The Integumentary System

Transcription

1 The Integumentary System

2 THE INTEGUMENTARY SYSTEM Skin is the system of the body that makes an individual beautiful! Skin/fur coloration allows animals to be camouflaged. *The skin is the largest organ of the body. The skin and its derivatives (hair, nails, sweat and oil glands) make up the integumentary system. The total surface area of the skin is about 1.8 m² and its total weight is about 11 kg. The skin gives us our appearance and shape. Anatomy of the Skin Skin is made up of two layers that cover a third fatty layer. The outer layer is called the epidermis; it is a tough protective layer. The second layer (located under the epidermis) is called the dermis; it contains nerve endings, sweat glands, oil glands, and hair follicles. Under these two skin layers is a fatty layer called the subcutaneous tissue, or hypodermis. 1

3 The dermis is home to the oil glands. These are also called sebaceous glands, and they are always producing sebum. Sebum is your skin's own natural oil. It rises to the surface of your epidermis to keep your skin lubricated and protected. It also makes your skin waterproof. Skin is alive! It's made of many thin sheets of flat, stacked cells. Older cells are constantly being pushed to the surface by new cells, which grow from below. When the old ones reach the top, they become wider and flatter as they get rubbed and worn by all your activity. And, sooner or later, they end up popping off like tiles blown from a roof in a strong wind. In fact, every minute 30,000-40,000 dead skin cells fall from your body! In approximately a month's time, your body has made a whole new layer of skin cells! Melanin is found in the epidermis and is the pigment that gives skin and hair its color. It also protects against the rays of the sun. Darker colors have more melanin. The Functions of the Skin Control of body temperature (thermoregulation) Keeping out infection Waterproof barrier Protection of delicate tissues underneath Mending itself when damaged Thermoregulation (the ability to maintain the body s correct temperature) When the skin is exposed to cold temperature, the blood vessels in the dermis constrict. This allows the blood which is warm, to bypass the skin. Body heat is conserved since the blood vessels are not diverting heat to the skin anymore. If the body is too hot, the blood vessels leading to the skin capillaries dilate (get larger). This is known as vasodilation. This allows lots of blood to 2

4 flow near the surface and heat is lost through the skin. To further reduce the body temperature, sweating occurs. Sweat is mostly water with some salt (sodium chloride). It is produced by the sweat glands and pours out onto the surface of the skin. Here the water evaporates, which removes heat from the skin therefore cooling the skin down. Salt is left on the skin so the skin can taste a bit salty after sweating. **Skin is responsible for the 5th sense, feeling. The sense of touch is one of our body's most important senses. Touch is detected by receptors in the skin. Many of these are found next to hair follicles so even if the skin is not touched directly, movement of the hair is detected. Touch receptors are not distributed evenly over the body. The fingertips and tongue may have as many as 100 per cm²; the back of the hand fewer than 10 per cm². Nails Composed of long fibers of the protein, keratin (the material from which your hair is made), nails protect the fingertips. They also aid in picking up objects in the same way that birds and animals use their beaks and claws to help them handle food or objects. Most animals have some form of nails. Many have sharpened, curved nails that we call claws. Ungulates have a thick, round stump of a fingernail that we call a hoof. Keratin is found on the outside of the nail or hoof, and the sensitive layers are inside. Hair How does hair grow? Hair is made at the base of a hair follicle. There are a thousand hair follicles on your head. Only about 80% of your follicles are producing hair at any one time. The rest of the follicles are asleep or dormant. When dormant hair follicles start working again, they push out an old hair while making a new 3

5 one. You could lose 50 to 100 hairs in any day. Some of us lose more than that and don t get them back again! Hair facts Average number of hairs on the head: 100,000 Red hair: 90,000 Black hair: 110,000 Blond hair: 140,000 Annual growth: 12 cm Female hair grows more slowly than male hair Male hair is more dense than female hair Lifespan of hair: 2 to 7 years Diameter of hair: 0.1 mm Load-carrying capacity: 100 grams (= one chocolate bar) Combing is less detrimental than brushing Hair grows faster in warm weather Elderly people have slower hair growth and diminished hair density Cutting hair does not influence its growth Spliced ends can not be repaired and need to be cut Common Injuries and Infections of the Skin Burns Burns can be caused by heat, chemicals, electricity, or radiation First-degree burns are red and painful. They turn white when you press on the skin. The skin over the burn may peel after 1-2 days. Thicker burns, called second-degree burns, have blisters and are painful. The skin is very red or splotchy, and it may swell a lot. Third-degree burns cause damage to all layers of the skin. The burned skin looks white or charred. These burns may cause little or no pain because the nerves in the skin are damaged. Sunburn is an inflammation of the skin that is caused by overexposure to ultraviolet (UV) radiation. 4

6 UV rays from the sun are most intense between 10 a.m. and 3 p.m., particularly in the late spring, summer, and early autumn. Mild sunburn only damages the outer layers. Severe sunburns can become 2nd degree burns, causing severe pain and blisters. *Why does the temperature of the skin feel hot when sunburned? The burned skin feels hot/warm because of the way the body responds to this type of injury. The immune system senses damage and calls for help. Help is delivered by increasing the blood flow to the region, essentially causing inflammation of the area. The increased blood flow to this area of the skin makes it feel warm and appear red. Naturally, this hot feeling will continue for as long as the area of skin is "under repair", which varies from person to person (a few days to perhaps weeks, depending on the severity of the sunburn). Sunburn prevention The UV rays that we are exposed to here on the earth's surface consist of UVB and UVA photons. A sunscreen product acts like a bulletproof vest, stopping the UV photons before they can reach the skin and inflict damage. It contains molecules that absorb UV and pigments that absorb, scatter and reflect UV. To deliver a high level of protection, a sunscreen product must have sufficient quantities to adequately cover the skin s surface. The term SPF that appears on sunscreen labels stands for Sun Protection Factor, but it is really a sunburn protection factor. Products with a higher SPF allow fewer of the photons that produce sunburn to strike the skin. In simple terms, you can view an SPF 10 sunscreen as allowing 10 out of every 100 photons to reach the skin and an SPF 20 product as allowing only 5 out of every 100 photons to reach the skin. Acne Acne is a skin condition that shows up as different types of bumps. They include whiteheads, blackheads, red bumps (pimples), and bumps that are filled with pus (called cysts). Our skin is covered with tiny holes called pores, which contain sebaceous glands (also called oil glands) that make sebum, an oil that moistens your hair and skin. Sometimes a pore gets clogged up with too much sebum, dead skin cells, and bacteria. This can cause acne. 5

7 If a pore gets clogged up, closes, and bulges out from the skin, that's a whitehead. If a pore clogs up but stays open, the top surface can get dark and you're left with a blackhead. Sometimes the walls of the pore are broken, allowing sebum, bacteria, and dead skin cells to get under the skin. This causes an infection called a pimple. *In case you are lucky enough to have never seen one, these are pimples. Acne Prevention To help prevent the oil buildup that can lead to acne, wash your face twice a day with warm water and a mild cleanser. Don't scrub your face. Scrubbing can actually make acne worse by irritating the skin. If you wear makeup, moisturizer, or sunscreen, make sure they are "oil-free," "noncomedogenic," or "nonacnegenic." If you use hair sprays or gels, try to keep them away from your face because they can clog pores. If you have long hair, keep it away from your face and wash it regularly to reduce oil. Baseball caps and other hats can cause pimples along the hairline. Avoid them if you think they are worsening your acne. Wash your face after you've been exercising and sweating a lot. Try not to touch your face. Don't pick, squeeze, or pop pimples. Acne treatments Many lotions and creams are sold at drugstores to help prevent acne and clear it up. You can try different ones to see which helps. Products with benzoyl peroxide or salicylic acid in them are usually pretty helpful for treating acne. Benzoyl peroxide kills the bacteria that can lead to acne and it also can reduce swelling (puffiness) of pimples. Salicylic acid is another acne-fighting ingredient. It causes skin to dry out and peel, which can help get rid of pimples, too. 6

8 When you use a product for acne, be sure to follow the directions exactly. Don't use more than you're supposed to because it can make your skin very red and very dry. It's also good to try just a little bit at first to be sure that you're not allergic to the product. Don't give up if you don't see results the next day. Acne medicine can take weeks or months to work. 7