Introduction to Dermatology

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Dermatology is the medical science of disorders of the skin. Often skin lesions and disorders are markers of internal disease and mirror the processes occurring within the body. Dermatology has been called "a window through which to see the entire body." As such an understanding of Dermatology is essential to the Internist.

Basics[edit]

Skin Anatomy[edit]

Skin consists of distinct layers. The most superficial (most exterior) layer is the epidermis. The epidermis is a stratified squamous epithelium. It has stacked layers of cells. Below the epidermis lies the dermis and below that we find the subcutaneous fat, or subcutis.

Epidermis[edit]

The epidermis consists of stratified squamous epithelium. The "bricks and mortar" cells of the epidermis are keratinocytes. Interspersed among the keratinocytes, we also find melanocytes and other specialized cells, known as Merkel cells. The keratinocytes provide the structure and maintain the barrier function of the skin. Melanocytes make protective pigment. Merkel cell function is less certain.

Skin Function[edit]

The primary functions of skin include protection from physical injury, impermeability (keeping fluids out of your body, and keeping necessary fluids inside of your body), resistance to microbial penetration, and function as a sensory end organ.

The secondary functions of skin include:

  • Immune Functions
    • Dryness, desquamation, normal flora of bacteria
    • Antigen presenting cells such as Langerhans cells, Keratinocytes (immunoregulating cytokine), Epidermotropic T-Cells.
  • Solar and Heat Interactions
    • UV Radiation Protection (melanin)
    • Thermoregulation
    • Vitamin D Metabolism
  • Communication

Functional Adaptations of Skin[edit]

  • Hair
  • Nails
  • Eccrine sweat glands
  • Apocrine glands
  • Sebaceous glands

Cellular Components of Skin[edit]

  • Epidermis
    • Keratinocytes
    • Langerhans cells
    • Melanocytes
    • Merkel cells
    • Lymphocytes
  • Dermis
    • Fibroblasts
    • Connective tissue
    • Extracellular proteins
    • Matrix
    • Endothelial cells
    • Mononuclear cells
    • Nerves and Neural organs
  • Hypodermis
    • Connective tissue
    • Adipocytes
    • Endothelial cells

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