Articulations and Joints Overview

Articulations

• 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.

Fibrous 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.

Cartilaginous Joints

• 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).

Synovial Joints

• 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.

Synovial Joint Types

• Plane or gliding: (ex. intercarpal joints).
• Hinge: (ex. elbow).
• Pivot: (ex. atlas/axis).
• Condyloid: (ex. metacarpalphalangeal joints).
• Saddle: (ex. metacarpal/carpal).
• Ball and socket: (ex. shoulder or hip).

Muscle Attachment and Movement

• Origin: The point of muscle attachment that is immobile.
• Insertion: The point of muscle attachment that moves.
• Contraction: The insertion moves towards the origin.

Synovial Joint Body Movements

• 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.

Foot Movements

• Inversion: Turning the feet medially (inward).
• Eversion: Lateral movement of the feet (outward).
• Dorsiflexion: Movement of the feet upward.
• Plantar flexion: Movement of the toes downward.

Joint Disorders

• Sprain: Excessive stretching or tearing of ligaments.
• Dislocation: Forceful removal of bones from their normal position.
• Adhesion: Connecting of bones at their surfaces by fibrous bands.
• Spur: Extraneous growth of bone tissue.

Explore the types of articulations and joints in the human body, including their structural and functional classifications. This quiz covers fibrous, cartilaginous, and synovial joints, as well as specific examples like sutures and syndesmoses. Test your knowledge on the different types of joints and their characteristics.