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

10. Muscles

Muscle Naming

Anatomy & Physiology

10. Muscles

Muscle Naming

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Problem 9

Textbook Question

Which of the erector spinae muscles is most lateral to the vertebral column?
a. Spinalis muscle
b. Iliocostalis muscle
c. Semispinalis muscle
d. Longissimus muscle

Verified step by step guidance

Understand the anatomy of the erector spinae muscle group, which consists of three primary muscles: spinalis, longissimus, and iliocostalis. These muscles run parallel to the vertebral column and are responsible for extending and stabilizing the spine.

Identify the relative positions of the muscles within the erector spinae group. The spinalis muscle is the most medial, located closest to the vertebral column. The longissimus muscle is intermediate, positioned between the spinalis and iliocostalis muscles.

Recognize that the iliocostalis muscle is the most lateral of the erector spinae group. It is positioned furthest from the vertebral column and attaches to the ribs and iliac crest, contributing to lateral flexion and extension of the spine.

Exclude the semispinalis muscle from consideration, as it is not part of the erector spinae group. The semispinalis muscle belongs to the transversospinalis group and is located deeper in the back, closer to the vertebral column.

Conclude that the iliocostalis muscle is the correct answer because it is the most lateral muscle within the erector spinae group, based on its anatomical position and function.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Erector Spinae Muscles

The erector spinae is a group of muscles that run along the spine and are responsible for extending and laterally flexing the vertebral column. This group consists of three primary muscles: iliocostalis, longissimus, and spinalis. Understanding their locations and functions is crucial for identifying which muscle is most lateral.

Muscle Anatomy and Positioning

In anatomy, the positioning of muscles relative to each other is essential for understanding their functions and interactions. The terms 'lateral' and 'medial' describe the position of structures in relation to the midline of the body. In the context of the erector spinae, knowing which muscle lies furthest from the vertebral column helps in answering questions about their anatomical arrangement.

Spinal Muscle Functions

The erector spinae muscles play a vital role in maintaining posture and enabling movements of the spine, such as extension and rotation. Each muscle within this group has specific functions and contributes differently to spinal stability and mobility. Recognizing these functions aids in understanding why certain muscles are positioned as they are in relation to the vertebral column.