A person will develop wrinkles in his skin when the fat and other soft parts below the top layer of skin are absorbed into the body and the surface itself does not shrink at the same rate. This usually happens when a person reaches late middle age. A blackhead will form on the skin when a hard fatty material from an oil gland blocks the gland'sopening. Skin is a person's largest organ. If it could be spread out flat, an adult's skin would cover about 18 square feet. It weighs about six pounds. The skin is an organ because it performs many important functions including the regulation of the body's temperature and the giving off perspiration.A piece of skin about the size of a quarter will contain one yard of blood vessels, four yards of nerves, 25 nerve endings, 100 sweat glands and more than 3 million cells. An adult has a total of about 2 million sweat glands distributed over the body's surface.
Basically, the skin is made up of two layers: the epidermis, which is the top layer, and the dermis, an inner layer
The epidermis is made up of many cells that are placed next to each other, like bricks on a path. There are between 12 and 15 rows of these cells, arranged one above the other. The cells of the skin grow from the bottom up.
The lowest row has cells that are shaped like posts and they are perpendicular to the cells of the under skin. Above this lowest row of epidermis cells are several rows of round cells which grow flatter and flatter toward the surface of the skin.
The upper layers of the epidermis become drier as they are pushed upward and outward by the new cells below them. When they finally reach the surface, they are shed as thin flakes. These flakes are the dead skin a person often rubs off witha towel after a shower.
The dermis is made up of a closely woven network of connective tissue. It is thickest on a person's back about an eighth of an inch and thinnest on a person's eyelids ¬about a sixteenth of an inch.
There are no blood vessels in the epidermis. In the dermis are blood vessels, vessels for carrying lymph, nerves, glands and hair follicles.
The amount of blood that flows through the skin varies. If the body needs to give off heat, the blood vessels in the skin expand and place the blood closer to the outside air. When the body needs to conserve heat, the blood vessels in the skin tend to contract and thus slow the rate of heat loss from the body.