classification of bones

Overview of the Skeleton

  • Definition of the Skeleton: The skeleton is a network of bones that are connected at joints, serving as the structural foundation of the body.

  • Functions of the Skeleton:

    • Protects vital internal organs.

    • Provides framework for body shape.

    • Facilitates movement in conjunction with muscles.

Main Divisions of the Skeleton

  • The human skeleton consists of two primary divisions:

    1. Axial Skeleton:

    • Located on the midline of the body.

    • Components include:

      • Skull: Protects the brain.

      • Vertebral Column: Composed of vertebrae, protects the spinal cord.

      • Sternum: Center of the rib cage.

      • Laryngeal Skeleton: Supports the larynx.

      • Thoracic Cage: Comprised of ribs and vertebrae, protects the heart and lungs.

    1. Appendicular Skeleton:

    • Consists of bones in the shoulder (pectoral girdle) and pelvis (pelvic girdle) as well as the limbs.

    • Functions:

      • Pectoral Girdle and Upper Limbs:

        • Specialized for flexibility and increased range of motion (e.g., reaching, lifting).

      • Pelvic Girdle and Lower Limbs:

        • Specialized for strength and support of body weight (e.g., walking, running).

Visual Representation of Skeleton

  • Figure 3.6 illustrates:

    • Axial skeleton (in blue): includes the skull, thoracic cage, and vertebral column.

    • Appendicular skeleton (in white): contains bones of the shoulder and pelvic girdles, as well as the upper and lower limbs.

Bone Types

  • Classification Criteria: Bones are classified by their structure and shape, which ultimately determines their function.

  • Types of Bones:

    1. Long Bones:

    • Description: Long and thin.

    • Function: Support body weight and enable movement.

    • Examples: Humerus, ulna, radius, tibia, fibula, metacarpals, metatarsals.

    1. Flat Bones:

    • Description: Very thin with parallel surfaces.

    • Function: Protect underlying organs (e.g., brain).

    • Examples: Bones of the cranium, sternum, ribs, scapula.

    1. Sutural Bones:

    • Description: Small and flat.

    • Function: Found between the flat bones of the skull; number varies per individual.

    1. Short Bones:

    • Description: Small and cube-shaped.

    • Function: Provide stability and support with little movement.

    • Examples: Carpals in the hand and tarsals in the foot.

    1. Irregular Bones:

    • Description: Varied structure, often with ridges or complex shapes.

    • Function: Protect integral parts of the body while allowing for a range of movements.

    • Examples: Vertebrae (protects spinal cord), pelvic bones (ilium, ischium, pubis).

    1. Sesamoid Bones:

    • Description: Small and round; develop within tendons.

    • Function: Reinforce tendons, add strength.

    • Examples: Patella (kneecap), small sesamoid bones found near joints of the hands and feet.

    • Note: Everyone has patellae, but not all individuals have sesamoid bones in other locations.

Bone Shapes

  • Summary: Each type of bone has a distinct shape and form that is directly related to its function in the body, contributing to the overall functionality of the skeleton.