Download Explanation Writing Sample

Why Do Humans Have Skin?
Skin is the largest and only external organ that covers the muscles,
bones and internal organs of the body. It is made up of 3 layers of
skin cells which are covered in hair. It stretches as the body grows.
It prevents bacteria and germs from entering the body. Skin can be
lots of different colours.
The skin acts as a barrier against dangerous things in the
environment, such as germs and bacteria, from entering the body,
which can cause infection.
Skin is an almost waterproof outer layer that repels water. It lets
water runoff the body. Skin stops the evaporation of bodily fluids
(which wash tissues within the body) and prevents the destruction
of cells.
The skin is our sense of touch. There are nerve endings on the skin
which enable a person to feel the texture and temperature of
objects or to feel pain.
The skin controls the body’s temperature and keeps it at a regular
37.5 degrees Celsius. If the body is too hot, the skin will excrete
water and salt through sweat glands in the skin, therefore, bringing
down the temperature of the body. If the body is too cold, blood
flow will reduce in an attempt to make the body work harder,
therefore, increasing body temperature. Also, the skin contracts
when the body is cold in an effort to retain heat.
The skin is like a factory because it produces more skin cells and
several chemicals. Melanin is a chemical produced in the skin that
makes the skin ‘tan’. The skin aids in the production of Vitamin D
when exposed to sunlight.
Skin protects underlying tissues from harmful UV rays.
The skin holds body parts in place and prevents movement of such
parts.
The skin acts like a sponge and absorbs oily substances.
The skin is made up of 3 layers of tissue, each with their own
important job.
1. The epidermis is the outer layer of skin that we can see and
touch. It is responsible for regulating the body’s temperature
and it is home to the cells that produce melanin. It prevents
body fluids from escaping and it protects the body from
germs. Its consistently making new skin cells, which when
ready, move to the top to make a new layer of skin. It does not
contain any blood vessels.
2. The dermis is the second layer of skin which cushions the body
from stress or strain. There are a lot of blood vessels in the
dermis, which keep the skin cells healthy by bringing oxygen
and nutrients to the cells. The dermis contains collagen and
elastin which give the skin its shape and its elasticity. It
contains nerve endings, sweat glands, oil glands and hair
follicles.
3. The subcutaneous layer (hypodermis/ hyperdermis) is the third
layer of skin which is made mostly of fat cells, which absorb
and retain heat. It also protects the internal organs from
injury and shocks. It attaches the skin to the underlying bone
and muscle.
Over 50% of dust in your home is dead skin. An adults average skin
spans 22 square feet, weighs 9 pounds and contains more than 11
miles of blood vessels. Skin is 15% of your body weight. The skin
loses 30-40 thousand dead skin cells per minute. The skin renews
itself every 28 days. Oily surfaces on the skin may contain over 500
million bacteria per sq inch. There is 45 miles of nerves in the skin.
In a lifetime, you would fill a 2 storey house with dead skin. Skin is
thickest on the sole of the foot (4mm) and it is thinnest on the
eyelid (0.02mm) Skin releases as much as 13.5L of sweat in hot
weather. On average 14 species of fungi live between your toes.
Skin conditions include warts, eczema, acne, cellulitis, verrucas,
birthmarks, skin cancer, ingrown nails and boils.
The skin is an extremely versatile barrier that shouldn’t be taken
for granted.
We need it to survive. All in all, skin is a wonderful and complex
organ.
Completed by 5th and 6th class 2013/2014