Skeletal System Structure, Function, and Extracellular Matrix

Components and Functions of the Skeletal System

The skeletal system consists of four primary components:

  • Bones
  • Cartilages
  • Tendons
  • Ligaments

The five major functions of the skeletal system are:

  1. Support
  2. Protection
  3. Movement
  4. Storage
  5. Blood cell production

Skeletal Divisions and Anatomy

Anterior and posterior views of the axial and appendicular skeleton

The skeletal system is divided into two major divisions:

  • Axial Skeleton: Includes the Skull, Mandible, Hyoid bone, Sternum, Ribs, Vertebral column, Sacrum, and Coccyx.
  • Appendicular Skeleton: Includes the Clavicle, Scapula, Humerus, Ulna, Radius, Carpal bones, Metacarpal bones, Phalanges, Hip bone, Femur, Patella, Tibia, Fibula, Tarsal bones, Metatarsal bones, and Phalanges.
  • Articulation and Movement: Involves articulation, joints, and types of movement.

Extracellular Matrix of Connective Tissues

Bone, cartilage, tendons, and ligaments are connective tissues whose physical characteristics are determined by their extracellular matrix.

  • General Composition: Contains collagen, ground substance, water, minerals, and other organic molecules.
  • Collagen: A tough, ropelike protein. High amounts of collagen fibers in tendons and ligaments make them very tough, similar to ropes or cables.
  • Proteoglycans: Large molecules consisting of many polysaccharides attached to and encircling core proteins. They form large aggregates and attract water.

Bone Extracellular Matrix

The extracellular matrix of bone is composed of collagen fibers and minerals, specifically calcium and phosphate.

  • Flexible Strength: Provided by ropelike collagen fibers.
  • Compression Strength: Provided by the mineral component, which allows for weight-bearing strength.
  • Hydroxyapatite: The primary mineral form in bone, composed of calcium phosphate crystals.