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.
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.