Which of these body parts does NOT produce melanin?
A.
Hair
B.
Nails
C.
Skin
D.
Iris
The Correct answer and Explanation is:
The correct answer is B. Nails.
Explanation
Melanin is a natural pigment produced by specialized cells called melanocytes, primarily found in the skin, hair, and the iris of the eye. It plays a crucial role in determining the color of these tissues and offers protection against ultraviolet (UV) radiation. Understanding where melanin is produced can help clarify why nails do not produce it.
Hair: Melanin is produced in the hair follicles, specifically by melanocytes located in the bulb of the hair. The type and amount of melanin influence the color of the hair, which can range from black and brown to blonde and red. The loss of melanin in hair can lead to graying as people age.
Skin: The skin is the primary site of melanin production. Melanocytes in the epidermis (the outermost layer of skin) produce melanin in response to UV exposure. This mechanism is part of the skin’s defense system against the harmful effects of UV rays, helping to absorb and dissipate radiation. Increased melanin production results in a darker skin tone, which is often referred to as tanning.
Iris: The iris, the colored part of the eye, also contains melanocytes that produce melanin. The amount and type of melanin in the iris determine the color of the eyes, with higher concentrations resulting in darker colors like brown, while lower levels yield lighter colors such as blue or green.
Nails: In contrast, nails do not contain melanocytes and therefore do not produce melanin. Instead, nails are composed of keratin, a protein that forms the hard structure of the nail. While nail color can be affected by the underlying blood vessels or external factors (such as nail polish), it does not contain melanin itself.
In summary, while hair, skin, and the iris all produce melanin through melanocytes, nails lack these cells and therefore do not produce melanin.