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Chapter 8

Chapter 8. Joints. Part A. Joints (Articulations). Weakest parts of the skeleton Articulation – site where two or more bones meet Functions Give the skeleton mobility Hold the skeleton together. Classification of Joints: Structural.

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Chapter 8

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  1. Chapter 8 Joints Part A

  2. Joints (Articulations) • Weakest parts of the skeleton • Articulation – site where two or more bones meet • Functions • Give the skeleton mobility • Hold the skeleton together

  3. Classification of Joints: Structural • Structural classification focuses on the material binding bones together and whether or not a joint cavity is present • The three structural classifications are: • Fibrous • Cartilaginous • Synovial

  4. Classification of Joints: Functional • Functional classification is based on the amount of movement allowed by the joint • The three functional class of joints are: • Synarthroses – immovable • Amphiarthroses – slightly movable • Diarthroses – freely movable

  5. Fibrous Structural Joints • The bones are jointed by fibrous tissues • There is no joint cavity • Most are immovable • There are three types – sutures, syndesmoses, and gomphoses Figure 8.1a

  6. Fibrous Structural Joints Figure 8.1b

  7. Fibrous Structural Joints: Sutures • Occur between the bones of the skull • Comprised of interlocking junctions completely filled with CT fibers • Bind bones tightly together, but allow for growth during youth • In middle age, skull bones fuse and are called synostoses

  8. Fibrous Structural Joints: Syndesmoses • Bones are connected by a fibrous tissue ligament • Movement varies from immovable to slightly variable • Examples include the connection between the tibia and fibula, and the radius and ulna

  9. Fibrous Structural Joints: Gomphoses • The peg-in-socket fibrous joint between a tooth and its alveolar socket • The fibrous connection is the periodontal ligament

  10. Cartilaginous Joints • Articulating bones are united by cartilage • Lack a joint cavity • Two types – synchondroses and symphyses Figure 8.2a

  11. Cartilaginous Joints Figure 8.2b

  12. Cartilaginous Joints Figure 8.2c

  13. Cartilaginous Joints: Synchondroses • A bar or plate of hyaline cartilage unites the bones • All synchondroses are synarthrotic • Examples include: • Epiphyseal plates of children • Joint between the costal cartilage of the first rib and the sternum

  14. Cartilaginous Joints: Symphyses • Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage • Amphiarthrotic joints designed for strength and flexibility • Examples include intervertebral joints and the pubic symphysis of the pelvis

  15. Synovial Joints • Those joints in which the articulating bones are separated by a fluid-containing joint cavity • All are freely movable diarthroses • Examples – all limb joints, and most joints of the body

  16. Synovial Joints: General Structure • Synovial joints all have the following: • Articular cartilage • Joint (synovial) cavity • Articular capsule • Synovial fluid • Reinforcing ligaments Figure 8.3a

  17. Synovial Joints: Friction-Reducing Structures • Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid • Common where ligaments, muscles, skin, tendons, or bones rub together • Tendon sheath – elongated bursa that wraps completely around a tendon

  18. Synovial Joints: Friction-Reducing Structures Figure 8.4a, b

  19. Synovial Joints: Stability • Stability is determined by: • Articular surfaces – shape determines what movements are possible • Ligaments – unite bones and prevent excessive or undesirable motion • Muscle tone is accomplished by: • Muscle tendons across joints are the most important stabilizing factor • Tendons are kept tight at all times by muscle tone

  20. Synovial Joints: Movement • Muscle attachment across a joint • Origin – attachment to the immovable bone • Insertion – attachment to the movable bone • Described as movement along transverse, frontal, or sagittal planes

  21. Synovial Joints: Range of Motion • Nonaxial – slipping movements only • Uniaxial – movement in one plane • Biaxial – movement in two planes • Multiaxial – movement in or around all three planes

  22. Gliding Movements • One flat bone surface glides or slips over another similar surface • Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae

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