๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
INTRODUCTION
Most reviews of the anatomy and physiology of skin begin with detailed descriptions of cellular composition, structural proteins, and extracellular matrix. Since each of these topics is covered in subsequent sections of the textbook, this chapter will briefly introduce the cells and structures, with references to the appropriate chapters for further details. We will reverse the conventional approach by examining diseases that illustrate the function of the skin in the context of the cells and structures that sustain it. This method is derived from the assertion that the structure and function of the skin are best illustrated by disease. The strength of this alternative approach may be seen in clinical vignettes easily recognized by those who care for patients with skin disease:
โa 70-year-old man with skin phototype I who works outdoors develops a lentigo maligna melanoma of the face
โa 16-year-old boy with hypohidrotic ectodermal dysplasia suffers a heatstroke while competing in outdoor athletics in Texas
โtoxic epidermal necrolysis due to trimethoprimโsulfamethoxazole develops in a 40-year-old woman, leading to dehydration and sepsis
โnumerous squamous cell carcinomas arise on the face and extensor forearms of a renal transplant recipient with significant cumulative sun exposure
โlinear eruption of grouped vesicles due to varicellaโzoster virus develops on the left flank of a young man with HIV infection These patients and their diseases illustrate at least four of the functions of the skin: photoprotection, thermoregulation, barrier formation, and immunologic protection.