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Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
There are more nerve cells in one human brain than there are stars in the Milky Way.
Hypertension is a silent killer because it is deadly and has no significant early symptoms. The danger from hypertension is the extra load on the heart, which can lead to hypertensive heart disease and kidney damage. This occurs without any major symptoms until the high blood pressure becomes extreme. Regular blood pressure checks are an important method of catching hypertension before it can kill you.
The familiar sounds of your heart are made by the heart's valves as they open and close.
In 1835 it was discovered that a disease of silkworms known as muscardine could be transferred from one silkworm to another, and was caused by a fungus.