Functions of the Skin

Human skin performs many responsibilities and functions. The first and most obvious is protection. Without the skin and its keratin, pathogens could easily reach important parts of the body. Sweat contains lysozyme, an antimicrobial enzyme that attacks bacteria. The sensory receptors in the dermis provide the ability to feel touch, pain, and temperature. The dermis also contains more blood than the skin actually uses, which allows the skin to regulate the body’s temperature. The skin’s keratin helps create a barrier that prevents fluids from washing essential nutrients out of the body.

Colour of the Skin

Colour

Melanin is a pigment the epidermis produces to protect the skin from the sun’s rays. The more melanin a person has, the darker their skin tends to be. This is why ethnicities that developed in tropical regions typically have darker skin tones. Without melanin, various colors are more visible through the skin. Underneath the dermis is bluish-white connective tissue, which is why some individuals appear to have "white" skin. This is also why exercise or certain emotions may make some people red and others not: arterioles dilate and allow more blood flow during these events. Some individuals may appear to have a more yellow, purple, or red coloring to their skin. Carotene is a yellow or orange pigment in the dermis. Hemoglobin is a purple color in the blood, and oxyhemoglobin is a red color in the blood.

Sebaceous Gland

Oil

Within the dermis are the sebaceous glands or oil glands. The palms of the hands and the soles of the feet are the only areas of the body that do not contain sebaceous glands. These glands produce sebum, an oily fluid that lubricates the skin. Sebum also breaks sweat into many fine droplets to prevent dehydration. If the glands malfunction or are overactive, they can produce too much sebum. Oily skin is not necessarily a negative, as oily skin is less prone to signs of aging, such as wrinkles. However, the oil can lead to pores becoming clogged and dead skin cells accumulating on the skin’s surface.

Ageing

Keratinization constantly providing new cells for the skin does not prevent the skin from aging. Typically, skin is fairly soft and smooth. Once a person reaches the age of 20, their body produces one percent less collagen every year. This is why the skin becomes thinner. The body also produces less elastin, the protein responsible for the skin's elasticity. Experts refer to this as intrinsic aging and it would typically cause only minor wrinkles. Smoking, being in the sun, gravity, pollution, and even making facial expressions are examples are extrinsic aging. Intrinsic and extrinsic aging pair together to create the defined wrinkles and other features we associate with aged skin.

Skin can warm and cool you

Skin Can Warm and Cool You

Your skin can help if you're feeling too hot or too cold. Your blood vessels, hair, and sweat glands cooperate to keep your body at just the right temperature. If you were to run around in the heat, you could get overheated. If you play outside when it's cold, your inner temperature could drop. Either way, your skin can help.
Your body is pretty smart. It knows how to keep your temperature right around 98.6°F (37°C) to keep you and your cells healthy. Your skin can respond to messages sent out by your hypothalamus (say: hy-po-THAL-uh-mus), the brain's inner thermometer.
If you've been running around on a hot day, your blood vessels get the signal from the hypothalamus to release some of your body's heat. They do this by bringing warm blood closer to the surface of your skin. That's why you sometimes get a red face when you run around.
To cool you down, sweat glands also swing into action by making lots of sweat to release body heat into the air. The hotter you are, the more sweat your glands make! Once the sweat hits the air, it evaporates (this means that it changes from a liquid to a vapor) off your skin, and you cool down.
What about when you're ice-skating or sledding? When you're cold, your blood vessels keep your body from losing heat by narrowing as much as possible and keeping the warm blood away from the skin's surface. You might notice tiny bumps on your skin. Most kids call these goosebumps, but the fancy name for them is the pilomotor (say: PY-lo-mo-ter) reflex. The reflex makes special tiny muscles called the erector pili (say: ee-REK-tur pee-LEE) muscles pull on your hairs so they stand up very straight.

Skin Conditions

Rash: Nearly any change in the skin’s appearance can be called a rash. Most rashes are from simple skin irritation; others result from medical conditions.
Dermatitis: A general term for inflammation of the skin. Atopic dermatitis (a type of eczema) is the most common form.
Eczema: Skin inflammation (dermatitis) causing an itchy rash. Most often, it’s due to an overactive immune system.
Psoriasis: An autoimmune condition that can cause a variety of skin rashes. Silver, scaly plaques on the skin are the most common form.
Dandruff: A scaly condition of the scalp may be caused by seborrheic dermatitis, psoriasis, or eczema.
Acne: The most common skin condition, acne affects over 85% of people at some time in life.
Cellulitis: Inflammation of the dermis and subcutaneous tissues, usually due to an infection. A red, warm, often painful skin rash generally results.
Skin abscess (boil or furuncle): A localized skin infection creates a collection of pus under the skin. Some abscesses must be opened and drained by a doctor in order to be cured.
Rosacea: A chronic skin condition causing a red rash on the face. Rosacea may look like acne, and is poorly understood.
Warts: A virus infects the skin and causes the skin to grow excessively, creating a wart. Warts may be treated at home with chemicals, duct tape, or freezing, or removed by a physician.
Melanoma: The most dangerous type of skin cancer, melanoma results from sun damage and other causes. A skin biopsy can identify melanoma.
Basal cell carcinoma: The most common type of skin cancer. Basal cell carcinoma is less dangerous than melanoma because it grows and spreads more slowly.
Seborrheic keratosis: A benign, often itchy growth that appears like a “stuck-on” wart. Seborrheic keratoses may be removed by a physician, if bothersome.
Actinic keratosis: A crusty or scaly bump that forms on sun-exposed skin. Actinic keratoses can sometimes progress to cancer.
Squamous cell carcinoma: A common form of skin cancer, squamous cell carcinoma may begin as an ulcer that won’t heal, or an abnormal growth. It usually develops in sun-exposed areas.
Herpes: The herpes viruses HSV-1 and HSV-2 can cause periodic blisters or skin irritation around the lips or the genitals.
Hives: Raised, red, itchy patches on the skin that arise suddenly. Hives usually result from an allergic reaction.
Tinea versicolor: A benign fungal skin infection creates pale areas of low pigmentation on the skin.
Viral exantham: Many viral infections can cause a red rash affecting large areas of the skin. This is especially common in children.
Shingles (herpes zoster): Caused by the chickenpox virus, shingles is a painful rash on one side of the body. A new adult vaccine can prevent shingles in most people.
Scabies: Tiny mites that burrow into the skin cause scabies. An intensely itchy rash in the webs of fingers, wrists, elbows, and buttocks is typical of scabies.
Ringworm: A fungal skin infection (also called tinea). The characteristic rings it creates are not due to worms.

Skin Tests

Skin biopsy: A piece of skin is removed and examined under a microscope to identify a skin condition.
Skin testing (allergy testing): Extracts of common substances (such as pollen) are applied to the skin, and any allergic reactions are observed.
Tuberculosis skin test (purified protein derivative or PPD): Proteins from the tuberculosis (TB) bacteria are injected under the skin. In someone who’s had TB, the skin becomes firm.

Skin Treatments

Corticosteroids (steroids): Medicines that reduce immune system activity may improve dermatitis. Topical steroids are most often used.
Antibiotics: Medicines that can kill the bacteria causing cellulitis and other skin infections.
Antiviral drugs: Medicines can suppress the activity of the herpes virus, reducing symptoms.
Antifungal drugs: Topical creams can cure most fungal skin infections. Occasionally, oral medicines may be needed.
Antihistamines: Oral or topical medicines can block histamine, a substance that causes itching.
Skin surgery: Most skin cancers must be removed by surgery.
Immune modulators: Various drugs can modify the activity of the immune system, improving psoriasis or other forms of dermatitis.
Skin moisturizers (emollients): Dry skin is more likely to become irritated and itchy. Moisturizers can reduce symptoms of many skin conditions.

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