The Integumentary System has the largest organ in the human body, which is
the skin. It also consists of hair and fingernails. The skin, however, is the most
important of these. The skin protects and cushions the body’s delicate organs. It
also provides the body with a physical barrier to keep out outside materials and to
keep the body from drying out. The skin also helps our bodies to maintain our body
temperature.

....The skin is made of three separate layers, each with its own particular function.
The three layers are: the epidermis, the dermis, and the subcutaneous layer. The
epidermis is the outermost layer of the skin. It consists of four separate layers of
the epithelial tissue. The outermost layer of the epidermis is called the stratum
corneum. It is around 20-30 cells thick. The cells here are completely changed into
another form and dead, and this what gives the skin its waterproof feeling. The next
two layers are the stratum granulosum and the stratum lucidum. The cell here is not
fully changed yet, but as the growth of the skin pushes them outward, they will move
towards being fully changed. The deepest layer of the epidermis is the stratum
germinativum. The cells here are "mitotical"—that is, they are alive and reproducing.
This is where the growth of the skin takes place.

....The dermis is the second layer of skin, directly under the epidermis. Unlike the
epidermis, the dermis has its own blood supply. Because of the existence of this blood
supply, more difficult structures are able to exist here. Sweat glands are there to
collect water and get rid of wastes from the bloodstream, and take them through
pores in the epidermis. The dermis is also the site of hair roots, and it is here
where the growth of hair takes place. By the time hair reaches outside of the skin,
it is completely dead. The dermis also contains dense joined tissue, made of collagen
and protein fibers, which gives the skin much of its elasticity and strength.

....The next and last layer is the subcutaneous layer. The most important structures
here are the large groupings of adipose tissue, which are used for the storage of fat
tissue. The main function of the subcutaneous layer is to provide a cushion for the
delicate organs lying under the skin. It also functions to coat the body to maintain
body temperature.

....We have special cells known as melanocytes in our skin which produce Melanin,
Melanin is a chemical that gives us our skin color. Melanin in our skin helps to protect
us from harmful UV (ultraviolet) rays from the sun.             

Video Clips: 1. What causes (skin) acne?
,,,,,,,,,,,,,,,,,2. What causes hair to grow?

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