The Skin

Your Largest Organ The skin is your body’s LARGEST organ! Fun Facts: The average person's skin covers an area of 2 square meters.  Skin accounts for about 15% of your body weight. The average adult has approximately 21 square feet of skin, which weighs 9 lbs and contains more than 11 miles of blood vessels.

Skin Structures Made up of 3 layers of tissue Epidermis Dermis Fatty Layer

Epidermis Outer, thinnest layer of your skin Outermost cells are dead and water repellent 1,000s of epidermal cells rub off every time you take a shower, shake hands, blow your nose, etc. New cells are produced constantly at the base of the epidermis

Epidermis Continued… Cells in the epidermis produce the chemical melanin. Melanin is a pigment that protects your skin and gives it color (your eyes, too). Different amounts of melanin results in different skin colors When skin is exposed to UV rays, melanin production increases and skin becomes darker Lighter skin tones = less protection = burns more easily

Dermis The layer of cells directly below the epidermis Thicker than the epidermis Contains blood vessels, nerves, muscles, oil and sweat glands Below dermis is the fatty region that insulates the body This is where much of the fat is stored when a person gains weight

Dermis Continued… Blood vessels: a tubular structure carrying blood through the tissues and organs Nerves: special cells that carry messages from one part of the body to another Oil glands: a small gland that secretes an oily or waxy matter to lubricate and waterproof the skin and hair of mammals. Sweat glands: a small gland that secretes sweat and excretes waste

Skin Functions Protection = Most important function Sensory response Special nerve cells detect and relay information to the brain, which makes your skin a sensory organ This is why you can sense the softness of a blanket, sharpness of a needle, heat of a frying pan, etc. Formation of vitamin D Small amounts of vitamin D are produced when your skin is exposed to UV light (sunlight) Essential for good health Helps body absorb calcium into blood from food in digestive tract Skin forms a protective covering over the body that prevents physical and chemical injury. Some bacteria and other disease-causing organisms cannot pass through the skin as long as it is unbroken. Glands in the skin secrete fluids that can damage or destroy some bacteria. The skin also slows down water loss from body tissues.

Skin Functions Continued… Regulation of body temperature Blood vessels help release or hold heat Blood vessels expand blood flow increases heat is released Blood vessels contract blood flow decreases less heat is released Adult human dermis has about 3,000,000 sweat glands These help regulate body temperature and excrete wastes Blood vessels dilate - pores open in the skin that lead to the sweat glands - sweat then moves out onto the skin – heat transfers from body to sweat on the skin – sweat evaporates – removes the heat and cools the skin. Eliminates excess heat produced by muscle contractions

Skin Functions Continued… Ridding the body of wastes As your cells use nutrients for energy, they produce wastes If not removed from your body, these wastes can act as poisons Sweat glands also release water, salt and other waste products If too much water and salt are released by sweating, you might feel light-headed or may faint

Skin Injuries and Repair A bruise is the bursting of the tiny blood vessels beneath the skin Red blood cells leak into surrounding tissue These blood cells break down and release hemoglobin Hemoglobin breaks down into pigments The color of these pigments causes bruised area to turn shades of blue, red and purple After all pigment is absorbed into the bloodstream, the bruise disappears and skin looks normal

Cuts A cut is any tear in the skin Blood flows out, then a clot forms over it Scab forms to prevent bacteria from entering the body Scab falls off, leaving new skin behind Cells in surrounding blood vessels fight infection while the skin cells beneath the scab grow to fill the gap in the skin Scars form when a cut is big enough and it’s the large amounts of thick tissue fibers that form