Chapter 8

1. Chapter 8 Joints of the Skeletal System

2. Classification of Joints

3. Joints of the Skeletal System • Articulations • Functional junctions between bones • Bind parts of skeletal system together • Make bone growth possible • Permit parts of the skeleton to change shape during childbirth • Enable body to move in response to skeletal muscle contraction

4. Functional Classification Of Joints • Classification=based on the amount of movement allowed • 3 types: • Synarthroses = immovable joints • Example = sutures of skull • Amphiarthroses = slightly movable joints. • Example = intervertebral discs between vertebrae • Diarthroses = freely movable joints • Examples = joints of appendicular skeleton

5. Structural Classification Of Joints • Classification= Based on material, which joins bones • 3 types: • Fibrous • Cartilaginous • Synovial

6. Fibrous Joints • joints composed of fibrous tissue • no joint cavity is present • 3 types: • Syndesmosis • Suture • Gomphosis

7. Fibrous Joints cont. • Syndesmosis = cord of fibrous tissue called a ligament • amphiarthroses with "give" but no true movement • Example = distal tibiofibular joint

8. Fibrous Joints cont. • Sutures = short fibrous CT fibers • synarthroses • Only found in skull

9. Fibrous Joints cont. • Gomphosis = tooth within its bony socket (alveolar fossa) • short periodontal ligament

10. Cartilaginous Joints • joints composed of cartilage • no joint cavity • 2 types: • Synchondrosis • Symphysis

11. Cartilaginous Joints cont. • Synchondrosis = a plate of hyaline cartilage • sites of bone growth during youth • eventually ossify = synarthrotic • Examples: joint between the first rib and manubrium and the epiphyseal plate

12. Cartilaginous Joints cont. • Symphysis = pad or plate of fibrocartilage • compressible "shock absorber" • limited movement = amphiarthroses • Examples: intervertebral discs and symphysis pubis

13. Synovial Joints • = fluid-filled joint cavity • free movement = diarthrosis

14. General Structure Of A Synovial Joint • General Structure Of A Synovial Joint = 5 distinct features: 1. Articular cartilage = hyaline cartilage covers the surface of each bone 2. Joint cavity = a potential space between the two bones, filled with synovial fluid 3. Synovial fluid = viscous lubricating fluid within cavity • reduces friction between cartilages of 2 bones • provide lubrication • nourish cartilage • contain phagocytes

15. Synovial Joints cont. 4. Articular capsule = double layered capsule surrounding cavity: • External, tough flexible fibrous capsule (continuous with periosteum of the bones) • Synovial membrane = loose CT lining of fibrous capsule, that also covers all internal joint surfaces excluding hyaline cartilage 5. Reinforcing ligaments = ligaments that strengthen joint • Definition: A ligament joins a bone to another bone across a synovial joint • usually thickened portions of fibrous capsule (intrinsic or capsular)

16. General Structure of a Synovial Joint

17. Synovial Joints cont. • Other joint features: • fatty pads (hip & knee) • menisci or articular discs or that separate cavity into 2 compartments (knee, jaw, sternoclavicular)

18. Synovial Joints cont. • bursa = flattened fibrous sacs with a synovial membrane and fluid that act as "ball bearings" to prevent friction on adjacent structures during joint activity • cushion the movement of one body part over another; • located between skin and bone (where skin rubs over bone), and between muscle, tendons, ligaments and bone.

19. Types Of Synovial Joints • Ball-and-socket joints = most freely movable joints; all angular movement • The head of one bone fits into the socket of another • Examples = hip and shoulder • Condyloid joints = permit all angular motion, except rotation • Examples = wrists and knuckles

20. Types Of Synovial Joints cont. • Gliding joints = cartilaginous joints • Example = intervertebral discs • Hinge joints = permit flexion & extension only • Examples = elbow and knee

21. Types Of Synovial Joints cont. • Pivot joints = permit rotation • Example = first intervertebral joint (atlantoaxial joint) • Saddle joints = thumb

22. Types Of Joint Movements

23. Introduction • Origin = part of muscle attached to the immovable bone • Insertion = part of a muscle attached to the movable bone • When a muscle contracts across a joint, its insertion is pulled toward its origin

24. Three general types of movement Gliding movements = when flat bone surfaces glide or slide over one another • occur at cartilaginous joints • Examples = intervertebral discs and sternoclavicular joints Angular movements = changes in angles between bones • occur only at synovial joints

26. Movement cont. • Flexion = decreasing the angle between 2 bones. • Example = head toward chest • Dorsiflexion = bringing foot closer to shin • Plantar flexion = pointing one's toe (flexion toward the sole) • Extension = increasing the angle between 2 bones • Example = straightening a flexed neck • Hyperextension = increasing the angle greater than 180o

28. Movement cont. • Abduction = moving a limb away from the midline. • Example = raising arm or thigh laterally; • Adduction = moving a limb toward the midline

30. Movement cont. • Circumduction = moving a limb in a circular (cone-shaped) manner • Rotation = turning movement of a bone along its long axis. • Example = atlas over axis (i.e. “just say no”) • Example = shoulder and hip joint

32. Special Movements Special Movements = those at specific joints • supination/pronation = movements between the radius and ulna at the proximal radioulnar joint • thumb up = supination • thumb down = pronation • inversion/eversion = movement of foot • sole inward = inversion • sole out = eversion

34. Special Movements cont. • elevation/depression • shoulder shrug = elevation • mandible in opening mouth = depression • protraction/retraction • thrust forward = protraction • pull back = retraction

36. Shoulder joint • Shoulder joint (2 joints) • Ball and socket is the glenohumeral joint • joins Glenoid cavity and head of humerus • Syndesmosis is called the acromioclavicular joint • acromial end of clavicle and the acromion process of the scapula • Ball and socket is surrounded by many reinforcing ligaments and tendons collectively called the rotator cuff • Many bursa also lubricate the shoulder • Movement can occur in any angular plane

38. Elbow joint • (2 joints) • Hinge is between trochlea of humerus and trochlear notch of ulna • Gliding joint is between capitulum of humerus and head of radius • Very stable joint with many reinforcing ligaments • Only allows flexion and extension

40. Hip joint • (coxal joint) • Ball and socket between head of femur and acetabulum of coxa • Contains many large reinforcing ligaments • Allows same movements as shoulder, but with less range due to bony limitations

42. Knee • (3 joints) • Largest, most complex joint • Functions as a hinge even though 3 joints work together • Medial condyles of femur and tibia make one condyloid joint • Lateral condyles of femur and tibia make another condyloid joint • Patellar surface of femur and patella make a gliding joint • Flexion and extension with some slight rotation • Contains many reinforcing structures

43. Knee cont. • Menisci • medial meniscus • lateral meniscus • C-shaped fibrocartilage pads • Reshape the tibial condyles for a better fit • Absorb shock • Many bursae