Functions of Skin
Your skin covers the entire outside of your body. Your skin is your body’s largest organ yet
it is only about 2 mm thick. It has many important functions, some of these include:
- It acts as a barrier. It keeps organisms that could harm the body out. It stops water
from leaving the body, and stops water from getting into the body. - It helps regulate body temperature. It does this by making sweat, a watery substance
which cools the body when it evaporates. - It helps you to gather information about your environment. Special nerve endings in
your skin sense heat, pressure, cold and pain. - It helps the body get rid of some types of waste, which are removed in sweat.
- It acts as a sun block. A chemical calledmelaninis made by certain skin cells when
they are exposed to sunlight. Melanin blocks sun light from getting to deeper layers
of skin cells, which are easily damaged by sun light.
Structure of Skin
Your skin is always exposed to your external environment so it gets cut, scratched, and worn
down. You also naturally shed many skin cells every day. Your body replaces damaged or
missing skin cells by growing more of them. The layer of skin that you can see is actually
dead. The dead cells are filled with a tough, waterproof protein calledkeratin. As the dead
cells are shed or are removed from the upper layer, they are replaced by the skin cells below
them.
As you can see inFigure16.6, two different layers make up the skin. These layers are the
epidermisand thedermis. A fatty layer, calledsubcutaneous tissue, lies under the
dermis, but it is not part of your skin. The layers that make up your skin are shown in
Figure16.6.
The color, thickness and texture of skin vary over the body. There are two general types of
skin; thin and hairy, which is the most common type on the body, and thick and hairless,
which is found on parts of the body that experience a lot of friction, such as the palms of
the hands or the soles of the feet.
Epidermis
Epidermisis the outermost layer of the skin. It forms the waterproof, protective wrap over
the body’s surface and is made up of many layers ofepithelialcells (discussed in lesson 1).
The epidermis is divided into several layers where epithelial cells are formed by mitosis in
the lowest layer. The epithelial cells move up through the layers of the epidermis, changing
shape and composition as they divide and become filled with keratin. The skin cells at the