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The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
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.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
In the United States, an estimated 50 million unnecessary antibiotics are prescribed for viral respiratory infections.