S TRUCTURE AND FUNCTIONS OF THE SKIN

L AYERS OF THE SKIN The skin is the largest organ of the body. This elastic, protective covering is thinnest on the lips and eyelids and thickest on the palms and soles. Its made up of hundreds of layers that are compacted into three layers. 1. The epidermis, this is the outermost layer of skin which provides a waterproof barrier and creates our skin tone. 2. The dermis, this layer is beneath the epidermis and contains tough connective tissue, hair follicles and sweat glands. 3. Subcutaneous layer (hypodermis) is made of fat and connective tissue The skins colour is created by cells called melanocytes, these cells produce the pigment melanin and are located in the epidermis

C ROSS SECTION OF THE SKIN

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F UNCTIONS OF THE SKIN S - s ensation H - h eat regulation A - a bsorption P - p rotection E - e xcretion S – s ecretion Vitamin D production

F UNCTIONS OF THE SKIN Sensation – there are five types of nerve ending within the skin to help identify pain, touch, heat, cold and light pressure Heat regulation – The skin helps regulate the body's temperature by sweating to cool the body when it overheats and shivering when its cold. Hot: The sweat glands in the body release more sweat when hot which evaporates. This removes heat energy from the skin. Blood vessels leading to capillaries become wider (dilate) allowing more blood to flow through the skin and more heat to be lost. Cold : Our muscles contract rapidly when we are cold which causes us to shiver. Blood vessels leading to capillaries become narrower (constrict) letting less blood through the skin and conserving heat in the body. Shivering closes the pores, and the arrector pili muscle attached to the hair contracts causing the hair to stand on end (goose bumps) to trap a layer of warm air next to the skin, which helps to prevent against heat loss.

F UNCTIONS CONTINUED … Protection – The skin is the first barrier we have against outside aggressions. The skin contains a pigment called melanin that protects us from UV light. When we are exposed to UV light more melanin is produced and this is what gives us a suntan. We also have an acidic layer (acid mantle) on the surface of the skin which protects us against bacterial infections. Sebum (oil) is produced by the sebaceous gland and this waterproofs our skin Absorption – some creams, essential oils and medications can be absorbed through the skin via the hair follicles. Ultra violet rays are also absorbed which aid in the production of vitamin D which is essential for the production of healthy bones and eyes.

F UNCTIONS CONTINUED … Secretion – Sebum and sweat are secreted onto the skins surface. The sebum (oil) keeps the skin lubricated and soft. Sweat combines with the sebum to form the acid mantle. Excretion – waste products and toxins such as water and salt are removed from the body via the sweat glands

C ROSS SECTION OF THE EPIDERMIS In pairs you will be assigned one layer of the epidermis. Identify the Latin name for your layer and complete the function of the layer you are given. Feedback answers to the rest of the group. Task

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C IRCULATION Blood is transported around the body via the circulatory system Composition of blood = 55% plasma 45% blood cells Plasma is a yellow, transparent fluid made up of mostly water with a small amount of protein present. There are 3 types of blood cells: Red – transport oxygen to cells take away carbon dioxide White – protect body against invading bacteria help form immune system Platelets – play important role in blood clotting Oxygenated blood and nutrients are carried away from the heart via the arteries Deoxygenated blood is carried back to the heart via the veins A rteries = A way Ve in = In

C IRCULATION OF THE HAND AND ARM bwa palmar dwfn rhydweli rheiddiol ulnar rhydweli rhydweli brachial gwythïen seffalig gwythïen basilic gwythïen cubital canolrif

B LOOD VESSELS IN THE HAND AND ARM Cephalic vein Median cubital vein Brachial artery Basilic vein Ulna vein Median vein Ulna artery Metacarpal artery Digital artery Radial artery