Functional Classes of Joints

Functional Classes of Joints

1. Fibrous Joints

   • - United by fibrous connective tissue - Have no joint cavity - Move little or none
   • Sutures
     • - Opposing bone is interdigitate - Periosteum of one bone is continuous with the periosteum of the other - Sutural Ligament: Consists of two periostea & dense fibrous connective tissue in between - In adults, may ossify completely: Synostosis - Fontanels: Membranous areas in the suture between bones
   • Syndesmoses
     • - Bones are farther apart and joined by ligaments. - Some movement may occur
   • Gomphoses
     • - Pegs that fit into sockets - Periodontal Ligaments: Hold teeth in place - Inflammations: Gingivitis: Inflammation of the gums, if untreated may lead to periodontal disease (may destroy the periodontal ligaments and bone)

2. Cartilaginous Joints

   • Synchondroses
     • Hyaline Cartilage
       • - Little or no movement - Are temporary and replaced by synostoses, are permanent, and develop into synovial joints
   • Symphyses
     • Fibrocartilage
       • - Slightly movable

3. Synovial

   • - Contain synovial fluid - Allow considerable movement - Most joints that unite bones of appendicular skeleton
   • Structure
     • Capsule
       • Nerves in the capsule help the brain to know position of the joints. (Proprioception)
       • Fibrous Capsule
         • Dense irregular connective tissue, continuous with fibrous layer of the periosteum. Portions may thicken to form ligaments
       • Synovial Membrane
         • Membrane lines inside of joint capsule except at actual articulation of articular cartilages. It is thin, delicate and sometimes separated from fibrous capsule by areolar connective tissue and fat, sometimes merged with fibrous capsule. Secretes synovial fluid. Synovial Fluid: Complex mixture of polysaccharides, proteins, fat and phagocytic cells.
     • Joint Cavity
       • Encloses articular surface
     • Articular Cartilage
       • Hyaline; provides smooth surface. No blood vessels or nerves. Receives nutrients from nearby blood vessels and synovial fluid.
   • Accessory Structures
     • Bursae
       • Pockets of synovial membrane and fluid that extend from the joint. Found in areas of friction.
     • Menisci
       • Fibrocartilaginous pads in the knee
     • Ligaments and Tendons
       • Stabilization
     • Articular Discs
       • Temperomandibular, sternoclavicular, acromioclavicular
     • Tendon Sheaths
       • Synovial sacs that surround tendons as they pass near or over bone.
   • Types
     • Multiaxial
       • Occurring around several axes.
     • Biaxial
       • Occurring around two axes at right angles to each other
     • Uniaxial
       • Occurring around one axis