Life Science: 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

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.

Multiple Choice

What is the outer layer of the skin called?

• Epidermis

• Dermis

Multiple Choice

True or False?

Light scratches on the epidermis layer can bleed

• True

• False

Multiple Choice

Does the epidermis contain nerves or blood vessels?

• Yes

• No

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.

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.