

9. Muscle Tissue

Introduction to Muscles and Muscle Tissue

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Multiple Choice

Which muscle is the prime mover of arm abduction when all its fibers are used?

Biceps brachii

Pectoralis major

Latissimus dorsi

Deltoid

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Verified step by step guidance

Step 1: Understand the concept of a 'prime mover' in muscle actions. A prime mover, also known as an agonist, is the muscle primarily responsible for generating a specific movement.

Step 2: Review the anatomy and function of the deltoid muscle. The deltoid is a triangular-shaped muscle located on the shoulder. It has three distinct sets of fibers: anterior, middle, and posterior. When all fibers contract together, the deltoid is responsible for arm abduction, which is the movement of the arm away from the midline of the body.

Step 3: Compare the deltoid's function to the other muscles listed in the problem. The biceps brachii is primarily involved in elbow flexion and forearm supination, not arm abduction. The pectoralis major is responsible for arm flexion, adduction, and medial rotation, while the latissimus dorsi is involved in arm extension, adduction, and medial rotation.

Step 4: Recognize that arm abduction requires a muscle that can lift the arm away from the body laterally. The deltoid, specifically its middle fibers, is uniquely suited for this action when all fibers are engaged.

Step 5: Conclude that the deltoid is the prime mover for arm abduction when all its fibers are used, as it is anatomically and functionally designed for this movement.