Chapter 6: The Skeletal System – Essentials of Anatomy & Physiology

Overview of the Skeletal System

Introduction to the Skeletal System

The skeletal system is a fundamental organ system in the human body, providing structure, protection, and support. It consists of approximately 206 bones, as well as cartilages, ligaments, and connective tissues.

• Axial Skeleton: Includes bones of the skull, thorax, and vertebral column. Forms the longitudinal axis of the body.

• Appendicular Skeleton: Includes bones of the limbs and the pectoral and pelvic girdles.

Example: The axial skeleton contains 80 bones, while the appendicular skeleton contains 126 bones.

Divisions of the Skeleton

Axial Skeleton

The axial skeleton consists of the bones of the skull and associated bones, the thoracic cage, and the vertebral column. It serves several critical functions:

• Support and Protection: Protects the brain and spinal cord.

• Muscle Attachment: Provides surfaces for muscles that adjust the position of the head, neck, and trunk, perform respiratory movements, and stabilize parts of the appendicular skeleton.

Appendicular Skeleton

The appendicular skeleton includes the bones of the limbs and the supporting girdles (pectoral and pelvic) that connect the limbs to the trunk.

• Function: Facilitates movement and interaction with the environment.

Summary Table: Axial vs. Appendicular Skeleton

Division	Main Components	Number of Bones	Main Functions
Axial Skeleton	Skull, thoracic cage, vertebral column	80	Protection, support, muscle attachment
Appendicular Skeleton	Limbs, pectoral girdle, pelvic girdle	126	Movement, interaction with environment

Key Terms and Definitions

• Bone: Rigid organ that constitutes part of the vertebrate skeleton.

• Cartilage: Flexible connective tissue found in joints between bones.

• Ligament: Fibrous connective tissue that connects bones to other bones.

• Connective Tissue: Tissue that supports, binds, or separates other tissues or organs.

Applications and Importance

• Clinical Relevance: Understanding the divisions and functions of the skeletal system is essential for diagnosing and treating musculoskeletal disorders.

• Movement: The appendicular skeleton is crucial for locomotion and manipulation of objects.

• Protection: The axial skeleton protects vital organs such as the brain, heart, and lungs.

Additional info: The skeletal system also plays a role in mineral storage (e.g., calcium and phosphate) and blood cell production (hematopoiesis in bone marrow).