Overview of the Skeletal System

Introduction

The human skeletal system is a complex framework composed of approximately 206 bones and their associated cartilages. It provides structural support, protection for internal organs, and facilitates movement through its interaction with muscles.

Structure of the Skeletal System and Skeletal Cartilages

Main Divisions of the Skeleton

• Axial Skeleton

• Appendicular Skeleton

Each division has distinct roles in support, protection, and movement.

Axial Skeleton

Definition and Function

The axial skeleton forms the body's longitudinal axis and encases major body cavities, providing protection for underlying organs.

• Skull: Consists of 22 bones (8 cranial and 14 facial) that encase the brain and form the face.

• Vertebral Column: Composed of 33 bones. 24 are individual vertebrae that protect the spinal cord; the remaining vertebrae are fused to form the sacrum and coccyx.

• Thoracic Cage (Rib Cage): Includes 12 pairs of ribs, the sternum, and part of the vertebral column. It encases and protects the lungs, heart, and other delicate contents of the thoracic cavity.

Example: The rib cage protects the heart and lungs from physical trauma.

Appendicular Skeleton

Definition and Function

The appendicular skeleton consists of the bones of the pectoral girdle, upper limb, pelvic girdle, and lower limb. Its structure is primarily suited for movement, support, and muscle attachment.

• Pectoral Girdle: Composed of the clavicle and scapula; anchors the upper limb to the trunk.

• Upper Limb: Divided into three parts:

  • Arm: Humerus

  • Forearm: Radius and ulna

  • Wrist and Hand: Carpals, metacarpals, and phalanges

• Pelvic Girdle: Supports the lower limb and anchors it to the trunk.

• Lower Limb: Includes the femur (thigh), tibia and fibula (leg), and the bones of the ankle and foot (tarsals, metatarsals, and phalanges).

Example: The pectoral girdle allows for a wide range of motion in the upper limb, essential for tasks such as lifting and throwing.

Key Terms

• Cartilage: A flexible connective tissue found in various forms in the larynx and respiratory tract, in structures such as the external ear and the articulating surfaces of joints.

• Epiphysis: The end part of a long bone, initially growing separately from the shaft.

• Diaphysis: The shaft or central part of a long bone.

Summary Table: Axial vs. Appendicular Skeleton

Additional info: The axial skeleton is essential for protecting the central nervous system and vital organs, while the appendicular skeleton is crucial for mobility and manipulation of the environment.