http://www.ck12.org Chapter 1. Human Biology
Some people put a lot of time and money into maintaining their skin. They may use special creams and lotions.
While expensive creams may not be necessary, it is a good idea to take care of your skin. It does a lot of things for
you, from protecting you from disease to sensing your environment.
Your Skin
Did you know that you see the largest organ in your body every day? You wash it, dry it, cover it up to stay warm,
and uncover it to cool off. Yes, your skin is your body’s largest organ.
Your skin is part of yourintegumentary system(Figure1.4), which is the outer covering of your body. The
integumentary system is made up of your skin, hair, and nails.
Functions of Skin
FIGURE 1.
Skin acts as a barrier that stops water
and other things, like soap and dirt, from
getting into your body.The skin has many important functions. The skin:
- Provides a barrier. It keeps organisms that could harm the body out. It stops water from entering or leaving
the body. - Controls body temperature. It does this by making sweat (orperspiration), a watery substance that cools the
body when it evaporates. - Gathers information about your environment. Special nerve endings in your skin sense heat, pressure, cold,
and pain. - Helps the body get rid of some types of waste, which are removed in sweat.
- Acts as a sun block. A pigment calledmelaninblocks sunlight from getting to deeper layers of skin cells,
which are easily damaged by sunlight.
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. Did you know that the layer of skin you can see is actually dead? As the dead cells are shed or removed from
the upper layer, they are replaced by the skin cells below them.