Lecture on Skeletal System and Joints

Introduction

• Instructor glad students are not in kindergarten.
• The skeleton song is reductive for college-level anatomy.
• Understanding the skeletal system involves more than just memorizing bones.

Components of the Skeletal System

• Bones, cartilage, and fibrous connective tissue.
• Joints: meeting places between two or more bones.
  • More joints than bones in the body.
  • Joints enable movement.

Importance of Joints

• Movement occurs when muscles contract across joints.
• Studying body movements helps understand bones and joints.

Major Divisions of the Skeleton

• Axial Skeleton
  • 80 midline bones: skull, vertebral column, thoracic cage.
  • Skull: 8 cranial bones, 14 facial bones.
  • Vertebral column: 33 vertebrae.
  • Thoracic cage: 12 pairs of ribs, sternum.
• Appendicular Skeleton
  • Upper and lower limbs.
  • Pectoral and pelvic girdles.
  • Limbs have a similar structure: one bone, two bones, lots of bones and digits.

Physiology of the Skeleton

• Focus on joints.
• Joints classified by material binding bones and their function.

Structural Classification of Joints

• Fibrous Joints
  • Dense fibrous connective tissue.
  • Mostly immovable (e.g., skull sutures).
• Cartilaginous Joints
  • Bones united by cartilage.
  • Limited movement, no joint cavity.
• Synovial Joints
  • Freely movable.
  • Separated by fluid-filled joint cavity with synovial fluid.
  • Six types enabling various movements.

Functional Classification of Joints

• Synarthroses: Immovable (e.g., cranial joints).
• Amphiarthroses: Slightly movable (e.g., pubic symphysis).
• Diarthroses: Fully movable (e.g., knee, elbow).

Types of Movement

• Gliding (Plane) Joints: Flat bone surfaces glide over one another.
• Angular Movements: Increase or decrease angle between bones.
  • Flexion: Decreases angle.
  • Extension: Increases angle.
  • Hyperextension: Extension beyond normal range.
  • Abduction: Movement away from midline.
  • Adduction: Movement toward midline.
  • Circumduction: Circular motion.
• Rotational Movements: Bone rotates around its axis (e.g., shoulder, hip).
• Special Movements: Unique to certain joints (e.g., thumb opposition, supination, pronation).

Conclusion

• Recap of axial and appendicular skeletons, joint classifications, and movements.
• Importance of understanding joint structure and function for practical applications.
• Special thanks to contributors and sponsors of the educational content.