Classification and Structure of Joints in the Skeleton

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. Table

6. 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

7. Fibrous Joints Figure 8.3

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

10. 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

11. Fibrous Structural Joints Figure 8.1b

12. Fibrous Structural Joints: Gomphoses gomph- = wedge-shaped bolt • The peg-in-socket fibrous joint between a tooth and its alveolar socket • The fibrous connection is the periodontal ligament

13. Fibrous Joints • Gomphosis • teeth anchored to the jaw with a periodontal ligament • Cone shaped socket • synarthrotic joint • The peg-in-socket fibrous joint between a tooth and its alveolar socket • The fibrous connection is the periodontal ligament Figure 8.4

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

16. Cartilaginous Joints Figure 8.2b

17. Cartilaginous Joints Figure 8.2c

18. 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

19. 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

20. 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

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

22. Illust - Knee Joint

24. 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

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

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

27. 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

28. 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

29. 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

30. Chapter 8 Movements Part B

31. Angular Movement • Flexion • Extension • Dorsiflexion and plantar flexion of the foot • Abduction • Adduction • Circumduction Figure 8.5a

32. Angular Movement Figure 8.5b

33. Angular Movement Figure 8.5c, d

34. Angular Movement Figure 8.5e, f

35. Rotation • The turning of a bone around its own long axis • Examples: • Between first two vertebrae (C1 & C2) • Hip and shoulder joints Figure 8.5g

36. Special Movements • Supination and pronation • Inversion and eversion • Protraction and retraction • Elevation and depression • Opposition Figure 8.6a

37. Special Movements Figure 8.6b

38. Special Movements Figure 8.6c

39. Special Movements Figure 8.6d

40. Special Movements Figure 8.6e

41. Chapter 8 Types of Synovial Joints

43. Types of Synovial Joints • Plane joints • Articular surfaces are essentially flat • Allow only slipping or gliding movements • Only examples of nonaxial joints Figure 8.7a

44. Types of Synovial Joints • Hinge joints • Cylindrical projections of one bone fits into a trough-shaped surface on another • Motion is along a single plane • Uniaxial joints permit flexion and extension only • Examples: elbow and interphalangeal joints Figure 8.7b

45. Pivot Joints • Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another • Only uniaxial movement allowed • Examples: joint between the axis and the dens, and the proximal radioulnar joint Figure 8.7c

46. Condyloid, or Ellipsoidal, Joints • Oval articular surface of one bone fits into a complementary depression in another • Both articular surfaces are oval • Biaxial joints permit all angular motions • Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints Figure 8.7d

47. Saddle Joints • Similar to condyloid joints but with greater movement • Each articular surface has both a concave and a convex surface • Example: carpometacarpal joint of the thumb Figure 8.7e

48. Ball-and-Socket Joints • A spherical or hemispherical head of one bone articulates with a cuplike socket of another • Multiaxial joints permit the most freely moving synovial joints • Examples: shoulder and hip joints Figure 8.7f

49. Synovial Joints: Shoulder (Glenohumeral) • Ball-and-socket joint in which stability is sacrificed to obtain greater freedom of movement • Head of humerus articulates with the glenoid fossa of the scapula

50. Synovial Joints: Shoulder Stability • Weak stability is maintained by: • Thin, loose joint capsule • Four ligaments – coracohumeral, and three glenohumeral • Tendon of the long head of biceps, which travels through the intertubercular groove and secures the humerus to the glenoid cavity • Rotator cuff (four tendons) encircles the shoulder joint and blends with the articular capsule