Bone development, classification and terminology

Bone Development

  • Understanding bone development and classification is critical as it relates to health and physiology.

Key Objectives

  • Describe different types of bone in the human body based on shape and function.

  • Review the physiological functions provided by bones.

  • Explore the mechanisms of bone development including flat bones of the skull and long bones of the limbs.

Structure of a Long Bone

  • Long bones are crucial for mobility and are structured to accommodate growth and development from childhood to adulthood.

  • Key characteristics of long bones:

    • Support and facilitate movement as levers.

    • Adapt in size and rigidity throughout life.

    • Have a dynamic structure that heals after fractures.

Key Functions of Bone

  • The skeletal system comprises bones, cartilage, ligaments, and tendons.

  • Bones function in various ways:

    • Support: Provides framework for the body.

    • Movement: Acts as levers for muscle action.

    • Protection: Shields vital organs (e.g., skull protecting the brain, ribs protecting lungs and heart).

    • Mineral Storage: Stores minerals like calcium and phosphorus.

    • Blood Cell Production: Produces blood cells in the bone marrow.

    • Energy Storage: Stores triglycerides in adipose tissue within the bone.

Composition of Bone

  • Bone is not merely a rigid structure; it comprises:

    • Cartilage: Flexible tissue aiding in joint movement and cushioning.

    • Connective tissues: Including ligaments and tendons that stabilize joints and connect muscles to bones.

    • Nervous system components: Ensuring the bone remains responsive to bodily needs.

    • Vascularization: Bones have arteries, veins, and lymphatics for nutrient and waste exchange.

Types of Bones

  1. Flat Bones

    • Functionally protective (e.g., skull, sternum, ribs).

    • Structure includes a hard outer shell with a spongy interior, providing strength and reduced weight.

  2. Irregular Bones

    • Have complex shapes that do not fit standard classifications (e.g., vertebrae, some facial bones).

  3. Short Bones

    • Cube-like structure that provides stability and support with limited motion (e.g., bones in wrists and ankles).

  4. Sesamoid Bones

    • Embedded within tendons (e.g., kneecap - patella).

    • Assist in force transmission and change of direction of tendon forces.

  5. Accessory Bones

    • Additional bones that may appear around the main skeletal system (e.g., small bones in the foot).

  6. Pneumatic Bones

    • Contain air-filled spaces (e.g., some bones in the skull) for structural lightweight but strong content; significant for reducing the overall weight of the head.

Bone Adaptation Over Lifespan

  • Increased flexibility and collagen present in children's bones compared to adults.

  • Bones become less flexible and can atrophy with age, resulting in higher fracture risk.

  • Importance of understanding these changes for maintaining bone health and preventing pathologies.