Skin covers all our bodies, but its color varies from person to person. These cells and their allies--hair, sweat, and oil glands--form the first line of defense from the environment. The skin has three main layers with different functions.
How skin color is formed?
To see what gives skin its color, we need to focus on the outermost layer-- the epidermis-- and two important cell types: keratinocytes and melanocytes.
The keratinocytes are the cells that form the surface of the skin and are on the frontline for taking insults from the environment.
Deeper down in the epidermis, melanocytes are present which produce melanin pigment. So, Melanin is produced inside like spheres throughout the melanocyte. These are the melanosome that turns the amino acid tyrosine into melanin. The proportion of two main forms of melanin produced-- a reddish-yellow type versus a black-brown type; the total amount of melanin in each melanosome; and the number of melanosomes in the epidermis-- all vary from person to person and determine their skin color.
Melanosomes are the melanin factories inside melanocytes. But for melanin to do its job, melanosomes need to be transported to the keratinocytes via the melanocytes' long projections Inside the keratinocytes. So, Some melanosomes form a cap around the cell nucleus.
The melanin inside the melanosomes absorbs the ultraviolet energy from sunlight, reducing the amount of ultraviolet radiation that reaches the nucleus and, in particular, the DNA inside the nucleus. These UV radiations can cause mutations in DNA and thus that can lead to cancer. When ultraviolet radiation increases, melanin production increases, and more melanosomes are deliver to keratinocytes.
What really causes sunburns?
Sunburn is super easy. It just takes a few minutes sitting in the garden or on a beach, and then after a couple of days, the skin starts peeling off. Sunburns are not cause by heat.
Radiation in Sunlight:
Sunlight is made of a bunch of different types of radiation. One of them is infrared radiation which makes sunlight feel hot. But there’s also visible light that is called ultraviolet radiation. Because of this, we can see sunlight. Ultraviolet, or UV, radiation is what causes sunburn. It causes damage to skin cells by disrupting important molecules, like DNA.
Why your skin turns darker or tan:
When UV radiation hits your skin, pigments called melanin to absorb it, and shield your DNA from harm. Now, melanin is present in our skin cells and gives your skin a particular color. Melanin is form by special cells called melanocytes. They distribute the melanin to other cells called keratinocytes.
When your skin is expose to UV, the melanocytes increase the production of melanin. They transfer more melanin to the keratinocytes. This happens to vary in degrees based on your genetic makeup, that’s why your skin might turn darker, or tan, if you’re out in the sun for a while.
What happened to your skin in the presence of sunlight?
Some UV rays silently enter your skin and damage your DNA and this is happen in a few different ways.
- Sometimes the radiation will directly attack the DNA. It can damage it in just a trillionth of a second.
- UV rays can do something more dangerous. They can turn melanin against you. The radiation produces harmful molecules called free radicals in your cells, they excite an electron in your melanin.
- The melanin then hit your DNA and excites an electron there. This can cause the DNA to break.
Regardless of how it happens, once your cells are damage they start producing warning molecules, signaling that something bad is going on. If enough cells produce the signal, your body will create an inflammatory response. They are sending lots of different types of blood cells to the area to stop and repair the damage. And it causes redness and typically sees with sunburn, depending on how light your skin is.
How peeling of skin occurs?
Skin cells are shedding all the time without you noticing it. Stem cells are present in our skin that live for decades. The stem cells produce layers of keratinocytes. They fall off and are replace over time. When these cells are damage by UV then keratinocytes don’t mature properly. So instead of falling off, they all clump up and peel off together. Our body has enzymes that repair a lot of the DNA-damaged cells. But, it can’t permanently repair.
And if the damage isn’t fix in one of the stem cells, it is a real problem. When those cells replicate, they create a mutation at the site of the damage. And thus cause cells to become cancerous.
Remember, UV radiation can damage your DNA easily. So before going to be out in the sun for a while, make sure you’re covered up or wearing sunscreen.