The
respiratory system is composed of the upper and lower respiratory tracts.
Together, the two tracts are responsible for ventilation (movement of
air in and out of the airways). The upper tract, known as the upper airway,
warms and filters inspired air so that the lower respiratory tract (the lungs)
can accomplish gas exchange. Gas exchange involves delivering oxygen to the
tissues through the bloodstream and expelling waste gases, such as carbon
dioxide, during expiration.
RHEUMATOID ARTHRITIS
Pathophysiology
RA is commonly used as the prototype for inflammatory
arthritis. The incidence rate is approximately 3%, with a two to three times
greater incidence in women (Ruddy et al., 2001). In RA, the autoimmune reaction
(Fig. 54-3) primarily occurs in the synovial tissue. Phagocytosis produces
enzymes within the joint. The enzymes break down collagen, causing edema,
proliferation of the synovial membrane, and ultimately pannus formation. Pannus
destroys cartilage and erodes the bone. The consequence is loss of articular
surfaces and joint motion. Muscle fibers undergo degenerative changes.
Tendon and ligament elasticity and contractile power are lost.
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