Skin: Layers, Structure and Function

Your skin is incredible. Whether you’re a bright young thing without a wrinkle in sight, someone who’s struggled with acne their entire lives, or an older person in the first flushes of menopause wondering what the hell’s going on with your complexion, your skin is still a miracle of nature. It’s hard at work every day underneath all the grease, sweat, dirt, pollution, makeup, and gunk.

What is the skin?

Human skin is the largest and heaviest organ of the body, and has three major layers that also have layers within them. The skin is important to life as it is a barrier to the outside world; with broken or ineffective skin the body would be susceptible to infection and the adverse effects of the sun’s radiation (cancer). The most important functions of the skin are protection, sensation, thermoregulation and vitamin D synthesis.

What does skin do?

Your skin is a living, breathing mechanism working overtime. Below are just a few of the jobs it’s doing, 24 hours a day:

  • Acting as a waterproof shield so that vital nutrients don’t leak out of your body (gross).
  • Regulating your temperature, by opening and closing blood vessels, and perspiring to allow sweat to evaporate and cool us down.
  • Acting as a barrier between your insides and the many harmful toxins and microorganisms in the environment.
  • Sweating out waste products including salt and ammonia.
  • Helping protect you from sun damage by producing melanin.
  • Synthesising vitamin D for strong bones and healthy organs.
  • Patching itself up against the various cuts, bruises, grazes and burns that we get day to day.
  • Giving us that little thing known as the sense of touch, which we’d be pretty screwed without.

It’s complex, and it deserves respect. To understand how your skincare products work, it can help to have a basic understanding of what goes on beneath your skin.

What are the layers of the skin?

The skin consists of three layers:

  • Epidermis, the top layer.
  • Dermis, the middle layer.
  • Hypodermis, the bottom or fatty layer.

What does the epidermis (top layer of skin) do? 

This is the outermost part of the skin, and the bit that you see. It’s made up of keratinocytes (our skin cells), and is the part of you that keeps bacteria at bay. It’s your first line of defence.

Your epidermis is constantly renewing and regenerating, with new cells made in the lowest layer, the basal cells, and travelling, over the course of about a month, to the top. The ‘living’ layers of cells are known as the ‘squamous cells’, which eventually become a layer of dead keratinocytes that are constantly shedding in the stratum corneum. This process slows down as you get older. So, making sure you’re keeping your skin clean and exfoliated is important if you don’t want your complexion to look dull and lifeless.

The bottom layer of the epidermis also produces melanin, which helps protect you from UV rays and gives your skin its colour. When you tan, your skin is actually producing more melanin in an attempt to shield you from the sun.

Over-the-counter skincare will only ever treat the epidermis. If you want to go deeper, you’ll need a prescription or a needle.

What does the dermis (middle layer of skin) do?

This thicker layer of your skin contains the blood vessels and nerves that give you your sense of touch. The connective tissues are made up of two proteins: collagen, which gives skin its fullness and shape; and elastin, which gives skin its resilience and its ability to ‘snap’ back into shape. The cells that make these proteins are bathed in hyaluronic acid, a cellular lipid that holds water and gives your skin its bounce and texture.

When you are young, the dermis is so full of collagen and elastin that it can bounce back into shape, but as we age, they break down faster than our cells can replace them, and this leads to wrinkles and dry skin.

The dermis also contains your hair follicles and oil glands, as well as the beginning of your pores, which push hair, sweat and oil to the surface.

What does the hypodermis (bottom layer of skin) do?

The Hypodermis layer or Subcutaneous layer, is the third major layer. The primary function of the hypodermis layer is to act as a fat storage which has great benefits in the way of insulation, but mainly fat is the body’s store of reserve energy. Being deeper the hypoderm has larger blood vessels, and so cuts that penetrate to this region may cause severe bleeding.

The subcutaneous tissue layer tends to thin as we age, and when this happens our skin looks less smooth, and the underlying veins show through. It also results in cellulite in other areas of the body.

Nobody’s asking you to go back to biology class, but if you understand the basics of how your skin works, you can start to understand the claims that the skincare industry is making, what works, and what’s totally impossible, what it does for you, and what you can do for it.

What conditions and disorders affect the skin?

There is a wide range of severity and symptoms associated with skin disorders. There may be painless or painful symptoms, and they may be temporary or permanent. Other causes may be genetic, while others may be situational. Skin conditions can range from minor to life-threatening. These include:

  • Skin allergies, such as poison ivy rashes and contact dermatitis.
  • Blisters.
  • Skin infections
  • Skin rashes and dry skin.
  • Skin disorders like acne, psoriasis, eczema and vitiligo.
  • Skin lesions, such as freckles, moles and skin tags.
  • Skin cancer
  • Bites from insects, such as spiders, ticks, and mosquitoes.
  • Scars, burns (including sunburns), and wounds.

How can I protect my skin?

It is not enough to know your skin type: You also need to understand its primary needs. In the following sections, we’ll give you the details so you can build a skincare routine that works for you.

Cleanse your skin every night without fail – cleanliness is next to Godliness. Double cleanse if you are wearing makeup or sunscreen, or both (which applies to most of us).

A little tip for those of you that say you have no time: either take your makeup off as soon as you get home OR take your makeup off before you take your bra off (if you sleep in your bra or don’t wear one, then follow the first tip!).

Cleanse your skin every morning. It obviously doesn’t have to be as intense as the nighttime cleanse, but a quick warm flannel and milk/balm/gel wouldn’t go amiss to get rid of the overnight shedding. I know some brands say you don’t need to cleanse your skin in the morning. That’s okay. They’re wrong.

Wash your face properly. A clean canvas makes everything better. There is no point in spending your hard-earned cash on expensive serums if you are using wipes or winging it when it comes to cleansing. See here for more on cleansing.

Do not smoke. That’s really the beginning and end of it.

Get some sunshine. The term ‘everything in moderation’ really applies here. I work indoors all day and live in the northern hemisphere. I don’t get a lot of suns so I supplement with vitamin D (under doctor’s advice). I don’t use skincare with SPF: I apply it separately in between moisturizer and foundation or primer. SPF is too active an ingredient and can interfere with other anti-aging ingredients, making all of your expensive moisturizers potentially redundant.

Yes, obviously too much sun is damaging to the skin, but so is too much chlorine. And too much pollution. Get out there and get some sunshine. Some brands would have us believe the sun is the ultimate enemy. That’s only true if you don’t respect it. Get some sun. Not a lot, some. Just don’t be stupid about it.

Use a high SPF (30+) and encourage your kids to use it. You will save them a lot of time trying to repair sun damage in later years.

Use good-quality skincare. I’m not talking about creams that cost more than your monthly food budget; I’m just suggesting you step away from the cheap packet of wipes and moisturizers in the chemist or supermarket and step it up a gear.

Equate your skincare spending to what you would spend on a handbag or shoes. I’m not saying you should – I’m saying you should be willing to. 

Get enough sleep. When you are not getting sufficient rest, it shows on your face.

Try to eat well. I’m not being a killjoy – a little of what you fancy definitely do you good – just don’t go overboard. Gut health is linked to healthy skin function: for example, taking probiotics is thought to support healthy skin.

Drink enough water. This is important not only for the normal functionality of your skin but for your general good health, too. If your urine is dark and you suffer from a lot of headaches, you would do well to up your H2O levels.

Try to avoid stress. I know it’s much harder than it sounds, but do whatever you need to do to keep your stress levels low.

When should I talk to a doctor?

You should call your healthcare provider if you experience:

  • A mole or patch of skin that’s changed— If the color, size, shape, or symptom of a mole or patch of your skin has changed, you should consult a dermatologist. Such changes are frequently signs of skin cancer, and when it comes to cancer, you want treatment as soon as possible.
  • Stubborn acne—You’ve tried over-the-counter products, fad diets, and cleanses, but your acne persists.
  • Itchy hives or rashes that won’t go away
  • Scars from acne, blemishes, or cuts and scrapes— If your scar is unsightly, a dermatologist may be able to help. Scarring can be reduced using medical techniques such as laser treatment therapy, microdermabrasion, and others.
  • Persistent skin irritation—You have itchy, red, flaky skin that isn’t responding to over-the-counter creams and lotions. You may believe that your dry skin is caused by the weather, sensitivity to skincare products, or even genetics. However, you could have a chronic skin condition.

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