Overview
This lecture introduces joints (articulations) in the skeletal system, their classification by structure and function, and details the major types of synovial joints and their movements.
Joint Classification
- Joints connect two bones and allow movement, provide strength, or protect structures.
- Structural classification includes fibrous (collagen fibers), cartilaginous (cartilage), and synovial (synovial cavity with fluid) joints.
- Functional classification includes synarthrosis (immovable), amphiarthrosis (slightly movable), and diarthrosis (freely movable).
Synarthrosis (Immovable Joints)
- Fibrous synarthrosis: sutures of the skull, gomphosis (teeth in maxilla/mandible).
- Cartilaginous synarthrosis: synchondrosis (sternum and first rib, epiphyseal plates).
- Synostosis: ossified joint (e.g., frontal bone of the skull, fused epiphyseal plate).
Amphiarthrosis (Slightly Movable Joints)
- Fibrous amphiarthrosis: syndesmosis (distal tibiofibular joint).
- Cartilaginous amphiarthrosis: symphysis (pubic symphysis, intervertebral discs).
Diarthrosis (Freely Movable Joints / Synovial Joints)
- All synovial joints are diarthrosis; they have cavities filled with synovial fluid.
- Structures include articular cartilage, synovial membrane, joint cavity, ligaments, nerves, and blood vessels.
- Special structures: menisci (fibrocartilage pads), fat pads, ligaments (bone to bone), tendons (muscle to bone), bursae (fluid sacs reducing friction).
Types of Synovial Joints & Movements
- Plane (Gliding): flat surfaces slide (carpals in wrist, sacroiliac joint).
- Hinge: uniaxial movement (elbow, knee, interphalangeal joints).
- Pivot: uniaxial rotation (C1-C2 vertebrae, proximal radioulnar joint).
- Condylar: biaxial movement (radiocarpal joint, metacarpophalangeal joints).
- Saddle: biaxial movement (thumb’s carpometacarpal joint, sternoclavicular joint).
- Ball and Socket: multiaxial movement (shoulder, hip joints).
Key Terms & Definitions
- Joint (Articulation) — location where two bones meet.
- Fibrous Joint — joint connected by collagen fibers.
- Cartilaginous Joint — joint connected by cartilage.
- Synovial Joint — joint with a synovial cavity filled with fluid.
- Synarthrosis — immovable joint.
- Amphiarthrosis — slightly movable joint.
- Diarthrosis — freely movable joint.
- Articular Cartilage — hyaline cartilage covering bone ends at synovial joints.
- Meniscus — fibrocartilage pad in synovial joints.
- Ligament — tissue connecting bone to bone.
- Tendon — tissue connecting muscle to bone.
- Bursa — fluid-filled sac reducing joint friction.
Action Items / Next Steps
- Review specific joint anatomy and types of body movements in the next mini lectures.
- Study joint examples and their structural and functional classifications.
- Prepare for upcoming material on the muscular system.