Facts about the skeleton

Facts about the skin

Facts about eyes

Facts about hair and nails

The only parts of the human body that are hairless are the palms of the hands and soles of the feet, undersides of the fingers, undersides of the toes, and the lips. "Goose pimples" are caused by tiny muscle cells at the base of hair follicles. These muscles contract when you are very cold or frightened and you can see them then as little bumps or "goose pimples." When they contract, the hair also straightens up.

If you completely remove a nail without injuring the root, it will take five to six months before the nail has grown back completely, because a nail grows very slowly. It takes three to four weeks for a nail to grow out from the root until it becomes visible above the cuticle.

Blinking is a reflex action and each person has his own "normal blinking rate." An infant does not blink regularly the first few months of its life. The fluid that covers the eye is mostly tear fluid. By blinking, you actually draw this fluid over the eyes. The tear fluid does not spill over the lids because there is an oily secretion covering the lid edges. You cry tears when a nerve in the eye is stimulated. Sneezing and coughing stimulate this nerve. Emotions also can cause this nerve to be stimulated. Only human beings can cry when they are emotionally upset. Animals cry only when they sneeze or cough. Tiny babies do not cry tears when they are upset until they are about five months old.

The skin can really be called a "mirror of the system." Its texture and color change with changes in bodily health. Emotions are recorded by the skin:

1) when you are embarrassed, your skin may flush and become red;

2) when you are frightened, your skin may become white;

3) anger and laughter wrinkles are recorded on the skin of your face.

Skin stretches when you gain weight and shrinks when you lose weight. It is elastic. As you grow older, you lose your elasticity.

Babies very rarely break a bone, because an infant's bones are still soft. These bones bend very easily under pressure and straighten out when the pressure is gone. As a person grows older, the bones become lighter in weight and more brittle, because calcium in the bones seeps out. That is why an older person may break a bone more easily than a younger one. Do you know why bones tend to "creak" as you become older? The cartilage that covers the ends of the bone, cushioning the area where two bones meet, becomes thinner and sometimes disappears. Now bone meets bone, without a cushion in between and the joint stiffens and cracks.

The 22 bones that make up the skull do not move at all-with the exception of the "mandible" or lower jaw, so that you could eat or talk.

Дата добавления: 2014-12-23