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After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
The human body produces and destroys 15 million blood cells every second.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.