Joints and Skeletal Articulations

1. Joints and Skeletal Articulations 5

2. Joints (Articulations) - know • Articulation – site where two or more bones meet • Functions of joints • Give the skeleton mobility • Hold the skeleton together • Joints are a weak part of the skeleton and are often injured

3. Classification of Joints: Structural - know • Structural classification focuses on the material binding bones together and whether or not a joint cavity is present • The three structural classifications are: • Fibrous (cranial bones) • Cartilaginous (ribs – sternum) • Synovial (knee)

4. Classification of Joints: Functional - know • Functional classification is based on the amount of movement allowed by the joint • The three functional classes of joints are: • Synarthroses – immovable (cranial bones) • Amphiarthroses – slightly movable (vertebrae) • Diarthroses – freely movable (knee) We will discuss joints based on structural classification:

5. 1. Fibrous Joints (structural classification) - know • The bones are joined by fibrous tissues • There is no joint cavity • Most are immovable There are three types – sutures, syndesmoses, and gomphoses

6. a. Fibrous Joints: Sutures - know • Occur between the bones of the skull • *Comprised of interlocking junctions completely filled with connective tissue fibers* • Bind bones tightly together, but allow for growth during youth • Skull bones fuse and are called synostoses • Begins as early as age 10-15, generally complete by age 30-50

7. Fibrous Structural Joints: Sutures - example Figure 8.1a

8. b. Fibrous Joints: Syndesmoses - know • *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 Joints: Syndesmoses - example Figure 8.1b

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

11. 2. Cartilaginous Joints (structural classification) - know • Articulating bones are united by cartilage • *Lack a joint cavity* • Two types – synchondroses and symphyses

12. a. Cartilaginous Joints: Synchondroses - understand • A bar or plate of hyaline cartilage unites the bones • All synchondroses are synarthrotic (immovable) • Examples include: • Epiphyseal plates of children • Joint between the costal cartilage of the 1st rib and the sternum

13. Cartilaginous Joints: Synchondroses - example Figure 8.2a, b

14. b. Cartilaginous Joints: Symphyses - understand • Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage • Amphiarthrotic (slightly movable) joints designed for strength and flexibility • Examples include intervertebral joints and the pubic symphysis of the pelvis (expansion in female for childbirth)

15. Cartilaginous Joints: Symphyses - example

16. 3. Synovial Joints (structural classification) - know • Most common • *Those joints in which the articulating bones are separated by a fluid-containing joint cavity* • All are diarthroses (freely movable) • Examples – all limb joints, and most joints of the body (regardless of size!)

17. Synovial Joints: General Structure - understand All synovial joints have: • Articular cartilage • Joint (synovial) cavity • Articular capsule • Synovial fluid • Reinforcing ligaments

18. Synovial Joints: General Structure - example Cadaver dissection

20. Synovial Joints: Friction-Reducing Structures - know These friction-reducing structures are found in synovial joints and are common where ligaments, muscles, skin, tendons, or bones rub together: • Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid • Tendon sheath – elongated bursa that wraps completely around a tendon

21. Synovial Joints: Friction-Reducing Structures – understand complexity

22. Synovial Joints: Stability - understand Stability is determined by: • Articular surfaces – shape determines what movements are possible • Ligaments – unite bones and prevent excessive or undesirable motion • Muscle tone • Tendons of muscles cross the joint and help stabilize it • The tendons are kept tight by muscle tone

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

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

25. 1. Gliding Movements - understand • 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

26. Angular Movement – know – (important slide!) • Flexion — bending movement that decreases the angle of the joint • Extension — reverse of flexion; joint angle is increased • Dorsiflexion and plantar flexion — up and down movement of the foot • Abduction — movement away from the midline • Adduction — movement toward the midline • Circumduction — movement describes a cone in space

27. Gliding Movement – know (be able to identify)

28. Angular Movement – know (be able to identify)

29. Angular Movement – know (be able to identify)

30. Angular Movement – know (be able to identify)

31. Rotation – know (be able to identify) • The turning of a bone around its own long axis • Examples • Between atlas and axis • Hip and shoulder joints

32. Special Movements – know (be able to identify) • Supination and pronation • Inversion and eversion • Protraction and retraction • Elevation and depression • Opposition

33. Special Movements – know (be able to identify)

34. Special Movements – know (be able to identify)

35. Special Movements – know (be able to identify) Figure 8.6c

36. Special Movements – know (be able to identify) Figure 8.6d

37. Special Movements – know (be able to identify)

38. How joints are classified Examples • Link to table of joints • Medical school site: Joints • Arthritis Foundation Website

39. Types of Joints: examples Various kinds of joints. Fibrous: A, syndesmosis (tibiofibular); B, suture (skull). Cartilaginous: C, symphysis (vertebral bodies); D, synchondrosis (first rib and sternum). Synovial: E, condyloid (wrist); F, gliding (radioulnar); G, hinge or ginglymus (elbow); H, ball and socket (hip); I, saddle (carpometacarpal of thumb); J, pivot (atlantoaxial).