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.
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
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.
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.
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
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.
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 is separated from the epidermis by something called the ‘basement membrane,’ which is basically a thin sheet of tissue that anchors down the epidermis to the deeper levels of the skin, and also helps to prevent the passage of certain cells and molecules between the two layers.Furthermore, the dermis contains glands, nerves, blood vessels, and hair follicles.
In addition, the dermis has a famous protein called collagen, which gives our skin its strength and some elasticity. With age, a poor diet, or sun exposure, the collagen will break down, and this will lead to the sagging and wrinkling of our skin.
The deepest layer of skin, is the subcutis, or subcutaneous layer. It is located right below the dermis. It is also sometimes called the ‘hypodermis.’ Note that the words ‘subcutaneous’ or ‘hypodermis’ translate as ‘under the skin.’ So, when you get a ‘subcutaneous’ injection with a ‘hypodermic’ needle, the needle goes below the epidermis and dermis and into this level.
In addition to blood vessels and nerves, the subcutis layer of the skin is made up of adipose tissue, also known as body fat, and other types of connective tissue as well.
Well, if you ever need something to distract you from the thought of cancer and wrinkle inducing death rays the sun provides you with free of charge, try reviewing the important points of this lesson with me.The epidermis is the outermost layer of the skin. The dermis is the middle layer of the skin, and the subcutis is the innermost layer of the skin. In the epidermis, there are cells that eventually die in order to comprise the majority of the stratum corneum. These cells are called keratinocytes.Also, within the basal layer of the epidermis, there are cells called melanocytes.
These are cells that produce the pigment melanin. Finally, the basal layer of the epidermis also contains cells called Merkel cells, which are cells that are important in the sensation of touch.
After watching this video, you’ll be able to:
- List the three main layers of the skin
- Identify the layers of the epidermis from outermost to innermost
- Explain the different types of skin cells in the epidermis and their functions
- Name four types of skin cancer