If you want to find out whether people smoke -- without sniffing their breath or clothing -- take a look at their fingernails. One of the telltale signs of smoking is that it turns the fingernails an ugly yellowish-brown color, especially on the hand that holds the cigarette.
The fingers aren't the only place where you can notice the effects of smoking on the skin, however. Smoking can also affect skin on other parts of the body, especially the face, and it can increase your chances of getting some types of skin diseases. It is well known that smokers tend to get wrinkles more severely and at a younger age than nonsmokers. While smoking has specific negative effects on many parts of the body -- including the skin -- there are some diseases, such as the skin condition acne, that have a questionable association or have not been causally linked to smoking.
definition
What does skin do?
The skin is the largest organ in the body. The skin, in conjunction with hair and nails, make up the integumentary system whose primary function is to protect the body from the outside world. Other functions of the skin are to retain body fluids, eliminate waste, regulate body temperature and protect against disease. The skin provides the removal of dead cells and sweat, both of which contain waste products.
The skin is composed of two main layers called the epidermis and the dermis. The outermost layer of the skin, the epidermis, is comprised of mostly dead cells. The epidermis contains keratin, a fibrous protein, which forms the basic structure of hair, nails, and calluses. The epidermis also contains cells called melanocytes, which produce a brown pigment called melanin. Melanin can absorb ultraviolet radiation and thereby protect the rest of your cells from the sun's radiation.
The dermis is the innermost later of the skin, and, unlike the epidermis, it is composed of living cells. The dermis contains nerve endings, blood vessels, glands, smooth muscles, hair follicles, and sense organs. The primary function of the dermis is to help control our body temperature. For instance, when it is cold outside the blood vessels in the dermis become narrow because the body needs to conserve heat, whereas on a hot day the blood vessels widen, increasing heat loss. The two major types of glands in the dermis are sweat glands and sebaceous (oil) glands. The sweat glands produce sweat (watery secretions), which contains salt, water, and other compounds. The act of sweating helps cool the body, an example of how the skin is essential in regulating body temperature.
Why is the skin important?
As the body's primary protector, the skin has multiple roles in homeostasis -- the way in which the body maintains stability -- including temperature regulation, sensory reception, biochemical synthesis, and absorption. In addition, the skin serves as a protective barrier against the entry of viruses and ultra-violet radiation, as well as preventing water loss.
