Skin is a miracle garment. It's soft, pliable, strong, waterproof, and self-repairing. The unfortunate thing is that in our society today, there is a lot of emphasis placed on physical appearance and the interior potential of people is conveniently overlooked. Skin is considered as a major sex organ as its feel is sensually vital. Your personal appeal begins with your view of yourself, the pleasure and joy you take in being who you are. Take a fresh, new look at yourself right now. Get to know and appreciate that special person. Without skin, people's Muscles, bones, and organs would be hanging out all over the place. Our skin holds everything together. It also:

Protects our bodies. Helps keep our bodies at just the right temperature. Allows us to have the sense of touch.

Our body's largest organ makes up about 15% of our total weight and covers 20 square feet. Paper-thin and incredibly complex, your skin protects you from the perils of your environment and allows you to feel pain and pleasure. It's working to renew itself every second of every day. So how well do you really know the back of your hand - or for that matter, any square inch of your skin?

In what single place can you find the following things: 19 million cells, 625 sweat glands, 90 oil glands, 65 hairs, 19 feet of Blood vessels, and 19,000 sensory cells? The answer: in one square inch of human skin! Your skin, or integument, has many different protective and metabolic functions that help keep your body stabilized. The skin is made up of three layers, each with its own important parts. 1) Outer layer is called the epidermis. 2) Dermis. 3) Subcutaneous fat. The old saying, "beauty is skin deep", carries with it a certain amount of truth. Our skin is the part of us we show to the world. Its appearance reflects our age, origin, health, and even state of mind. It has an unbelievable ability to repair itself - but it's not invincible. One out of three people will experience some kind of skin problem during their lifetime.

The skin is a metabolically active organ with vital functions such as protection and homeostasis. When discussing the physiology of the skin and its derivatives, the following topics are to be considered:

Keratinocyte Maturation, Melanocyte Function, Hair Growth, and Temperature Regulation.

Keratinocyte Maturation

The aging of basal cells into the corneocytes (dead cells) is crucial. The stratum corneum is important in preventing all manner of agents from entering the skin, including microorganisms, water and particulate matter. It is the epidermis that also prevents loss of vital body fluids. The dividing basal Cell on average replicates every 200 to 400 hours, and the resulting Cell takes 14 days to differentiate and 14 days to be shed. Keratinocyte maturation can be divided into five sequences: 1) In the basal layer (stratum basale), undifferentiated cells and cells in the layer immediately above divide continuously. Half of these cells progress upwards and differentiate, while the other half remain behind to divide again. 2) In the prickle Cell layer (stratum spinosum), the shape of cells change from columnar to polygonal. Differentiating keratinocytes synthesize keratins, which aggregate to form tono-filaments. Condensations of these tono-filaments form desmosomes, which connect keratinocytes. Desmosomes maintain a distance of 20 nanometers between adjacent cells and distribute structural stresses throughout the epidermis. 3) In the granular layer (stratum granulosum), enzymes induce degradation of nuclei and organelles. Keratohyalin granules mature the keratin and provide an amorphous protein matrix for the tono-filaments. Membrane coating granules attach to the Cell membrane and release an impervious lipid containing cement which contributes to Cell adhesion and to the horny layer barrier. 4) In the horny layer (stratum corneum), the dead flattened corneocytes have developed thickened Cell envelopes enclosing a matrix of keratin tono-fibrils. The disulphide bonds of keratin provide the strength to the layer, but the horny layer is also flexible and can absorb up to three times its weight in water. However, if the layer dries out (below 10% water content), pliability fails. 5) Corneocytes are shed from the skin surface.

Melanocyte Function

Melanocytes are located in the basal layer. In this location, they produce the pigment melanin in elongated, membrane-bound organelles known as melanosomes. Melanin is packaged into granules, which are moved down dendritic processes and transferred by phagocytosis to adjacent keratinocytes. In the inner layers of the epidermis, melanin granules form a protective cap over the outer part of keratinocyte nuclei. In the stratum corneum, melanin granules are uniformly distributed to form a UV-absorbing blanket, which reduces the amount of radiation penetrating the skin. UV radiation - mainly the wavelengths of 290 to 320 nm (UVB) - darkens the skin firstly by immediate photo-oxidation of preformed melanin, and secondly over a period of days by stimulating melanocytes to produce more melanin. UV radiation also thickens the epidermis by inducing keratinocyte proliferation. Contrary to popular belief, variations in racial pigmentation are not due to differences in melanocyte numbers, but to the number and size of melanosomes produced. Red-haired people have the pigment phaeomelanin and their melanosomes are spherical, rather than the more common eumelanin pigment and oblong melanosomes.

Hair Growth

Unlike most mammals, humans are considered "nude"; thus, our Hair does not play the same vital role of heat conservation. However, the Hair on our scalp does protect us from UV radiation and minor injury. More importantly today, our Hair is of cosmetic value. Hair growth is cyclical and has three phases. Hair growth is generally randomized for individual hairs, but can become synchronized during pregnancy. The three phases are: 1) Anagen is the growing phase. The duration of this phase depends on the location of the Hair. For eyebrow Hair, this phase only lasts 4 months, but for scalp Hair it lasts from 3-7 years. At any moment, 80-90% of scalp hairs are in anagen; daily, approximately 50-100 scalp follicles switch to the catagen phase. 2) Catagen is the resting phase and lasts 3-4 weeks. There is a stop to Hair protein synthesis as the Hair follicle retreats towards the surface. At any moment, less than 1% of hairs are in the catagen phase. 3) Telogen is the shedding phase and is characterized by hairs with a short club Root. Daily, approximately 50-100 scalp hairs are shed. At any moment, 10-20% of scalp hairs are in telogen.

Temperature Regulation

The homeostasis of our body temperature at 37°C is vital to many biochemical reactions. Temperature regulation depends on metabolism and exercise, but the skin plays a crucial role in controlling temperature through the direct heat loss from its surface and by the evaporation of sweat. 1. Blood Flow: Skin temperature is highly dependent on skin Blood flow. Contraction or dilation of the dermal Blood vessels results in vast changes in Blood flow. Under the control of the sympathetic Nervous system ("flight or fright"), arteriovenous anastamoses shunts Blood to the superficial venous plexus to cause heat loss by convection and radiation. 2. Sweat: Sweat cools the skin by evaporation. The minimum daily insensible perspiration is 0.5 liters. Maximum daily secretion is 10 liters, with a maximum output of 2 liters/hour. Factually, men sweat more than women. Initially, the sweat gland produces an isotonic sweat, which is then modified in the excretory portion of the duct. Only small amounts of toxic substances are lost via sweat. Sweating may also occur in response to emotion or after eating spicy food. In addition, besides being involved in thermoregulation, sweat also maintains hydration of the stratum corneum and improves the grip on our palms and soles.

Skin has many functions, and is far more than a mere decoration for the body. Some of these functions are so important that unless most of the skin is working efficiently, we will die. Although we think of the skin as a single organ, the epidermis and dermis have to some extent separate functions. The function of water conservation is however dependent on both; the role of the stratum corneum in this field is absolutely vital, as it acts as a semi-permeable barrier and allows us to survive in a hostile environment. The epidermis has three principal functions:

Protecting the body from the environment, particularly the sun, Preventing excessive water loss from the body, and Protecting the body from infection.

Functions of the dermis:

Giving mechanical protection to the body from bumps and knocks; the collagen has an important role in this function. Providing oxygen and nutrients, via Blood in the tiny vessels that run in the ground substance, to the living part of the epidermis. Removing waste products of metabolism from the epidermis, which are also carried away in the Blood. Providing shape and form to the body, by holding all its structures together. Contributing to skin color, particularly in people with little melanin in the epidermis.

Organs in the dermis have special functions of their own:

Regulation of body temperature, through the control of Blood flow and sweating. Skin sensations of touch, pain, heat and Cold. It gathers sensory information from the environment, and plays an active role in the immune system protecting us from disease.

Thus skin plays a very important role in the human body, from adding beauty to protection.

Abscess Acne Acne Rosacea Albinism Allergy Bed Sore Bites and Stings Boils(Furunculosis) Burns Chicken Pox Cholasma Cold Sore Dermitis Dermoid Cyst. Diaper Rash Eczema Erysipelas Freckles Frost Bites German Measles Head Lice Herpes Zoster Impetigo Keloid Lichen Planus Lipoma Measles Melanoma Melasma Molluscum Contagiosum Nail Diseases Paronychia Pemphigus Photosensitive Disorder Pigmentation Disorder Pityriasis Psoriasis Scabies Tinea Versicolour Urticaria Vitiligo Warts