How come you wake up at night to urinate but not to do anything else?
We’re often too embarrassed to inquire about the strange facts of our internal plumbing, but the answer is just plain biology. The sophisticated, intelligent neurons in your gut that control colon contractions, which push out waste, are also influenced by your body’s circadian rhythm, the internal clock that wakes you when it’s light out and makes you feel sleepy at night. So most people don’t have the urge to empty their colon in the middle of the night. On the other hand, the bladder, which acts a reservoir for the continuous flow of urine produced in the kidneys, can stretch only up to a certain volume before you gotta go. Normally, you can sleep six to eight hours without having to urinate, but certain medical conditions or drinking too much water before bed can wake you to use the bathroom at night.—Pankaj J. Pasricha, MD, director of neurogastroenterology at Johns Hopkins Center for Neurogastroenterology
Why do we have fingerprints?
Many experts think it’s to improve grip, but a British study from a few years back suggests otherwise. Researchers found that a fingerprint’s ridges actually made it harder to hold flat, smooth surfaces, like Plexiglas, because they reduced the skin’s contact area. Instead, they think our prints might help wick water off our fingertips or allow our skin to stretch more easily, which can protect it from damage and help prevent blisters. Other scientists have suggested fingerprints could improve our sense of touch. What we do know for sure is that no two people’s fingerprints are the same, even among identical twins.—V. Patteson Lombardi, PhD, research assistant professor of biology at the University of Oregon Check out these nine other body parts are as unique as your fingerprints, too.
Can achy joints really forecast the weather?
Maybe. A change in barometric readings may be part of the reason why weather can predict our health: Atmospheric pressure often drops right before bad weather sets in; this shift could cause body tissue to expand, which can lead to swelling and pain. The effect is slight, but people who have arthritic or inflamed joints may detect the difference. Temperature may have an impact too: In 2007, researchers at Tufts University found that every ten-degree drop in temperature corresponded with a small increase in osteoarthritic knee pain.—Leon Benson, MD, orthopedic surgeon at the Illinois Bone and Joint Institute and spokesperson for the American Academy of Orthopaedic Surgeons