Skin - Physical Protection

The skin provides a watertight physical barrier that protects us from injury, infection and dehydration. In the presence of ultraviolet light, skin cells also produce vitamin D, which helps in calcium absorption and maintaining strong bones.

The skin is rich in blood vessels that constrict to conserve heat when the temperature is cold. These blood vessels will enlarge and increase blood flow to release body heat when the temperature is hot. Sweat glands within the skin will also release secretions, called perspiration, in response to heat. Sweat quickly evaporates to create a cooling effect.

Skin is made up of an outer layer of tightly packed cells called the epidermis and an inner layer of connective tissue with nerves and blood vessels called the dermis.

The epidermis has many layers of cells that are constantly being replaced. Within the epidermis, pigmented cells known as melanocytes release varied amounts of melanin. Skin pores on the surface of the epidermis are openings to sweat glands. These pores are most numerous in the palms of the hands and in the armpits.

The epidermis of our skin grows throughout our lifetime. Epidermal cells live for about two weeks. The outer layer of dead epidermal cells is sloughed off and replaced by an inner layer of growing cells. If injured, the epidermis can grow back to repair the damage, such as when someone suffers from a cut.

The dermis is the underlying layer of the skin that provides the blood supply and contains the nerves that give us our sense of touch. The dermis also contains sweat glands, hair follicles and oil glands.

Cells of the epidermis are susceptible to the challenges of our environment, including the potentially damaging rays of the Sun. Melanoma is a type of skin cancer that can develop from overexposure to ultraviolet rays. The chance of developing melanoma can be reduced through the use of high SPF lotions and protective clothing.

Your skin is important for your survival. It protects you from your environment, which is full of potentially dangerous bacteria, viruses and fungal organisms. People suffering from serious burns often lose a layer of skin. These burn victims are at significant risk for infection and death until healed due to the loss of this all-important physical barrier.