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Before a vaccine is licensed in the USA, the Food and Drug Administration (FDA) reviews it for safety and effectiveness. The CDC then reviews all studies again, as well as the American Academy of Pediatrics and the American Academy of Family Physicians. Every lot of vaccine is tested before administration to the public, and the FDA regularly inspects vaccine manufacturers' facilities.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Atropine was named after the Greek goddess Atropos, the oldest and ugliest of the three sisters known as the Fates, who controlled the destiny of men.