Your skin works hard. Not only is it the largest organ in the body, but it defends against disease and infection, regulates your temperature and aids in vitamin production.
Even at its thickest point, our skin is only a few millimeters thick. But it is still our heaviest and largest organ, making up about one-seventh of our body weight: Depending on your height and body mass, it weighs between 3.5 and 10 kilograms (7.5 and 22 pounds) and has a surface area of 1.5 to 2 square meters. This goes to show how important skin is for your body and metabolism.
The skin has a lot of different functions. It is a stable but flexible outer covering that acts as a barrier, protecting your body from harmful things in the outside world such as moisture, the cold and sun rays, as well as germs and toxic substances.
Just looking at someone's skin can already tell you a lot – for instance, about their age and health. Changes in skin color or structure can be a sign of a medical condition. For example, people with too few red blood cells in their blood may look pale, and people who have hepatitis have yellowish skin.
Skin also plays an important role in regulating your body temperature. It helps prevent dehydration and protects you from the negative effects of too much heat or cold. And it allows your body to feel sensations such as warmth, cold, pressure, itching, and pain. Some of these sensations trigger a reflex, like automatically pulling your hand back if you accidentally touch a hot stove.
Skin also functions as a large storeroom for the body: The deepest layer of skin can store water, fat and metabolic products. And it produces hormones that are important for the whole body.
If the skin is injured, the blood supply to the skin increases in order to deliver various substances to the wound so it is better protected from infections and can heal faster. Later on, new cells are produced to form new skin and blood vessels. Depending on how deep the wound is, it heals with or without a scar.
To be able to do all of these things, skin consists of three different layers: the outer layer (epidermis), the middle layer (dermis), and the deepest layer (subcutis). Depending on where it is on your body and the demands made on it, your skin varies in thickness. The thickness of your skin depends on your age and sex too: Older people generally have thinner skin than younger people do, and men generally have thicker skin than women do.