Now switching gears from the structure of the
skin, let's talk about the functions of the skin.
There are 6 different functions
associated with the skin.
We have as thermal regulation, a blood
reservoir, protection, cutaneous sensations,
excretion and absorption
and synthesis of vitamin D.
The first function of the
skin is thermoregulation.
Thermoregulation involves the maintenance of
homeostasis by maintaining the body's temperature.
For example, if we get
very hot, our body will sweat
and then the sweat will allow the
cooling of the surface of our body
due to the evaporative properties of water.
Conversely, if we get very cold, we
can increase blood flow to the dermis
in order to heat up the skin.
The skin also serves as a major
blood reservoir and interestingly,
the dermis has so many blood
vessels that it actually holds
about 10% of the total blood
flow while an adult is at rest.
The third function of the skin is protection.
it uses multiple ways of protecting
things from getting inside the body.
First, it uses keratin, lipids, sebum
and acidic sweat to block bacteria
and other microbes from
getting into the body.
Melanin is used to block UV rays from
damaging the DNA inside of our cells.
And macrophages are specialised
cells that actually engulf and eat bacteria
that are trying to get into the body.
A fourth function of the
skin is cutaneous sensations.
Recall that it's very important for organisms
to be able to respond to their environment.
The skin contains different
types of sensory receptors
that are found in
different layers of the skin.
So for tactile sensations such as
touch, pressure vibration and tickle,
we have nerve endings found in
the papillary layer of the dermis.
We also can detect sensations such
as warm and cool, or thermal sensations.
Finally, pain can also be detected
by nerve endings found in the dermis.
The fifth function of the skin
is excretion and absorption.
We are able to eliminate some
substances from the body through the skin.
As well, we are able to
absorb some substances
from the external environment
into the body cells through the skin.
An example of this is
transdermal drug administration.
So if you've ever heard of the birth
control patch or the nicotine patch,
this actually delivers
drugs through the skin.
The final function of the scan and a very important
function of the skin is the synthesis of vitamin D.
Ultraviolet rays from the sun activate
the precursor molecule known as calcitriol
that allows for our vitamin D
to be made in our body.
Vitamin D is absolutely essential
for the absorption of calcium
that we intake from our food
into our gastrointestinal tract.
From there, it can be used for building bone and for
other processes in the body that require calcium.