The Largest Organ in Your Body
Did you know that your skin, hair, and the millions of sweat and oil glands make up your largest body system, the integumentary system?
Skin is the largest organ of your body, but you may not know much about it. Only a few millimeters thick in most places, it still has layers of tissue.
Look at the diagram below and find the structures as you read about them.
Image Credit: National Cancer Institute, Don Bliss
The epidermis is the outer layer of cells that forms a protective layer over the inner layer, the dermis. The epidermis prevents excessive water loss and also prevents disease-causing microorganisms from entering through skin.
Melanocytes are cells in the skin that contain melanin. Melanin absorbs light energy and helps protect against the damaging ultraviolet rays from the sun. Melanin give the skin color.
New skin cells are made at the bottom of the epidermis. As older cells are shed from the top of the epidermis, new cells rise to take their places.
The dermis is a much thicker layer that contains muscle tissue, nerve tissue, and blood. This layer also contains fat tissue which helps retain heat. Several other structures are found in this layer, such as hair follicles, oil glands, and sweat glands. Oil glands give off oils which help keep skin and hair soft and relatively waterproof. Sweat glands give off wastes and evaporates water to cool the body. Nerve cells in the dermis receive messages from the environment and sense pain, temperature, and pressure.
Skin Functions
The skin is not just a covering for the body. It performs very important functions for your body:
● Regulates body temperatures
Blood vessels in the skin dilate (get larger) when your body is too hot. This increases blood flow and heat is lost. Sweat glands produce sweat if you are too warm and evaporation of the sweat from your skin lowers your temperature.
● Retains moisture
● Keeps out bacteria and other pathogens (disease-causing organisms).
● Heals injuries to skin layers. When you have an injury to a layer of skin, blood vessels deliver nutrients, chemicals, and cells to the site which help your skin heal the wound. Blood clots form scabs which give the skin underneath time to heal completely. The scab falls off then the damaged tissue is replaced.
When you are too cool, blood vessels constrict (get smaller) and heat is retained. These are major ways that humans maintain a constant, warm-blooded body temperature.
Fast Fact:
Do snakes sweat?
Cold-blooded animals do not maintain a
constant temperature. They would be the
temperature of their environment if they
did not adopt other ways to control their
temperature. For example, reptiles in the
desert find shade during the day and
burrow under leaves to maintain a body
temperature that allows them to survive extreme temperatures.
Skin cancer
When skin cells are damaged from the
ultraviolet rays of the sun, skin cancer can
form. Skin cancer used to occur mostly in
people over age 50. In recent years, there has
been a steady increase in younger people
getting skin cancer. This is most likely because
of the increase in tanning salons and the
practice of tanning all year long. People with fair skin, with red or blond hair, or with blue or light-colored eyes are most at risk.
Protect yourself from too much sun exposure by using sunscreen or sunblock lotions and wearing protective clothing.
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