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The human body produces and destroys 15 million blood cells every second.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
Most strokes are caused when blood clots move to a blood vessel in the brain and block blood flow to that area. Thrombolytic therapy can be used to dissolve the clot quickly. If given within 3 hours of the first stroke symptoms, this therapy can help limit stroke damage and disability.
Vaccines prevent between 2.5 and 4 million deaths every year.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.