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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Adolescents often feel clumsy during puberty because during this time of development, their hands and feet grow faster than their arms and legs do. The body is therefore out of proportion. One out of five adolescents actually experiences growing pains during this period.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
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.