Porth's Essentials of Pathophysiology, 4e

Disorders of the Skeletal System: Metabolic and 44 C h a p t e r

Metabolic Bone Disease Osteopenia Osteoporosis

Etiology and Pathogenesis Clinical Features

Osteomalacia and Rickets Osteomalacia Rickets Paget Disease

Etiology and Pathogenesis Clinical Features

Rheumatic Disorders Systemic Autoimmune Rheumatic Diseases Rheumatoid Arthritis

Rheumatic Disorders

Systemic Lupus Erythematosus Systemic Sclerosis/Scleroderma Seronegative Spondyloarthropathies Ankylosing Spondylitis

Reactive Arthritis Psoriatic Arthritis

T

Osteoarthritis

he skeletal system plays an essential role in mineral homeostasis and mobility. The bones of the skeletal system provide the basic framework that supports the body, protects its organs, and provides for movement. Joints hold the bones of the skeleton together, making movement possible. Bone is also one of the few tissues that normally undergo mineralization. It is a storehouse for 99% of the body’s calcium and 85% of its phospho- rus. This chapter focuses on two types of skeletal disor- ders: metabolic bone diseases, which produce a decrease in bone mass and mineralization, and joint disorders, which disrupt mobility. Metabolic Bone Disease Metabolic bone disease represents disorders of bone metabolism that result in structural effects on the skel- eton, including decreased bone density and diminished bone strength. The strength of bone is determined by its composition and structure. 1 It must be rigid enough to support the body, yet flexible enough to absorb energy by deforming, to shorten and widen when compressed, and to lengthen and narrow under tension without cracking. There are two types of bone: cortical and trabecu- lar. Cortical or compact bone is composed of densely packed layers of mineralized collagen; it provides rigid- ity and is the major component of tubular bones (see Chapter 42, Fig. 42-1). Trabecular or cancellous bone is spongy on cross-section; it provides strength and elastic- ity, and constitutes the major part of axial skeletal struc- tures such as the vertebrae. Disorders in which cortical bone is defective or reduced in mass lead to fractures of the long bones, whereas those of cancellous bone lead preferentially to vertebral fractures.

Etiology and Pathogenesis Clinical Features Crystal-Induced Arthropathies Gout Rheumatic Diseases in Children and the Elderly Rheumatic Diseases in Children Juvenile Idiopathic Arthritis Juvenile Spondyloarthropathies Juvenile Dermatomyositis Rheumatic Diseases in the Elderly Osteoarthritis Rheumatoid Arthritis Crystal-Induced Arthropathies Polymyalgia Rheumatica Management of Rheumatic Diseases in the Elderly

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