Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath.
skin color adapts to intense sunlight irradiation to provide partial protection against the ultraviolet fraction which produces damage and thus mutations in the DNA of the skin cells.
The melanin in the skin is produced by melanocytes, which are found in the basal layer of the epidermis.
Although, in general, human beings possess a similar concentration of melanocytes in their skin, the melanocytes in some individuals and ethnic groups more frequently or less frequently express the melanin-producing genes, thereby conferring a greater or lesser concentration of skin melanin.
Some individual animals and humans have very little or no melanin in their bodies, a condition known as albinism.
There are many different types of melanin.
Black eumelanin is mostly in non-Europeans and aged Europeans, while brown eumelanin is in mostly young Europeans.
In general, people whose ancestors lived for long periods in the regions of the globe near the equator have larger quantities of eumelanin in their skins.
This makes their skins brown or black and protects them against high levels of exposure to the sun, which more frequently results in melanomas in lighter-skinned people.
Basically, the skin is comprised of two layers that cover a third fatty layer. These three layers differ in function, thickness, and strength.
The outer layer is called the epidermis; it is a tough protective layer that contains the melanin-producing melanocytes.
The second layer (located under the epidermis) is called the dermis; it contains nerve endings, sweat glands, oil glands, and hair follicles.
Under these two skin layers is a fatty layer of subcutaneous tissue, known as the subcutis or hypodermis.
The epidermis is the top layer of the skin. It is mostly made of flat cells known as squamous cells.
Under the squamous cells in the deepest part of the epidermis are round cells called basal cells.
Cells called melanocytes make the pigment (color) melanin found in skin and are located in the lower part of the epidermis.
The dermis lies beneath the epidermis.
It contains blood vessels, lymphatic vessels, and glands.
Some of these glands make sweat, which helps cool the body.
Other glands make sebum. Sebum is an oily substance that helps keep the skin from drying out.
The dermis is transparent. The dermis is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues.
The blood vessels in the dermis provide nourishment and waste removal for both dermal and epidermal cells.
Pigmentations: hemoglobin, melanin.
Light reflects off oil on the skin.
The theory of TRS (tissue reflectance spectroscopes) is based upon a simple anatomical model.
Light passes through the epidermis (melanin layer) and a plexus of blood vessels in the dermis (hemoglobin (Hb) layer) before being reflected off collagen in the lower dermis.
Melanin absorbs and converts forms of electromagnetic energy [light] to be used by the nervous system.
The darkness of the melanin means it is able to absorb.
The skin protects human from harmful ultraviolet (UV) radiation.
The body has the ability to use UV light from the sun to make Vitamin D.
As light passes through the skin's melanin layer it is converted into a substance called D3.
Light in the near infrared region (700 - 1000 nm) penetrates relatively deep into tissue when compared to visible light (450-700 nm) making the detection of deeper tissue structures, like hemoglobin, possible.