Why Do People Grow Old?

Aging is a result of the gradual failure of the body’s cells and organs to replace or repair themselves. This is because there is a limit to the number of times that each cell can divide. As the body’s cells begin to near this limit, the rate at which they divide slows down. Sometimes the new cells that are produced have defects or do not carry out their usual task effectively. Organs can then begin to fail, tissues change in structure, and the chemical reactions that power the body become less efficient.

Elderly people are no longer growing, and so they are not as active as they used to be. For this reason, they do not need to eat as much, and quite often become thinner. The body loses muscles as well as fat, and sometimes older people become unsteady on their feet.

Why Do I Have Nails?

Human need nails to provide a firm support for the sensitive skin on the fingertips. If you cut your fingernails too short you will notice how difficult it is to pick up small objects. Nails grow continuously from an area called the nail bed, or quick. Because your nails are transparent, you can see right into the tissue below the nail, which is always pink because it contains blood. Nails grow at a rate of about 0.1 mm per day. They are made of Keratin, the same material as hair. Because nails are not living material, they do not hurt when you cut them.

Your fingertips are covered with tiny ridges that are caused by patterns in the deeper layers of skin. These ridges probably give a better grip when you pick things up. As long ago as 1823 it was realized that each person’s fingerprint is unique, and fingerprints are how widely used for identification of criminal and sometimes as personal identification. Many hospitals take a footprint from newborn babies. Because feet carry similar identifying patterns. This is a good form of identification.

How Does the Body Keep At Proper Temperature

The body has several systems to keep itself at the right temperature. Heat is produced by the breakdown of food substances stored in the body. The chemical reactions in the body will only take place properly if the body is kept at the ideal temperature, so any extra heat has to be removed. Heat leaves the body through the lungs, as you breathe out warmed air, and also through the skin. If you are very hot, the blood vessels near the skin’s surface open wider to increase the blood flow, so you look a bit pink. The extra blood means more heat leaves the skin surface, cooling your body.

Vigorous exercise means the body needs to generate extra energy. Some of this is produced as heat. Excess heat is removed by sweating. Sweating removes excess salt and wastes through the skin. It also helps to keep you cool because sweat takes heat away from the body as it evaporates on the skin. If you have been exercising and are very sweaty, and then stand in a draft, you will notice this cooling effect very quickly. Sweat is a watery liquid, but other skin glands release an oily substance called sebum that helps to lubricate the skin and keep it supple.