Skin, Hair And Nails
Skin is a very important organ to the human body system. Skin keeps out pathogens, dirt, and unknown substances out of the body. It also keeps in water, so we don't dehydrate. Skin also lets out wastes. The skin has glands under it call sweat glands (see urinary system). Several wastes and chemicals can be excreted from the sweat glands.
There are three layers of skin. The epidermis is the surface layer of cells. This is the layers that keep out foreign bodies. The dermis is the next layer down. The epidermis is only about two sheets of paper think throughout the body. The dermis is mostly made out of muscle fibers. This lets the skin be flexible without ripping. The dermis is where nerve fibers, blood vessels, sweat glands, oil glands and hair follicles are. Skin and hair both get colored by melanin.
Your hair and nails are also a part of the integumentary system. Both hair and nails are made of living and dead cells. Hair follicles, which are found in the dermis is the living part of the hair.
As you add new cells to the hair, the old ones die. The same happens with your nails, but not in a hair follicle, in your nail bed. Hair keeps UVA rays from directly hitting the skin.
Uva rays can cause the skin cells to be damaged, and can even cause skin cancer. That's drastic, usually, we just get cuts and scrapes, and fortunately, our skin can heal itself. A blood clot forms with platelets (see cardiovascular system) and stops the bleeding. White blood cells will protect the area from outside bacteria, fighting off the pathogens. Damaged cells are replaced, and then a scar shows up. The scar is the newer cells that have come in.
Another bad thing that can happen to your skin is acne. Acne is very common in teens. Your body is producing to much oil, and the oil clogs hair follicles as well as sweat. They combine with bacteria and then create a zit or a pimple. This can be prevented by cleaning your face very well every day.
