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Human Skin: Layers, Function & Structure

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  • 0:06 Sunburns and Tans
  • 0:25 The Epidermis
  • 2:04 Types of Skin Cells
  • 6:14 The Dermis
  • 7:18 The Subcutis
  • 8:03 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will cover the three main layers of your skin, which includes the epidermis, dermis, and subcutis. In addition, we'll learn about other skin cells and tissue, such as adipose tissue, keratinocytes, melanocytes, and Merkel's cells.

Sunburns and Tans

If you're the type of person who loves to bake in the sun, then you've probably experienced something called a tan or sunburn. The sunburn and tan you may have acquired involved sunlight, certain layers of your skin, and the cells within those layers.

The Epidermis

You see, the sun's light rays travel through space, then through the Earth's atmosphere, and finally hit your skin as you lie on the beach sipping a non-alcoholic piña colada with a little umbrella sticking out of the glass.

The first, topmost, or superficial, layer of the skin the sun's rays hit is called the epidermis. Again, the epidermis is the outermost layer of the skin. The epidermis is itself made up of several layers. From outer to innermost, they are the:

  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale

The stratum lucidum layer of the epidermis is typically only found in certain body parts.
Stratum Lucidum

Do note, however, that the stratum lucidum is typically only found in places like the soles of your feet or the palms of your hand. Regardless, it's pretty easy to remember the exact order of the layers of the epidermis. Since we're on the topic of possible sunburns, the coolest mnemonic to remember the layers of the epidermis from top to bottom, or superficial to deepest, is:

'Come, Let's Get Sun Burn.'

Each word's first letter represents the first letter of each layer. In case you were wondering, the epidermis is actually the layer of skin that is primarily affected in most cases of sunburn and begins to peel off if damaged by the light's dangerous UV rays.

Types of Skin Cells

However, your skin isn't a weakling and does have a defense mechanism that tries to fight off dangerous ultraviolet rays found in sunlight. In the deepest layer of the epidermis, the stratum basale (which is also sometimes called the basal layer), are cells called melanocytes. These are cells that produce the pigment melanin. It is this substance, melanin, which determines the skin color of an individual. Those with larger amounts of melanin in their skin have darker skin, or their skin darkens with more exposure to sunlight.

Melanocytes in the basal layer of the epidermis produce the pigment melanin.
Melanocytes in Basal Layer

Basically, as the sunlight hits your skin, the light rays stimulate the production of melanin by melanocytes. Since the majority of melanin is called eumelanin, which is a brownish black color, your skin begins to darken as more melanin is produced. Keep in mind that this melanin isn't produced to give you a nice tan for aesthetic reasons, but instead, helps protect you from cancer-causing ultraviolet radiation found in the sunlight that is baking and peeling your skin off at the beach. At least the pale vampires who come out after twilight don't have to worry about this.

Pale vampires aside, your epidermis has other cells that are quite important. One type of these cells is called keratinocytes. Keratinocytes are cells that eventually die in order to comprise the majority of the stratum corneum. The keratinocytes actually originate in the stratum basale, but as they mature and age, they move from the deepest to the most superficial layer of the epidermis.

Once the really old keratinocytes reach the stratum corneum, they are known as 'corneocytes.' The corneocytes are basically the cells that are shed off your skin and become part of the dust floating around you. Disgusting, isn't it? When you inhale dust, you also inhale dead human skin cells.

As yucky as that might sound, the keratinocytes do play a lot of important roles. One of these roles actually involves the melanin produced by melanocytes. The keratinocytes take up and store some of the melanin produced by the melanocytes, and this gives your skin an extra layer of protection from the damaging ultraviolet radiation of the sun's light rays.

Keratinocytes store melanin, giving skin an extra layer of protection from UV rays.
Keratinocytes Store Melanin

In addition to housing young keratinocytes and melanocytes, the basal layer of your skin also contains other cells, such as Merkel cells, which are cells that are important in the sensation of touch.

With all of that in mind, I do have an important point to make. The topmost layer of your skin we are going over, the epidermis, is made up of something called 'squamous' cells, which are basically a bunch of really flat cells. Bearing those squamous cells in mind, the 'basal' layer of the epidermis where the 'Merkel' cells and 'melanocytes' are located, it should come as absolutely no shocker that:

  • Squamous cell carcinoma
  • Basal cell carcinoma
  • Merkel cell carcinoma
  • Melanoma

are just some of the types of skin cancer you can get due to overexposure to damaging ultraviolet radiation from the sun's light rays. The next time you're frying at the beach, remember, your tan may be pretty, but skin cancer looks really nasty.

The Dermis

Furthermore, in serious cases of sunburn, even the next layer of skin, the layer right underneath the epidermis, can be affected. This layer of skin is called the dermis, and it is the middle layer of the skin, right below the epidermis.

The dermis and epidermis are separated by the basement membrane.
Basement Membrane Separates Dermis and Epidermis

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