Overview
This lecture introduces the structure and function of joints in the human body, their classification, key features, and the types of movements they allow.
Classification of Joints
- Joints can be classified by function (mobility) or structure.
- Functionally, joints are: synarthroses (immovable), amphiarthroses (slightly movable), and diarthroses (freely movable).
- Structurally, joints are: fibrous (immovable), cartilaginous (slightly movable), and synovial (freely movable).
Fibrous Joints
- Fibrous joints contain dense connective tissue and no joint cavity.
- Types: sutures (skull), syndesmoses (ligament connection, e.g., tibia and fibula), gomphoses (tooth in socket).
- Sutures ossify with age, becoming synostoses.
Cartilaginous Joints
- Cartilaginous joints are connected by cartilage and lack a joint cavity.
- Synchondroses: contain hyaline cartilage, found in epiphyseal plates and first rib.
- Symphyses: contain fibrocartilage for shock absorption, found between vertebrae and in the pelvis.
Synovial Joints
- Synovial joints have a fluid-filled cavity, providing significant mobility.
- Features: articular cartilage, joint cavity with synovial fluid, synovial membrane, articular capsule, reinforcing ligaments, nerves, and blood vessels.
- May contain menisci (fibrocartilage discs), bursae (fluid sacs), and tendon sheaths (lubricate tendons).
Joint Movement and Terminology
- Muscles attach at an origin (immovable bone) and insertion (movable bone) to create movement at joints.
- Movement types: nonaxial (slipping), uniaxial (one plane), biaxial (two planes), multiaxial (three planes).
- Motion types: gliding (flat surfaces), angular (changes bone angle—flexion, extension, hyperextension, abduction, adduction, circumduction), and rotation (turning around axis).
- Special movements: supination/pronation (forearm), dorsiflexion/plantar flexion (foot), protraction/retraction (jaw).
Key Terms & Definitions
- Synarthroses — immovable joints.
- Amphiarthroses — slightly movable joints.
- Diarthroses — freely movable joints.
- Sutures — fibrous joints in the skull.
- Syndesmoses — fibrous joints joined by ligaments.
- Gomphoses — peg-in-socket fibrous joints (teeth).
- Synchondroses — cartilaginous joints with hyaline cartilage.
- Symphyses — cartilaginous joints with fibrocartilage.
- Synovial joints — freely movable joints with a fluid-filled cavity.
- Menisci — fibrocartilage pads in synovial joints.
- Bursae — fluid-filled sacs reducing friction in joints.
- Tendon sheaths — elongated bursae around tendons.
Action Items / Next Steps
- Review the types of joints and their features.
- Prepare for the next lecture on muscles attached to bones and joints.