Integumentary System Biology Grade-9

1. Integumentary SystemBiology Grade-9 Prepared by the teacher: Ronak Ahmed Hassan 2012-2013 International School / Duhok

2. - Is there a partly dead part in your body? - Is it important to keep you alive? Here are some clues: • It comes in many colors. • It is the largest organ in the body. • It is showing right now! Now, what do you guess?........ Your skin, hair, and nailsmake up your integumentary system. Nails Hair Skin What is the function of integumentary system? Covers your body and helps you maintain homeostasis.

3. Functions of Skin • Skin protects you by keeping water in your body & foreign particles out of your body. • Skin keeps you in touch with the outside world. Nerve endings in your skin let you feel things around you. • Skin helps regulate your body temperature. Small organs in the skin called sweat glands make sweat. Sweat is a salty liquid that flows to the surface of the skin. As sweat evaporates, the skin cools. • Skin helps get rid of wastes. Several kinds of waste chemicals can be removed in sweat.

4. Why there is different color of skin ? It determined by a chemical called melanin. If a lot of melanin is present, skin is very dark If little melanin is present, skin is very light What is the importance or the role of melanin? Melanin absorbs ultraviolet light from the sun. So melanin reduces damage that can lead to skin cancer Can we say only light skin is vulnerable to cancer? No, all skin, even dark skin, is vulnerable to cancer. Skin should be protected from sunlight whenever possible.

5. Structure of the skin Beneath the surface, your skin is a complex organ made of blood vessels, nerves, glands, and muscles. Oil glands: release oil that keeps hair flexible & waterproofs the epidermis. Epidermis Carry messages to and from the brain In the dermis make hair Dermis Muscle fibers: Attached to hair follicle can contract & cause the hair to stand up Fat cells Transport substances & help regulate body temperature Release sweat to cool the body. Sweating is also a way to remove waste materials from the body.

6. Skin Layers of Skin What is the largest organ of your body? The skin of an adult covers an area of about 2m 2 You see it when you look at your skin

7. Epidermis • The epidermis is made of epithelial tissue. • Even though it has many layers of cells, it is as thick as only two sheets of paper over most of the body. 1- On the palms of your hands. 2- on the soles of your feet Where is it thicker? Most cells in the epidermis are dead These cells are filled with a protein called Keratin. What is the function of Keratin? Keratin helps make the skin tough.

8. Dermis The dermis lies beneath the epidermis It has many fibers made of a protein called collagen What is the function of these fibers? • provide strength. • let skin bend without tearing Self- Check Describe the dermis. How does it differ from the epidermis? The dermis is the layer of skin that lies beneath the epidermis. It is composed of a protein called collagen, while the epidermis contains keratin.

9. Hair and Nails They are important parts of the integumentary system Like skin, hair & nails are made of living and dead cells Where the hair & nails are formed? The hair forms at the bottom of a tiny sac called a hair follicle. The nail grows from living cells in the nail root at the base of the nail. When the hair grow, where the new cells will be added to? When the hair grows, a new cells are added at the hair follicle. Older cells get pushed upward. What part of hair is the living part and which one is dead? The only living cells in a hair are in the hair follicle. The rest are dead part

10. Melanin The reason of different color of hair is due to the…. What are the functions of hair? • Hair helps protect skin from ultraviolet light. • It keeps particles, such as dust & insects, out of your eyes and nose. • In most mammals, hair helps regulate body temperature. How hair contribute in the regulation of body temperature? A tiny muscle attached to the hair follicle contract. If the follicle contains a hair, the hair stands up. The lifted hairs work like a sweater. They trap warm air around the body.

11. How nails become longer? It became longer as new cells form. The nail’s function: • Nails protect the tips of your fingers and toes. So, your fingers and toes can be soft and sensitive for a keen sense of touch. What is the content of the hair? A hair is made up of layers of dead, tightly packed, keratin-filled cells.

12. Skin injuries • Skin cancer • Acne. Skin is often damaged. Fortunately, your skin can repair itself. What is the causes of skin cancer? If the damage of skin was in the genetic material in skin cells, this can cause skin cancer. What is the causes of acne? Skin may also affected by hormones that causes oil glands in skin to make too much oil. This oil combines with dead skin cells & bacteria to clog hair follicles which causes acne.

13. How Skin Heals Describe how a cut heal? • A blood clot forms over a cup to stop bleeding and to keepbacteria from entering the wound. Bacteria-fighting cells then come to the area to kill bacteria. • damaged cells are replaced through cell division. Eventually, all that is left on the surface is a scare.

14. Self-Check Describe how nails grow. • New cells are produced in nail root, just beneath the lunula. The new cells push older cells toward the outer edge of the nail.