The Skin (aka the Integumentary System)

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Fun Facts About The Skin

• The skin is the largest organ in the human body.

• It weighs about 8-10 pounds.

• It is a tough but flexible outer covering.

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Functions of the Skin

1. Provides a physical barrier that protects internal organs from pathogens

2. Protects us from radiation, chemicals, and harmful substances in our environment

Functions of the Skin

3. Keeps body fluids in to prevent drying out (desiccation)

4. Helps maintain proper body temperature

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Functions of the Skin

5. Contains nerve endings that give us information about the environment (hot, cold, touch, pressure, pain)

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Layers of the Skin

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1. The Epidermis

• Outer layer (the layer you can see)

• Made up of dead or dying cells

• Upper layer is called the horny layer; made up of dead epithelial cells that constantly rub off

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1. The Epidermis

• Lower layer is made up of living cells that are constantly dividing and rising to the surface, replacing old worn-off cells

• Hair and nails form from epidermal cells

• Does not have its own blood supply

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2. The Dermis (true skin)

• Thicker than the epidermis and contains blood vessels

• Contains sweat and oil glands, nerves, and the roots of hairs

• Sweat glands keep the skin cool

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2. The Dermis (true skin)

• Nerve receptors send messages of pain, pressure, touch, hot, and cold to the brain

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3. Subcutaneous Layer

• Connects skin to muscle

• Has fat to provide insulation, padding, and a reserve source of energy

• Connective tissue in skin makes it elastic

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Skin Color

• Melanin: pigment that gives the skin its color. More melanin is produced in response to sunlight to protect the cells from damage.

• Blood flow: the more blood in the skin, the redder the skin

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Sunburns

• The sun’s UV rays damage the outer skin’s cells; the body sends blood to the damaged cells to repair them. This results in red skin.

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Skin Cancer

• Believed to be caused by ultraviolet rays of the sun.

• Protection: 1. Sunscreen2. Cover up3. Limit exposure4. Avoid tanning booths

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Great Microorganisms of the World

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1. Fungi

• Made up of many cells with long, thin strands

• Grow on agar• Usually decomposers:

they live on dead tissue or animal wastes

• Examples: molds, yeast, mushrooms

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2. Bacteria

• Single cells that may be round, rod-shaped, or spiral-shaped

• Can be seen with a light microscope

• Grow on agar• Form colonies when

they reproduce• Decomposers

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3. Viruses

• Small; can only be seen with an electron microscope

• Not made of cells• Can only grow and

reproduce in a living cell

• Cause colds, flu, measles, and mumps

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