• Epidermis

• Melanin

• Dermis

• Pore

• Follicle

• Cancer

​Vocabulary

• What are the functions and the structures of your skin?

• What habits can help keep your skin healthy?

​Key Concepts

The Skin

The skin is made up of two main layers. The top layer is called the epidermis. The bottom layer is called the dermis.

In which layer of the skin do you find blood vessels?

The Skin

Answer:

If your answer is the skin, you are right! If an adult's skin were stretched out flat, it would cover an area larger than 1.5 square meters, which is about the size of a mattress on a twin bed. You may think of the skin as nothing more than a covering that separates the inside of the body from the outside environment. If so, you'll be surprised to learn about the many important roles that the skin plays.

The Epidermis

The skin is organized into two main layers. The epidermis is the outer layer of the skin. In most places, the epidermis is thinner than the dermis. The epidermis does not have nerves or blood vessels. This is why you usually don't feel pain from light scratches, and why light scratches do not bleed.

Discover Activity

What Can You Observe About Skin?

1. Using a magnifying glass, examine the skin on your hand. Look for pores and hairs on both the palm and the back of your hand.

2. Discuss your observations

The Body's Tough Covering

The Skin Performs Several Major Functions in the Body

The skin covers and protects the body from injury, infection, and water loss. The skin also helps regulate body temperature, eliminate wastes, gather information about the environment, and produce vitamin D.

The skin protects the body by forming a barrier that keeps disease-causing microorganisms and harmful substances outside the body. In addition, the skin helps keep important substances inside the body. Like plastic wrap that keeps food from drying out, the skin prevents the loss of important fluids such as water.

​Protecting the Body

Epidermis Structure

Like all cells, the cells in the epidermis have a life cycle. Each epidermal cell begins life deep in the epidermis, where cells divide to form new cells. The new cells mature and move upward in the epidermis as new cells form beneath them. After about two weeks, the cells die and become part of the epidermal surface layer. Under a microscope, this surface layer of dead cells resembles flat bags laid on top of one another. Cells remain in this layer for about two weeks. Then, they are shed and replaced by the dead cells below.

Another function of the skin is to help the body maintain a steady temperature. Many blood vessels run throughout the skin. When you become too warm, these blood vessels enlarge and the amount of blood that flows through them increases. These changes allow heat to move from your body into the outside environment. In addition, sweat glands in the skin respond to excess heat by producing perspiration. As perspiration evaporates from your skin, your skin is cooled.

Maintaining Temperature

Epidermis Function

In some ways, the cells of the epidermis are more valuable dead than alive. Most of the protection provided by the skin is due to the layer of dead cells on the surface. The thick layer of dead cells on your fingertips, for example, protects and cushions your fingertips. Also, the shedding of dead cells carries away bacteria and other substances that settle on the skin. Every time you rub your hands together, you lose thousands of dead skin cells and any bacteria on them.

Epidermis Function (continued)

Some cells in the inner layer of the epidermis help to protect the body. On your fingers, some cells produce hard fingernails, which protect the fingertips from injury and help you scratch and pick up objects.
Other cells deep in the epidermis produce melanin, a pigment, or colored substance, that gives skin its color. The more melanin in your skin, the darker it is. Exposure to sunlight stimulates the skin to make more melanin. Melanin production helps protect the skin from burning.

Perspiration contains dissolved waste materials that come from the breakdown of chemicals during cellular processes. Thus, your skin is also helping to eliminate wastes whenever you perspire. For example, some of the wastes that come from the breakdown of proteins are eliminated in perspiration.

Eliminating Wastes

The skin also gathers information about the environment. To understand how the skin does this, place your fingertips on the skin of your arm and press down firmly. Then lightly pinch yourself. You have just tested some of the nerves in your skin. The nerves in skin provide information about such things as pressure, pain, and temperature. Pain messages are important because they warn you that something in your surroundings may have injured you

Gathering Information

Lastly, some of the skin cells produce vitamin D in the presence of sunlight. Vitamin D is important for healthy bones because it helps the cells in your digestive system to absorb the calcium in your food. Your skin cells need only a few minutes of sunlight to produce all the vitamin D you need in a day.

Producing Vitamin D

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RETURN TO YOUR PROPER POSITIONS AND ANSWER THE REMAINING QUESTIONS ON YOUR OWN