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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.
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.
Vampire bats have a natural anticoagulant in their saliva that permits continuous bleeding after they painlessly open a wound with their incisors. This capillary blood does not cause any significant blood loss to their victims.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
In most cases, kidneys can recover from almost complete loss of function, such as in acute kidney (renal) failure.