279
CHAPTER EIGHT
Joints of the Skeletal System
Synovial
membrane
Synovial
fluid
Tibia
Damage to
cartilage has
occurred
(a)
Normal knee
(b)
Osteoarthritic joint
Cartilage
Femur
Patella
FIGURE 8A
In osteoarthritis, an inherited defect in collagen, trauma, or prolonged wear and tear destroys joints.
The fibrous joints are the first to change, as the four
types of fontanels close the bony plates of the skull at two,
three, twelve, and eighteen to twenty-four months of age.
Other F
brous joints may accumulate bone matrix over time,
bringing bones closer together, even fusing them. ±ibrous
joints strengthen over a lifetime.
Synchondroses that connect epiphyses to diaphyses in
long bones disappear as the skeleton grows and develops.
Another synchondrosis is the joint that links the F
rst rib to
the manubrium (sternum). As water content decreases and
deposition of calcium salts increases, this cartilage stiffens.
Ligaments lose their elasticity as the collagen F bers become
more tightly cross-linked. Breathing may become labored,
and movement more restrained.
Aging also affects symphysis joints, which consist of a pad
of F brocartilage sandwiched between thin layers of hyaline
TABLE
8A
|
Dif
erent Types oF Arthritis
Some More-Common ±orms oF Arthritis
Type
Incidence in the United States
Osteoarthritis
20.7 million
Rheumatoid arthritis
2.1 million
Spondyloarthropathies
2.5 million
Some Less-Common ±orms oF Arthritis
Type
Incidence in the United States
Age oF Onset
Symptoms
Gout
1.6 million (85% male)
>40
Sudden onset of extreme pain and swelling of a large joint
Juvenile rheumatoid arthritis
100,000
<18
Joint stiF
ness, often in knee
Scleroderma
300,000
30–50
Skin hardens and thickens
Systemic lupus erythematosus
500,000 (>90% female)
teens–50s
±ever, weakness, upper body rash, joint pain
Kawasaki disease
Hundreds of cases in local
outbreaks
6 months–11 years
±ever, joint pain, red rash on palms and soles, heart
complications
Strep A infection
100,000
any age
Confusion, body aches, shock, low blood pressure, dizziness,
arthritis, pneumonia
Lyme disease
15,000
any age
Arthritis, malaise, neurologic and cardiac manifestations
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