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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.
Looking at the sun may not only cause headache and distort your vision temporarily, but it can also cause permanent eye damage. Any exposure to sunlight adds to the cumulative effects of ultraviolet (UV) radiation on your eyes. UV exposure has been linked to eye disorders such as macular degeneration, solar retinitis, and corneal dystrophies.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
It is widely believed that giving a daily oral dose of aspirin to heart attack patients improves their chances of survival because the aspirin blocks the formation of new blood clots.
![The pancreas. This organ sits just below the stomach and is both an exocrine and an endocrine gland.](https://biology-forums.com/gallery/47/medium_14755_28_08_12_1_42_25_8233102.jpeg)
![The anterior pituitary is sometimes called the master gland because it secretes many hormones that r](https://biology-forums.com/gallery/47/medium_14755_28_08_12_1_42_27_82371656.jpeg)