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The familiar sounds of your heart are made by the heart's valves as they open and close.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
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.
Blood is approximately twice as thick as water because of the cells and other components found in it.
Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the United States has risen 46% since 1996.