Human Skin Content from the guide to life, the universe and everything

Human Skin

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Faculty of Medical, Clinical and Veterinary Sciences


Skin Problems

Human Skin | Dry Skin | Psoriasis | Eczema | Greasy Skin | Dandruff | Acne | Rosacea | Seborrheic Dermatitis | Skin Cancer | Non-melanoma Skin Cancer | Melanoma | Hereditary Skin Cancer | Sensible sun exposure

The skin - or to use the correct term, cutaneous membrane - is the largest organ in the human body. There are about two square metres of it covering an average adult and it accounts for about an eighth of the total body weight. It's the body's first line of defence against a hostile environment, being waterproof (from both directions) and germ-proof. It also acts as a temperature control mechanism and the main access to one of the senses - touch.

There are two distinct parts of the skin, known as epidermis and the dermis and a third layer, the hypodermis or subcutaneous tissue, not strictly skin, but made up of fatty cells which lie below the skin.

The bit we can see and touch is the epidermis. Most of the epidermis is made up of dead skin cells - the living cells at the bottom of the epidermis rise to the surface of the skin, hardening, flattening, and eventually being shed providing us with the outermost layer of protection. Interestingly, dead skin cells constitute over 90% of house dust.

The lower, living levels of the epidermis also contain melanin - the pigment that gives skin its colour and protects it from the sun - and a chemical compound called ergosterol that produces vitamin D in sunlight.

The bottom layer of skin, the dermis, is richly supplied with blood vessels; this is the part of skin in which hair follicles, sweat and sebaceous glands, and nerve endings are located. The nerve endings are in ridges that push into the epidermis in a slightly different pattern in everybody. This is the reason behind unique fingerprints.

There are two different types of sweat gland. The first, the eccrine glands, produce a salty liquid and these are located all over the skins surface. This is used as a temperature control mechanism, but the liquid is also slightly acidic, which is useful for keeping down bacteria that live naturally on the skin.

The other type - the apocrine glands - are the ones responsible for body odour. These glands are only located in the armpits and genitals and secrete a mixture of protein and fat. The bacteria that live on the skins surface thrive on this and cause body odour. The apocrine glands only start to become active at puberty.

The other type of gland found in the dermis are the sebaceous glands. These secrete an oily substance that keeps the epidermis waterproof and the hair supple.

Problems, Problems

There are two basic reasons for things that go wrong with the skin - environmental and genetic predisposition. For instance:

  • The immune system has to be very active within the skin; it is the body's first line of defence against germs. Sometimes the body will react to a threat that isn't there, or overreact to one that is. These types of reaction could lead to eczema or psoriasis.

  • The sebaceous glands can clog up and become infected, bringing on an outbreak of acne.

  • Central heating and excess cleansing can lead to dry skin. Conversely, a humid climate, hormones and over cleansing can give rise to excessively greasy skin.

  • Everybody blushes occasionally, but in some the tiny blood vessels in the skin stay swollen and dilated, a condition called rosacia.

  • If the outer layer of skin cells aren't being shed normally, the build up can be seen with dandruff or psoriasis.

  • Being constantly exposed to everything the environment can throw at it, including carcinogens, the skin can be susceptible to skin cancers.

  • Of course, the skin is also vulnerable to attacks from other organisms, like a virus causing cold sores or warts, or fungus which causes athletes foot.

There are also a lot of misconceptions and Old Wives Tales about the causes and cures of some skin problems. Luckily, most are now laughed at, but it wasn't so long ago that people thought that:

  • Eating chocolate and chips caused greasy skin.

  • Masturbating caused acne.

  • Going back a little further, someone with eczema or psoriasis could expect to spend their life in a leper colony!

Although we do have a much greater understanding of these problems now, some people with skin problems do still feel stigmatised, simply due to the high visibility of their condition. It would be unfair to say this stems purely from vanity; much is fear of other people's reactions.

The psychological effects of a skin condition on the sufferer can be grossly disproportionate to the amount of physical harm their condition causes. This can be especially problematical for children, when teasing can be a problem, and for teenagers, at a very sensitive time in their physical development. However, it is not confined to simply these age groups - adults can suffer from psychological disorders and all age groups can suffer if they're constantly loosing sleep because of constant itching.

The skin can also be quite a reliable meter for gauging general health - it can be quite obvious when someone is run down, tired or ill, just by looking at their skin. There is also the possibility that a skin problem could be the first symptom of another disease1, so it's always worth getting a medical opinion of something that gives any cause for concern - which can sometimes be a problem in its own right. People with skin problems are often unwilling to seek a doctor or dermatologist's help, or reluctant to return if the first treatment prescribed fails to help, thinking that there's nothing that can be done, but often this couldn't be further from the truth.

Find a sympathetic doctor and remember, there are lots of both OTC2 and prescription-only formulations available - it's worth persisting.

1For instance, both diabetes and kidney disease can cause itching.2Over-the-counter, treatments available without a prescription.

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