Introduction to Musculoskeletal Anatomy

Skeletal System Overview

• The skeletal system consists of bones, cartilages, and joints
• Functions: support, protect, allow movement, storage, and blood cell formation

Bone Functions

• Support: provides internal framework that supports the body and cradles its soft organs
• Protect: protects soft body organs
• Allow movement: allows movement through muscles and bones as levers
• Storage: stores minerals (calcium and phosphorus) and produces blood cells in bone marrow

Bone Classification by Shape

• Long bones: longer than they are wide, with a shaft and enlarged ends (e.g., bones of the limbs, except ankle bones)
• Flat bones: thin, flattened, and curved (e.g., most bones of the skull, ribs, and sternum)
• Short bones: cube-shaped (e.g., bones of the wrist and ankle, sesamoid bone in a tendon)
• Irregular bones: bones that do not fit into one of the preceding categories (e.g., vertebrae)

Joints

• Definition: site where two or more bones meet
• Function: hold bones together and provide mobility

Joint Classification

Functional Classification

• Synarthroses: immovable joints
• Amphiarthroses: slightly movable joints
• Diarthroses: freely movable joints

Structural Classification

• Fibrous joints: united via fibrous tissue (e.g., sutures in the skull, gomphoses)
• Cartilaginous joints: united via cartilage (e.g., synchondroses, symphyses)
• Synovial joints: united via a synovial membrane (e.g., plane, hinge, pivot, saddle, ball and socket)

Synovial Joints

• Characteristics: articular cartilage, articular capsule, synovial membrane, joint cavity with synovial fluid, and ligaments
• Types:
  • Plane joint: flat articular surfaces, no gliding or rotation (e.g., intercarpal joints)
  • Hinge joint: cylindrical end of one bone fits into a trough-shaped surface on another bone, uniaxial (e.g., elbow joint, ankle joint)
  • Pivot joint: rounded end of one bone fits into a sleeve or ring of bone, uniaxial (e.g., proximal radioulnar joint)
  • Saddle joint: allows movements in two axes, but not rotation (e.g., carpometacarpal joint of the thumb)
  • Ball and socket joint: allows movements in three axes, including rotation (e.g., shoulder joint, hip joint)