Chap 9--Joints

classified structurally (fibrous, cartilaginous, synovial) or functionally (synarthroses, amphiarthroses, or diarthroses).

Fibrous Joints

bones joined by fibrous tissue, no cavity in the joint. amount of movement depends on length of connecting fibers. Most synarthrotic.

Sutures-seams between bones in skull. In adults, synostoses.

Syndesmoses--bones connected by ligament or interosseous membrane (sheet like). Slight to lots of movement possible. Connection of radius/ulna by interosseus membrane example.

Gomphoses--tooth in socket by periodontal ligament

Cartilaginous Joints

No cavity. Bones linked by cartilage.

Synchondroses--bar/plate of hyaline cartilage unites bones--epiphyseal plates.

Symphyses--articular surfaces of bone covered w/hyaline cartilage which is fused to a pad of fibrocartilage. Shock absorption, limited movement. Pubic symphisis, intervertebral joints.

Synovial joints

Most joints. Fluid-containing cavity. Much movement possible.

5 Characteristics:

1. Articular hyaline cartilage
2. Joint cavity
3. articular capsule--2 layers around cavity--outer fibrous continuous w/periostea, inner synovial.
4. Synovial fluid--filtration from plasma, viscous. Lubes.
5. Reinforcing ligaments--usually intrinsic, formed from fibrous capsule. Can be found in capsule or deep to it.

Some have articular discs, some have fatty pads

Bursae and tendon sheaths, flattened fibrous sacs containing synovial fluid, are often found in association w/synovial joints.

Stability

depends on articular surfaces, ligaments, muscle tone (tendons passing over joint)most important.

Movements

• Nonaxial, uniaxial,biaxial, multiaxial.
• Gliding movements--2 flat bone surfaces gliding on each other.
• Angular movements--angle between bones changes
• Flexion--decreasing angle and brings 2 bones closer together
• Extension opposite of flexion. same joints
• Abduction--movement away from midline of body
• Adduction--opposite of abduction
• Circumduction--limb describes a cone.
• Rotation--bone turns on long axis.
• Special movements--pro- and re-traction, elevation anddepression, opposition.

Types of synovial joints.

Plane--intercarpal, intertarsal, gliding only

Hinge--convex projection into concavity, single plane motion-elbow an example

Pivot--rotation along long axis--atlas/axis

Condyloid--biaxial, oval protuberance and concavity. knuckles

Saddle--Both surfaces saddle shaped. thumb ball

Ball and socket--most freely moving. shoulder and hip

Injuries

Sprain-stretched or torn ligament.

Read up on injuries to joints.