1. Chapter 8
The Joints
Part A

2. Objectives: Classify the types of joints in the body
Give examples for the different types of joints
Label the parts of a typical diarthrotic joint
List types of diarthrotic joints with examples
List and identify the types of movement allowed by diarthrotic joints

3. Joints (Articulations)
Are the weakest parts of the skeleton
Articulation:
Site where two or more bones meet
Functions of joints
Hold the skeleton together
Give the skeleton mobility

4. Classification of Joints:
Joints are classified according to:
Structure
Function
Structural classification:
Based upon:
Material binding bones together
Presence or absence of a joint cavity
Functional classification:
The amount of movement allowed by the joint

5. Structural and Functional Classes of Joints:
Structural classes of joints include:
Fibrous
Cartilaginous
Synovial
Functional classes of joints include:
Synarthroses (immovable )
Amphiarthroses (slightly movable)
Diarthroses (freely movable)

6. Joints Functional Structural Diarthro. Synarthro. Amphiarthro. Fibrous
Cartilage
Synovial
Sutures
Symphysis
Gomphoses
Synchondroses
Syndesmoses

7. Structural Joints: Fibrous
Binding material:
Fibrous tissues join bones together
Presence of cavity:
No joint cavity is present
Movement:
Most are immovable
Types:
Sutures
Syndesmoses
Gomphoses

8. Fibrous Joints: Sutures
Occur:
Between the bones of the skull
Junctions:
Completely filled with short fibers of connective tissue
During youth:
Sutures bind bones tightly together, but allow growth
In middle age:
Fibrous tissue ossifies
Skull bones fuse
Sutures are then called synostoses
Movement:
Immovable (protective adaptation to the brain)

9. Fibrous Structural Joints: Sutures
Figure 8.1a

10. Fibrous Joints: Syndesmoses
Bones are connected by:
A ligament, a cord or band of fibrous tissue or
A ligament-like interosseous membrane
Movement:
Varies from immovable to slightly movable
Depends on fiber length
Examples include the connection between:
The distal ends of the tibia and fibula (short ligament)
The radius and ulna (Interosseous membrane)

11. Fibrous Structural Joints: Syndesmoses
Figure 8.1b

12. Fibrous Structural Joints: Syndesmoses (Radius & Ulna)
Figure 7.24

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

14. Tooth: Periodontal Ligament
Figure 23.11

15. Structural Cartilaginous Joints
Binding material:
Cartilage
Presence of cavity:
Lack a joint cavity
Types:
Synchondroses
Symphyses

16. Cartilaginous Joints: Synchondroses
A plate of hyaline cartilage unites bones
All synchondroses are synarthrotic (immovable)
Examples include:
Epiphyseal plates of children
First rib and sternum (manubrium) joint (costal cartilage)

17. Cartilaginous Joints: Synchondroses
Figure 8.2a, b

18. Cartilaginous Joints: Symphyses
Articular bone surfaces:
Covered with hyaline cartilage fused to an intervening pad of fibrocartilage
Are amphiarthrotic (slightly movable) joints
Designed for strength and flexibility
Examples:
Intervertebral joints
Pubic symphysis of the pelvis

19. Cartilaginous Joints: Symphyses
Figure 8.2c

20. Cartilaginous Joints: Symphyses
Figure 7.27a

21. Structural Synovial Joints
Binding material:
Hyaline cartilage on opposing bone surfaces
Components of the joint cavity
Presence of cavity:
Presence of a fluid-containing joint cavity
Movement:
All are freely movable
Diarthroses
Examples:
All limb joints
And most joints of the body

22. Synovial Joints: General Structure
All synovial joints have the following features:
Articular cartilage:
Thin spongy hyaline cartilage on bone surfaces
Joint (synovial) cavity:
Space containing small amount of synovial fluid
Two-layered articular (joint) capsule:
Fibrous capsule:
External; dense irregular c.t.; continuous with periosteum
Synovial membrane:
Internal; loose c. t.; covers capsule & internal non-hyaline cartilage surfaces

23. Synovial Joints: General Structure; cont’d.
Synovial fluid:
Blood filtrate
Produced by the synovial membrane capillaries
Reinforcing ligaments:
Capsular (intrinsic)
Extracapsular
Intracpsular

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

25. Synovial Joints: Friction-Reducing Structures
Bursae and Tendon Sheaths:
Not part of synovial joints
Closely associated with synovial joints
Bursae:
Flattened, fibrous sacs
Lined with synovial membranes
Contain a thin film of synovial fluid
Common where ligaments, muscles, skin, tendons, or bones rub together
Tendon sheath:
Elongated bursa
Wraps completely around a tendon

26. Synovial Joints: Friction-Reducing Structures
Figure 8.4

27. Synovial Joints: Stability
Stability is determined by three factors:
Articular surface shape (minor role):
Shallow or noncomplementary surfaces are misfits
Ligaments (minor role):
Unite bones
Prevent excessive or undesirable motion
Muscle tone (major role):
Low level of contractility in the relaxed state
Extremely important in reinforcing:
Shoulder & knee joints
Arches of the foot

28. Synovial Joints: Movement
Every skeletal muscle is attached to bone or other connective tissue structures
Attachment occurs at a minimum of two points
Muscle’s origin:
Attachment to the immovable bone
Muscle’s insertion:
Attachment to the movable bone

29. Synovial Joints: Movement
Movement occurs when:
Muscles contract across joints
Muscle insertion moves toward the muscle origin
Movement is described in directional term:
Around lines or axis
Along planes (transverse, frontal, or sagittal)

30. Range of Motion allowed by Synovial Joints
Nonaxial:
Slipping movements only
Uniaxial:
Movement in one plane
Biaxial:
Movement in two planes
Multiaxial:
Movement in or around all three planes