Your skin is your biggest organ. If the skin of a common 150-pound (68-kilogram) adult male were stretched out flat, it would certainly cover about 2 square yards (1.7 square meters) and weigh about 9 pounds (4 kilograms).

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Skin protects the network of muscles, bones, nerves, blood vessels, and everything else inside our bodies. Eyelids have the thinnest skin, the soles of our feet the thickest.

Hair is actually a modified kind of skin. Hair grows almost everywhere on the person body other than the palms the the hands, soles that the feet, and also lips. Hair grows an ext quickly in summer 보다 winter, and an ext slowly in ~ night than during the day.

Like hair, nails space a type of amendment skin — and also they’re not simply for beauty. Nails safeguard the sensitive tips of ours fingers and toes. Human nails room not vital for living, but they do provide support because that the advice of the fingers and also toes, safeguard them indigenous injury, and assist in choose up tiny objects. Without them, we’d have a difficult time scratching one itch or untying a knot. Nails deserve to be an indicator that a person’s basic health, and also illness regularly affects their growth.

Skin Basics


Skin is necessary to a person’s survival. It creates a barrier that prevents harmful substances and also microorganisms native entering the body. The protects body tissues versus injury. Our skin also controls the loss of life-sustaining fluids prefer blood and water, helps us regulate body temperature through perspiration, and also protects united state from the sun’s damaging ultraviolet rays.

Without the nerve cells in our skin, we couldn’t feel warmth, cold, or various other sensations. Ours skin can additionally respond come situations and emotions: muscle in the skin called erector pili contract to do the hairs on our skin stand up right (goosebumps) when we space cold or fearful — because that insulation and protection.

Every square customs of skin has thousands that cells and hundreds of sweat glands, oil glands, nerve endings, and also blood vessels. Skin is consisted of of three layers: the epidermis (pronounced: ep-ih-dur-mis), dermis, and the subcutaneous (pronounced: sub-kyoo-tay-nee-us) tissue.

Skin Cells and also Layers

The top layer of our skin, the epidermis, is the tough, protective outer layer. That is about as thick together a paper of record over many parts that the body. The epidermis has four layers of cells that are constantly molting off and being renewed. In these four layers space three special types of cells:

Melanocytes (pronounced: meh-lah-nuh-sites) produce melanin, the pigment that offers skin its color. All human being have roughly the same variety of melanocytes; the an ext melanin that is produced, the darker the skin. Exposure come sunlight increases the production of melanin, i beg your pardon is why world get suntanned or freckled.Keratinocytes (pronounced: ker-uh-tih-no-sites) create keratin, a type of protein the is a straightforward component of hair and also nails. Keratin is also found in skin cells in the skin’s external layer, wherein it helps produce a security barrier.Langerhans (pronounced: lahng-ur-hanz) cells aid protect the body versus infection.

Because the cell in the epidermis are totally replaced around every 28 days, cuts and also scrapes heal quickly.

Below the epidermis is the following layer of our skin, the dermis, which is comprised of blood vessels, nerve endings, and also connective tissue. The dermis nourishes the epidermis.

Without details molecules in the dermis, ours skin wouldn’t stretch as soon as we bend or reposition itself as soon as we straighten up. This two species of fibers in the dermis, collagen and elastin, aid the skin stretch and reposition itself when we move. Collagen is solid and difficult to stretch and also elastin, together its surname suggests, is elastic. In enlarge people, some of the elastin-containing yarn degenerate, i beg your pardon is one reason why the skin looks wrinkled (most wrinkles are led to by sunlight exposure, though!).

The dermis additionally contains a person’s sebaceous glands. These glands, i beg your pardon surround and empty into our hair follicles and pores, develop an oil referred to as sebum (pronounced: see-bum) that lubricates the skin and also hair. Sebaceous glands are uncovered mostly in the skin top top the face, upper back, shoulders, and chest.

Most of the time, the sebaceous glands do the appropriate amount the sebum. As a person’s body begins to mature and develop during the teenage years, though, hormones stimulate the sebaceous glands come make more sebum. This can lead come acne once pores end up being clogged through too lot sebum and also too numerous dead skin cells. Later on in life, these glands develop less sebum, i m sorry contributes to dry skin in enlarge people.

The bottom layer of our skin, the subcutaneous tissue, is made up of connective tissue, sweat glands, blood vessels, and cells that store fat. This great helps safeguard the body from blows and other injuries and helps it host in body heat.

There are two types of sweat-producing glands. The eccrine (pronounced: eh-krun) glands are discovered everywhere in ours bodies, although lock are mostly in the forehead, palms, and soles of the feet. By creating sweat, these glands assist regulate body temperature, and waste assets are excreted v them.

The other type of sweat-producing gland, the apocrine glands, construct at puberty and also are concentrated in the armpits and pubic region. The sweat from the apocrine glands is thicker than that produced by the eccrine glands. Return this sweat doesn’t smell, as soon as it mixes v bacteria on the skin’s surface, that can reason body odor.

A normal, healthy adult secretes about 1 pint (about fifty percent a liter) of sweat daily, yet this may be raised by physical activity, fever, or a warm environment.

Hair Basics

The hair top top our heads isn’t simply there for looks. The keeps us heat by preserving heat. The hair in our nose, ears, and around our eyes protects this sensitive areas of the human body from dust and also other little particles. Eyebrows and also eyelashes defend our eyes by to decrease the amount of light and also particles that get in them. The good hair the covers ours bodies gives warmth and also protects ours skin. Hair also cushions the body versus injury.


Human hair consists of the hair shaft, which jobs from the skin’s surface, and also the root, a soft thickened bulb at the basic of the hair embedded in the skin. The root end in the hair bulb. The hair pear sits in a sac-like pit in the skin dubbed the follicle, from which the hair grows.

At the bottom that the follicle is the papilla, whereby hair growth actually take away place. The papilla includes an artery that nourishes the root of the hair. Together cells multiply and produce keratin to harden the structure, lock are propelled up the follicle and also through the skin’s surface ar as a tower of hair. Every hair has actually three layers: the medulla at the center, i beg your pardon is soft; the cortex, which surrounding the medulla and also is the main component of the hair; and the cuticle, the hard outer layer the protects the shaft.

Hair grow by forming new cells in ~ the basic of the root. These cells main point to kind a rod of organization in the skin. The rods of cells move upward v the skin as new cells kind beneath them. Together they move up, lock are cut off from their supply of nourishment and also start to kind a difficult protein called keratin in a procedure called keratinization (pronounced: ker-uh-tuh-nuh-zay-shun). As this process occurs, the hair cell die. The dead cells and keratin form the column of the hair.

Each hair grows about ¼ customs (about 6 millimeters) every month and also keeps on farming for up to 6 years. The hair then drops out and another grow in that place. The length of a person’s hair depends on the size of the cultivation phase that the follicle. Follicles are active for 2 to 6 years; they rest for about 3 months after that. A person becomes fully if the scalp follicles come to be inactive and no longer produce brand-new hair. Thick hair grows the end of huge follicles; small follicles create thin hair.

The shade of a person’s hair is established by the amount and also distribution the melanin in the cortex of each hair (the same melanin that’s discovered in the epidermis). Hair likewise contains a yellow-red pigment; civilization who have actually blonde or red hair have actually only a little amount the melanin in your hair. Hair becomes gray when people age because pigment no longer forms.

All about Nails

Nails grow out that deep folds in the skin that the fingers and also toes. As epidermal cells below the nail root move up to the surface of the skin, they increase in number, and also those closest to the nail root become flattened and also pressed strictly together. Every cell is transformed into a slim plate; these plates room piled in great to kind the nail. As with hair, pond are created by keratinization. As soon as the nail cells accumulate, the nail is thrust forward.


The skin listed below the nail is dubbed the matrix. The larger component of the nail, the nail plate, watch pink because of the network of tiny blood vessels in the basic dermis. The whitish crescent-shaped area in ~ the base of the nail is referred to as the lunula.

Fingernails grow about three or four times as easily as toenails. Prefer hair, nails grow an ext rapidly in summer than in winter. If a nail is take it off, it will regrow if the matrix is no severely injured. White point out on the nail space sometimes due to temporary transforms in development rate.

Skin Problems

Some that the points that can affect the skin, nails, and also hair are described below.


Medical professionals use the ax dermatitis (pronounced: dur-mah-ty-tus) to refer to any kind of inflammation that can be connected with swelling, itching, and also redness that the skin. There are many types of dermatitis, including:

Contact dermatitis occurs when the skin come into contact with an irritating substance or a substance that a human being is allergy to. The best-known reason of contact dermatitis is toxicity ivy. Yet lots of various other things cause contact dermatitis, consisting of chemicals found in wash detergent, cosmetics, and perfumes, and metals prefer jewelry, nickel plating ~ above a belt buckle, or the earlier of the buttons on her jeans.Seborrheic dermatitis, an oily decision on the scalp, face, chest, and back, is related to an overproduction that sebum from the sebaceous glands. This problem is usual in teens.Bacterial Skin Infections

Fungal Infections

Fungal epidemic of the Skin and NailsCandidal dermatitis. A warm, moist environment, such as that uncovered in the crease of the skin in the diaper area of infants, is perfect for growth of the yeast Candida. Yeast infections of the skin in enlarge children, teens, and adults are less common.

Other Skin Problems

Acne (acne vulgaris). Acne is the solitary most usual skin problem in teens. Some level of acne is checked out in 85% that adolescents, and practically all teens have the sometimes pimple, blackhead, or whitehead.Skin cancer. Skin cancer is rare in children and teens, but great sun protection actions established during these year can assist prevent skin cancers favor melanoma (pronounced: meh-luh-no-ma, a serious kind of skin cancer that deserve to spread to other parts that the body) later in life, especially amongst fair-skinned people who sunburn easily.

In addition to this diseases and also conditions, the skin have the right to be hurt in a number of ways. Young scrapes, cuts, and also bruises heal conveniently on your own, yet other injuries — significant cuts and also burns, for example — require clinical treatment.

Disorders the the Scalp and also Hair

Tinea capitis, a kind of ringworm, is a fungal infection that develops a scaly, ring-like lesion in the scalp. It’s contagious and common amongst school-age children.

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Alopecia (pronounced: ah-luh-pee-sha) is one area of hair loss. Ringworm is a common cause of momentary alopecia in children. Alopecia can additionally be brought about by chop braiding the pulls on the hair roots (this condition is referred to as traction alopecia). Alopecia areata (where a person’s hair drops out in round or oval patches on the scalp) is a less common condition that have the right to sometimes affect teens.

Reviewed by: Yamini Durani, MDDate reviewed: might 115