Articulations and Joints Overview

Study Notes

An articulation is a joint, allowing for flexibility and holding bones together.
Fibrous, Cartilaginous, and Synovial - These are the structural classifications of joints.
Synarthroses, Amphiarthroses, and Diarthroses - These are the functional classifications of joints.

Held together by fibrous tissue, most are synarthrotic (immovable).
Sutures are joints where bones interlock with short fibers, found in the skull.
Syndesmoses are joints with bones connected by short ligaments, slightly movable, such as the tibia and fibula at the distal joint.
A Gomphosis is the joint holding teeth in the mandible, using the periodontal ligament.

Articulating bones are connected by cartilage, have no joint cavity, mostly amphiarthrotic (slightly movable).
- Symphyses contain bones connected by a flat disc of fibrocartilage (ex. pubic symphysis).
- Synchondroses are bones connected by hyaline cartilage (ex. epiphyseal plates in children).

Bones are separated by a joint cavity filled with synovial fluid, diarthrotic (freely movable).
Characteristics of synovial joints:
- Articular Capsule: Two layers, a fibrous capsule and a synovial membrane that secretes synovial fluid.
- Articular cartilage: Hyaline cartilage covers the articulating bone surfaces.
- Ligaments: Hold bones of the joint together.
- Bursae: Fluid-filled sacs.
- Articular discs (ex. meniscus) can be present, acting as padding.

Flexion: Decreases the angle between the origin and the insertion.
Extension: Increases the angle between the origin and the insertion.
Abduction: Movement away from the midline.
Adduction: Movement towards the midline.
Rotation: Movement around the long axis of a bone.
Circumduction: Movement that makes an imaginary cone along the long axis of a bone.
Pronation: Turning the hand from the anatomical position, crossing the ulna and radius.
Supination: Returning the hand to the anatomical position, radius and ulna parallel.