Anoka-Ramsey Community College 2

Overview of Cartilage and Skeletal Structure

Cartilage Characteristics

  • Resilience: Cartilage is highly resilient, allowing it to stretch, twist, and return to its original shape.

  • Lack of Blood Supply and Nerves: Cartilage does not have an internal blood supply or nerves to prevent damage during movement and pressure. Nutrients are supplied via blood vessels in the surrounding perichondrium.

  • Perichondrium: Dense connective tissue that surrounds cartilage, providing shape and resisting outward expansion under pressure.

Types of Cartilage

  1. Hyaline Cartilage:

    • Most abundant type in the body.

    • Composed of collagen fibers.

    • Found at:

      • Joint surfaces (articular cartilage).

      • Connecting ribs to sternum (costal cartilage).

      • Respiratory structures like the larynx and nasal cartilage.

  2. Elastic Cartilage:

    • Contains elastic fibers, giving it more flexibility and spring.

    • Found in:

      • External ear.

      • Epiglottis (flap protecting the windpipe during swallowing).

  3. Fibrocartilage:

    • Contains thick collagen fibers making it strong and tough.

    • Found in:

      • Intervertebral discs.

      • Menisci of the knee (joint pads).

      • Pubic symphysis (juncture of pelvic bones).

Growth of Cartilage

  • Appositional Growth: Growth from the outside, adding new layers of cartilage.

  • Interstitial Growth: Growth from within through cell division of chondrocytes and expansion of the extracellular matrix.

Functions of Bones

  1. Support: Provides a structural framework for the body and supports soft organs.

  2. Protection: Encases vital organs (e.g., skull protects the brain, rib cage protects thoracic organs).

  3. Movement: Muscles contract to move bones at joints.

  4. Mineral Storage: Bones store minerals such as calcium and phosphorus for strength and physiological processes.

  5. Blood Cell Production: Bone marrow within bones produces blood cells (hematopoiesis).

  6. Energy Storage: Stores fats as yellow marrow, providing energy reserves.

  7. Hormone Production: Bones produce hormones like osteocalcin that help regulate blood sugar and metabolism.

Structure of Bone

Bone Composition

  • Compact Bone: Dense outer layer of a bone, providing structural strength.

  • Spongy Bone: Inside structure of bone, with a porous appearance filled with trabeculae that provide support but are lighter.

  • Marrow Cavity: Hollow area within long bones containing bone marrow.

Types of Bone Based on Shape

  1. Long Bones: Longer than wide (e.g., femur, humerus).

  2. Short Bones: Cube-shaped similar in height and width (e.g., wrist and ankle bones).

  3. Flat Bones: Thin and flat, often with a slight curve (e.g., skull bones, sternum).

  4. Irregular Bones: Complex shapes that do not fit into other categories (e.g., vertebrae).

Growth and Development of Bones

  • Diaphysis: Shaft of a long bone, typically hollow and surrounded by compact bone.

  • Epiphysis: Ends of long bones, where articulation occurs at joints.

  • Epiphyseal Plate: Growth plate allowing for lengthening of bones, which changes to the epiphyseal line after growth ceases.

Bone Anatomy at Various Levels

  • Naked Eye: Identifying compact and spongy bone.

  • Microscope: Observing cell types like osteoblasts (build bone), osteocytes (maintain bone), and osteoclasts (breakdown bone).

Cellular Composition of Bone

  • Osteogenic Cells: Stem cells that can divide and become other bone cells.

  • Osteoblasts: Build bone by secreting the bone matrix (osteoid).

  • Osteocytes: Mature bone cells that maintain the bone tissue.

  • Osteoclasts: Break down bone tissue to release minerals into the bloodstream.

  • Bone Lining Cells: Line the surfaces of bones, maintaining the matrix.

Conclusion

Bones are dynamic organs that play vital roles in support, movement, storage of minerals and fat, protection, blood cell production, and hormone regulation, built from complex cellular structures and various types of tissues.