Anatomy & Physiology
The Skeletal System- Part 4

JOINTS
 aka Articulations
 2 Functions:
1.
Hold Bones Together
2.
Allows otherwise rigid skeleton to have some flexibility

Classification of Joints
 Functionally
 Named according to how much movement allowed @ joint
 Structurally
 Named according to presence of fibrous tissue, cartilage, or a joint cavity separate the articulated bones

Functional Joints
 Synarthrosis
 Immovable joints
 Skull bones
 Amphiarthrosis
 Slightly movable joints
 Symphysis pubis
 Diarthrosis
 Freely movable joints
 Ball & Socket or Hinge Joints

Structural Joints
1.
Fibrous Joints
2.


Bones united by fibrous tissue
Joint connecting distal tibia & fibula
Cartilaginous Joints
3.


Bone ends connected by cartilage
Pubic symphysis
Synovial Joints
 Articulating ends of bone separated by joint cavity

4 Features of Synovial Joints
1.
Articular Cartilage
2.
 Hyaline cartilage covers ends of bones
Fibrous Articular Capsule
3.


Joint surfaces enclosed by capsule of fibrous CT
Capsule lined by synovial membrane
Joint Cavity
4.
 Contains synovial fluid
Reinforcing Ligaments
 Reinforce fibrous articular capsule

Types of Synovial Joints
1.



PLANE JOINT
Articular surfaces flat
Allow gliding movement (w/out rotation)
Example: intercarpal joints of wrist & ankle

Types of Synovial Joints
2. HINGE JOINT
 cylindrical end of bone fits into trough-shaped surface of another bone
 Angular movement allowed in 1 plane
 Examples: elbow, knee, interphalangeal joints

Types of Synovial Joints
3. PIVOT JOINT
 Rounded end of 1 bone fits into sleeve or ring of another bone
 allows 1 bone to rotate along its long axis
 Example: joint between atlas & dens of axis

Types of Synovial Joints
4.CONDYLOID JOINT
 “knuckle-like”
 Egg-shaped end of 1 bone fits into oval concavity in another bone
 Allows for moving bone to travel side-to-side & back-and-forth but cannot rotate along its long axis
 Example: metacarpophalangeal joint

4. CONDYLOID JOINT

Types of Synovial Joints
5. SADDLE JOINTS
 Each articular surface has convex & concave areas
 Same movements as condyloid joints
 Example: twiddling your thumbs

Types of Synovial Joints
6. BALL & SOCKET JOINTS
 Spherical head of 1 bone fits into a round socket formed by 1 or more bones
 Allows movement is 3 dimensions(most freely moving of synovial joints)

SPRAINS
 Ligaments or tendons reinforcing a joint are damaged by excessive stretching or tearing
 Both have poor blood supply so heal slowly

ARTHRITIS
 “inflammation of a joint”
 General term for >100 different diseases
 Most wide-spread, disabling disease in USA
 Onset: same symptoms: joint stiffness & swelling
 Synovial membrane inflammed  thickens  less synovial fluid  increased friction

Rheumatoid Arthritis
 Autoimmune disorder
 Adult onset or Juvenile onset
 Women 3x more often than men
 Any synovial joint could be affected, often symmetrical involvement
 disfiguring

Rheumatoid Arthritis

Osteoarthritis
 Most common form of arthritis
 Chronic degenerative condition: “wear-andtear”
 Affects articular cartilage (eventually breaks down)  increased friction  bone spurs develop  restricts movement

Osteoarthritis