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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
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.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
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.
The human body produces and destroys 15 million blood cells every second.