01.06 Skin Structure & Function

Okay guys, in this lesson, we’re going to look at the structure of the skin and its functions.

So, first, let’s look at the different layers of the skin. There are three MAIN layers that we’ll see - the Epidermis, which is the outermost layer. This is a layer of keratinized stratified squamous epithelium. Remember that keratin helps waterproof our skin! Next is a layer of connective tissue called the Dermis. This is where we find our blood vessels, nerve endings, hair follicles, and our oil and sweat glands. You’ll notice the difference here between thick skin and thin skin. Thick skin tends to not have the hair follicles or oil glands, while the thin skin does. Thick skin would be like on the bottom of your feet or the palms of your hands - thin skin is… well… everywhere else! Underneath the dermis is a layer called the subcutaneous layer or subcutaneous tissue. Now… technically this is not actually a part of the skin - but it’s what the skin is connected to and plays a huge role in the benefits of skin. It is made of areolar connective tissue and adipose tissue and it connects our skin to the structures underneath it - whether that’s muscle, cartilage, or bone.

Now, the skin has a lot of really cool functions, so let’s touch on each of them. First is protection - our skin is LITERALLY our barrier against the outside world, right? So it protects our insides from injury, helps keep out infection, and protects us from UV radiation (we hope). We also see skin protecting us in terms of our fluid balance. Not only does it help hold our fluids IN so we don’t get too dehydrated, but it also helps keep water OUT. Remember that keratin we talked about? Over time, with too much water exposure, the skin can start to prune up because we are losing the keratin - that’s a sign that it’s time to get out of the water! Once we dry out, the keratin is restored and we’re protected once again!

Skin also plays a huge role in sensory detection - there are specialized neurons, or nerve endings, in the dermis that help us to detect light touch, deep pressure, temperature, and pain. Without that, it’s really difficult to get our bearings or prevent injury.

Another main function of skin is thermoregulation - so there’s 3 main ways our bodies lose heat. One is by radiation - that’s when the heat gets transferred without having to be in contact. So think about your radiator at home or a fire place - that’s heat transfer by radiation. You’re not actually touching it, but you’re getting heat from it. There’s also evaporation - when water gets hot, it vaporizes and takes the heat with it, so the surface is left cooler than it was. And last is conduction - this is when the heat transfers through contact. So if you touch a hot stove or use an ice pack - we’re using the principle of conduction to regulate temperature.

So let’s see what this looks like in the body. Let’s say we need to LOSE some heat - our temperature is too hot. Remember our bodies want to be at about 98.6 fahrenheit or 37 degrees celsius. So if we’re too hot, our blood vessels in the skin are goign to vasodilate - that means they get bigger and we get MORE blood flow to the skin. That blood is hot - so we end up losing some of that heat by radiation off the skin. Think about when you’re hot - you get really flushed and your skin gets hot - so you can get rid of some of your heat that way. We’ll also start sweating so we can lose some heat by evaporation. The whole goal is to get back to a normal temperature.

So what if we need to GAIN some hat - our temp is too cold. Well we’ll do just the opposite - the vessels constrict to keep whatever warm blood we have inside the body so we have LESS heat loss at the skin. We also see shivering because muscle contraction is a great way to product more heat. And of course there are other hormonal activities going on in the body to help us increase our temp.

A few other miscellaneous functions of skin - the skin is responsible for vitamin D production - when we take in sunlight through our skin, it tells the liver to convert cholesterol to vitamin D. We also see excretion of wastes in the form of urea in our sweat. And we also see identification through the skin with things like fingerprints and birthmarks.

So let’s recap - the skin has 3 layers - the epidermis, dermis, and subcutaneous tissue. The primary functions of skin are protection, sensory detection, and thermoregulation, plus a couple miscellaneous ones. We see radiation, evaporation, and conduction as ways to transfer heat and the skin plays a role in that - especially through radiation with vasodilation and constriction, sweating, and shivering.

Okay guys, those are the basics you need to know about skin. Now, go out and be your best self today. And, as always, happy nursing!!