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

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

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

4. Fibrous Structural Joints The bones are joined by fibrous tissues The bones are joined by fibrous tissues There is no joint cavity There is no joint cavity Most are immovable Most are immovable There are three types – sutures, syndesmoses, and gomphoses There are three types – sutures, syndesmoses, and gomphoses

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

6. Fibrous Structural Joints: Sutures Figure 8.1a

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

8. Fibrous Structural Joints: Syndesmoses Figure 8.1b

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

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

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

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

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

14. Synovial Joints: General Structure Synovial joints all have the following Synovial joints all have the following Articular cartilage Articular cartilage Joint (synovial) cavity Joint (synovial) cavity Articular capsule Articular capsule Synovial fluid Synovial fluid Reinforcing ligaments Reinforcing ligaments

15. Synovial Joints: General Structure Figure 8.3a, b

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

17. Synovial Joints: Friction- Reducing Structures Figure 8.4

18. Synovial Joints: Stability Stability is determined by: Stability is determined by: Articular surfaces – shape determines what movements are possible Articular surfaces – shape determines what movements are possible Ligaments – unite bones and prevent excessive or undesirable motion Ligaments – unite bones and prevent excessive or undesirable motion

19. Synovial Joints: Stability Muscle tone is accomplished by: Muscle tone is accomplished by: Muscle tendons across joints acting as stabilizing factors Muscle tendons across joints acting as stabilizing factors Tendons that are kept tight at all times by muscle tone Tendons that are kept tight at all times by muscle tone

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

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

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

23. Angular Movement Flexion — bending movement that decreases the angle of the joint Flexion — bending movement that decreases the angle of the joint Extension — reverse of flexion; joint angle is increased Extension — reverse of flexion; joint angle is increased Dorsiflexion and plantar flexion — up and down movement of the foot Dorsiflexion and plantar flexion — up and down movement of the foot

24. Angular Movement Abduction — movement away from the midline Abduction — movement away from the midline Adduction — movement toward the midline Adduction — movement toward the midline Circumduction — movement describes a cone in space Circumduction — movement describes a cone in space

25. Gliding Movement Figure 8.5a

26. Angular Movement Figure 8.5b

27. Angular Movement Figure 8.5c, d

28. Angular Movement Figure 8.5e, f

29. Rotation The turning of a bone around its own long axis The turning of a bone around its own long axis Examples Examples Between first two vertebrae Between first two vertebrae Hip and shoulder joints Hip and shoulder joints Figure 8.5g

30. Special Movements Supination and pronation Supination and pronation Inversion and eversion Inversion and eversion Protraction and retraction Protraction and retraction Elevation and depression Elevation and depression Opposition Opposition

31. Special Movements Figure 8.6a

32. Special Movements Figure 8.6b

33. Special Movements Figure 8.6c

34. Special Movements Figure 8.6d

35. Special Movements Figure 8.6e