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When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
In most cases, kidneys can recover from almost complete loss of function, such as in acute kidney (renal) failure.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
The human body produces and destroys 15 million blood cells every second.