Skin : The Body's Barrier to Infection and Disease

The first identify the skin as a protective coverring for the internal organs was the famous pathologist Rudolph Virchow. It was decades later, that sceintists and physicians began to understand that the skin is a regulated wnvironment of cellular and molecular interactions which react to environmental stimuli.

Keratinocytes
The skin is a mosaic of different cell types. Histologically, the skin is formed by squamous epithelial cells, termed keratinocytes, ass they produce keratin protein. In addition, these cells play a role in protection, as they can produce cytokines, soluble molecules, which can recruit other cells, specifically white blood cells, in times of infection and stress. Melanocytes produce the pigment of our skin, and their proportion varies throughout the races.

Melanocytes
Melanocytes specifically produce melanin, a brown pigment, which they disperse to the lower cells of the skin, basal cells, and with maaturation, these cells move to the surface with the melanin granules in their cytoplasm. Melanin is the molecule which protects us against ultraviolet rays that are found within sunlight.

Langerhans Cells
Langerhans cells are epidermal dendritic cells, which take up foreign particles and present these to our immune system while they traffic to nearby lymph nodes.

Merkel Cells
There is also an extensive network of neural cells and axons within the skin. Merkel cells are believed to have endocrineas well as mechanoreceptor roles within the skin.

Adnexal Structures
Sweat glands play a vital role in body temperature homeostasis. Hair follicles for hair, as well as protecting the skins cell factories, by protecting the stem cells of the skin (the cells with regenerating capacity).