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Integumentary System Scratching the Surface Our Largest Organ… • Major functions include: – Protection – prevents chemical and physical injury – Sensory response – Vitamin D formation – Regulate body temp. – Rids the body of waste Contains 3 layers Epidermis Dermis Subcutaneous (fatty) layer Epidermis • • • The thinnest, outermost layer Epidermis cells are constantly being replaced Produces the chemical melanin – A pigment that protects your skin and gives it color. – Production increases when exposed to UV rays and skin becomes darker – Darker skin = greater protection Dermis and Subcutaneous • Dermis – Thicker layer located directly below the epidermis – Contains blood vessels, nerves, muscles, oil and sweat glands • Subcutaneous – Below the dermis – Fatty region that insulates the body – Where most fat is deposited when we gain wait. Vitamin D Formation • Small amounts are produced in the presence of UV light. • Vitamin D helps your body absorb calcium into your blood from food in your digestive tract. Heat Exchange • Blood vessels help release or hold heat – When they dilate (expand) blood flow increases and heat is released – When they constrict (shrink) blood flow decreases and less heat is released Heat Exchange • Sweat glands – When blood vessels dilate, pores open in the skin that lead to sweat glands – Perspiration moves out onto the skin, and heat transfers from the body to the sweat on the skin Waste Exchange • Sweat glands also release waste products produced by your cells – Water, salt, and other organic wastes • If too much water and salt are released, you can become dehydrated Injury and Repair • Bruises (contusions) – Tiny blood vessels under the skin burst – Red blood cells leak into the surrounding tissue – Hemoglobin from the red blood cells begins to breakdown into different pigments, giving bruises their different colors Broken down blood returns to bloodstream Injury and Repair • Cuts – – – – Any tear in the skin Blood clots and forms a scab Surrounding cells fight off infection Skin cells beneath the scab grow to fill the gap in the skin – Scars may result from thick tissue fibers if a cut is too deep. Injury and Repair • Skin grafts – Pieces of skin that are cut from one part of the body and moved to cover the injured area – Nearby blood vessels keep the grafted skin alive – Used when not enough skin cells are left
