Lecture on the Human Skeletal System

Introduction

Importance of understanding the skeletal system beyond simplifications (e.g., children’s song).
Skeletal system composed of bones, cartilage, and fibrous connective tissue.
Importance of joints in skeletal physiology.

Axial Skeleton:
- Composed of 80 midline bones.
- Includes skull, vertebral column, and thoracic cage.
- Skull: 8 cranial bones, 14 facial bones. Functions: protect brain, enable senses, facial structure.
- Vertebral Column: 33 irregular bones starting with the atlas vertebra. Supports upper body, protects spinal cord.
- Thoracic Cage: 12 pairs of ribs and sternum. Protects vital organs, provides muscle attachment.
Appendicular Skeleton:
- Includes upper and lower limbs, pectoral and pelvic girdles.
- Common structure: "one bone, two bones, lots of bones and digits."

Joints: Meeting places of bones, classified by material and movement.
Structural Classifications:
- Fibrous Joints: Dense fibrous tissue, mostly immovable (e.g., skull sutures).
- Cartilaginous Joints: United by cartilage, limited movement, no joint cavity.
- Synovial Joints: Freely movable, separated by fluid-filled joint cavity.
Functional Classifications:
- Synarthroses: No movement (e.g., cranial joints).
- Amphiarthroses: Slight movement (e.g., pubic symphysis).
- Diarthroses: Free movement (e.g., knee, elbow).

Gliding (Plane) Joints: Flat bone surfaces glide over one another.
Angular Movements: Alter angle between bones.
- Flexion: Decreases joint angle (e.g., bending an arm).
- Extension: Increases joint angle (e.g., straightening an arm).
- Hyperextension: Extending beyond normal limits.
- Abduction & Adduction: Moving away from or toward the body.
- Circumduction: Circular limb movement.
- Rotational Movements: Bone turns around its axis (e.g., shoulder rotation).