Pigmentation in humans ( melanin cells )

1. Pigmentation in humans (melanin cells) Presented by:- TsheringYangden Aitasingh Singer Myself

2. Different colours of human

3. Outline • Introduction • Location of melanin • Types • Structures • Functions • How does it synthesize • How does it distribute • Problems and risks of pigmentation

4. Introduction • Pigmentation is defined as the deposition of pigment in animals, plants or human beings. • Human beings come in a glorious spectrum of different colors: light, dark, plain or freckly skin; black, brunette, blond, auburn, and white hair; and eyes that are blue, hazel, green, amber and brown, to name just a few. • It’s amazing to realize that most of this color is attributed to a single class of pigments: the melanins.

5. Location of melanin • In humans, melanin is found in hair, the pigmented tissue underlying the iris of the eye, and the stria vascularis of the inner ear. In the brain, tissues with melanin include the medulla and zona reticularis of the adrenal gland, and pigment-bearing neurons within areas of the brainstem, such as the locus coeruleus and the substantia nigra. • Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is triggered by an enzyme called tyrosinase, which creates the color of skin, eyes, and hair shades.

6. Melanocyte Melanin pigment

7. Types of melanin • Melanocytes produce two types of melanin: • Pheomelanin (red):- is also found in hair and skin and is both in lighter-skinned humans and darker skinned humans. Pheomelanin imparts a pink to red hue and, thus is found in particularly large quantities in red hair. • Eumelanin (very dark brown):-is found in hair, areola, and skin, and the hair colors grey, black, yellow, and brown. In humans, it is more abundant in people with dark skin. • There are two different types of eumelanin. The two types are black eumelanin and brown eumelanin, with black melanin being darker than brown. Black eumelanin is mostly in non-Europeans and aged Europeans, while brown eumelanin is in mostly young Europeans.

8. Structure of melanin cells

9. Functions • Eumelanin:- is a black or brown pigment, and is mainly concerned with the protection of the skin by absorbing incoming UV radiation. This protective ability warrants melanin to be termed a photoprotectant (a substance capable of providing protection against radiation from the sun). • Pheomelanin:- is a reddish pigment, a very weak absorptive of UV radiation, further it also acts as a photosensitizer (makes your skin sensitive to light), where it increases sun sensitivity and skin ageing.

10. Deposition of melanocytes

11. Synthesizing of melanin • Melanin is formed in specialized cells, the melanocytes, which arise in the neural crest of the embryo and subsequently migrate to many sites in the body. • Melanocytes are especially abundant in the basal layer of the epidermis and underlying dermis and are responsible for the pigmentation of the skin. • Melanin is synthesized in these cells( melanosomes, small structures within the melanocyte cells) by the action of the enzyme tyrosinase, which catalyzes the oxidation of the amino acid tyrosine to dihydroxyphenylalanine (DOPA) and to dopa quinone. • Further elaboration of melanin occurs from these intermediates. It is a polymer which does not occur free but is invariably complexed with structural protein.

12. Distribution of melanin • The concentration of melanin, as well as its depth distribution, is strongly affected by ultraviolet radiation. • In un-tanned skin, melanin pigments are found only in the basal layer of the epidermis, while in tanned skin it is distributed throughout the epidermis. So far, mainly the amount of melanin, and not its distribution, has been considered in view of skin photobiology.

13. Problems and risks of pigmentation • These are the problems and risks of pigmentation