Lesson 10 February 14 th, 2011

Skin Your skin the largest organ in the body, unlike other organs such as the heart, lungs and kidneys, you skin acts as a boundary between you and the outside world.

Functions of Skin: Protects inner cells Shields the body from harmful solar rays Defence against germs The bodies first line of defence Senses the external environment 4 Types of nerve cells Insulator in cold weather Helps to release heat by sweating Produces Vitamin D in sunlight

Layers of the skin: Outer layer is called the Epidermis Inner layer is called the Dermis

Blisters are caused when the two layers separate and the space is filled with fluid

Epidermis is made of two layers: 1. Stratum corneum - dead skin, 2. Stratum germinativum - layer which produces new cells. Keratin is a substance that hardens and makes skin waterproof Melanin is a pigment which is produced in the epidermis. Melanin colours or tans the skin.

Dermis contains: Touch receptors (for pain and pressure) Glands (oil and sweat) Hairs in follicles Fat cells Blood vessels

Where the two layers (dermis and epidermis) meet a wavelike pattern is produced fingerprints.

Nails are hard convex structures. They are made by the epidermis and keratin replaces the cytoplasm in the cells to make them hard. Hair is produced in follicles found in the dermis. When hairs are touched the nerve endings at the base of the hair are triggered by the motion.

Skin Care Wash frequently Clean wounds Treat burns seriously Don’t touch blemishes (pimple, spots) Proper diet: fruit, vegetables, and water. Healthy skin contains around 10% moisture.

Skin Care Skin cleansing is necessary for skin health, hygiene and well being. Without effective cleansing, your skin’s surface can accumulate debris, sweat, air pollution, excess oil and bacteria. Cleaning the skin also helps to reduce the growth of microorganisms and reduce infection. Washing with water alone will rinse some of the dirt and debris away, alone it’s not quite enough. Plain tap water will only remove about 65 percent of the oil and dirt on your skin, and will not effectively remove makeup. Skin cleansers, however, work as emulsifiers and help remove dirt, excess sebum (natural skin oils), bacteria, cosmetics and exfoliated surface skin cells.

Skin care Where Dirt and Debris Collect When we cleanse our skin, we’re targeting the outermost layer of the skin called the epidermis. This outermost layer of the epidermis is composed of a tough protein-fat structure that produces a protective outer film, the skin moisture barrier. Part of the function of the epidermis is to waterproof the skin. While this film shields skin cells from the environment, it also traps and holds dust, pollutants, smoke, bacteria, cell debris, sweat and cosmetics. Washing the embedded dirt off of your skin also removes some of this outer protective film and can irritate your skin, although mild cleansers have been developed to restore and maintain this protective covering.

Hair Care Wash and brush hair regularly Massage the scalp Have a balanced diet limit exposure to sunlight which makes hair brittle choose the correct pH balanced shampoo or hair will be damaged

Sunlight The three types of UV radiation are UV-A, UV-B and UV-C. UV-C is the most dangerous. UV radiation causes: Causes the skin to produce more melanin (tan) Burns the skin Can cause skin cancer

Explanation for the lab Water evaporates at room temperature and the warmer it is the faster it evaporates. Oil needs to be at a much higher temperature to evaporate. If there is a layer of oil on water the water will not evaporate. Your skin produces an oil that forms a film on your skin’s surface. The oil works in much the same way as the layer of oil in the beaker that contained the oil. Skin creams can help put moisture back into the skin and add a film of oil to the surface of the skin.

Questions: How does a layer of oil on the skin hold in moisture? It helps prevent the water from evaporating What are two things that skin creams do? Moisturizes the skin Adds a protective oil layer

How do sunscreens work? There are three forms of sunlight: infrared (heat) rays, visible light rays, and ultraviolet (UV) rays. UV rays can burn and damage your skin, even on a cloudy day or while swimming outside. When you cover up with a hat and thick clothes, you protect your skin from UV rays. Sunscreen can help protect your exposed skin from UV rays. Physical sunscreens such as zinc oxide leave a visible layer on your skin that reflects UV rays. Chemical sunscreens absorb the UV rays. Chemical sunscreens usually cannot be seen after you rub them in.

The effectiveness of a chemical sunscreen is shown by a number called the Sun Protection Factor (SPF). SPF is the measure of how much longer you can stay in the sun without burning. Example: If your skin usually burns in 10 minutes, an SPF 15 sunscreen would allow you to stay in the sun 15 times longer, or 150 minutes.

Questions Explain the difference between a physical and chemical sunscreen. If you usually burn in 20 minutes, how much longer could you stay in the sun if you covered your skin with SPF 30 sunscreen? ________Min x SPF___________=_____________minutes Why do you think it’s recommended to apply a chemical sunscreen about half an hour before going out in the sun?