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12 Underappreciated (But Equally Precious) Bodily Fluids

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Blood, sweat, tears? Classic bodily fluids. And then there’s mucus, spit, semen, and urine—well known to juvenile minds everywhere. But blood, for instance, only makes up 9% of your total bodily fluid. What else is oozing around inside you?

1. Interstitial Fluid

Interstitial Fluid, AKA tissue fluid, works in conjunction with lymph and plasma (the liquid part of your blood) to maintain your body’s internal pressure and make sure your organs and other fluids properly interact. Most interstitial fluids have a specific job and a specific name, like peritoneal fluid, which lubricates everything inside the abdomen, or pleural fluid, which coats the lungs to allow them to do that whole oxygen exchange thing so you can live. And you were giving air all the credit.

2. Lymph

Lymph is pale and doesn’t look like much, but it plays a huge role in keeping you from dying. Several roles, in fact. It runs throughout your entire body, identifies bacteria and viruses, carries them to your lymph nodes to activate the immune system, then meets up with your blood stream to deliver important items like proteins and infection-fighting white blood cells. It delivers fats from your digestive system to wherever your body needs them (fatty lymph is called chyle), and toxins to the excretory system for disposal. And all the while it helps interstitial fluid maintain that fluid balance. Imbalanced fluids result in swelling, like in the ankles of pregnant ladies.

3. Serum

If plasma is blood without the red blood cells, serum is plasma without the clotting agents like fibrin and platelets. Of its many roles, it’s best known as “the stuff inside a blister.” Blood and lymph both contain serum, but all three exist separately in the body, and serve different purposes at different times. But serum is the most basic of the three, which kind of explains its all-purpose, old-timey name.

4. Aqueous and Vitreous Humors

And speaking of old-timey names—yes, you have humors. But these aren’t the “black,” “yellow,” “phlegm” and “blood” humors, the imbalance of which ancient docs claimed were the source of all malady. These fluids are humors in name only, and are necessary to eye function: The aqueous humor is a clear fluid that brings nutrients to the lens area of your eye, so that you’re not—you know—looking at blood all the time. The vitreous humor (or vitreous body) is the gelatinous goop that fills the inside of your eyeball.

5. Bile

Bile is another term misused by physicians of yesteryear—the black and yellow humors were called “yellow bile” and “black bile,” too much of which would make a person overly idealistic or melancholy, respectively. Real bile, or gall, is produced by the liver, held in the gallbladder (Greco-Romans were right about that part) and it squirts into the beginning of the small intestine when you eat. Its salts act kind of like soap, breaking down fats into more absorbable/digestible bits. Along with urine, bile helps the body excrete most of its toxins and other undesirables.

6. Cerebrospinal fluid

Cerebrospinal fluid—or CSF to the cool kids in the know—surrounds the spinal cord and brain, and fills the hollow spaces all up inside them. Not only does it cushion your all-important central nervous system from potential trauma, it also removes cell waste, and delivers hormones that help the brain and spinal cord communicate with the rest of the body.

7. Endolymph

Endolymph is not really lymph in the aforementioned sense. It’s the fluid in your inner ear that helps you keep your balance. Like the bubble in a level, your endolymph holds its place in relation to gravity, while your body moves. Small hairs in the ear detect the position of the endolymph, and tell the brain how best to maintain your equilibrium, so you don’t wind up hurling that...other...bodily fluid.

8. Sebum

Sebum is a fancy word for skin oil—that stuff you have way too much of when you’re going through puberty. Secreted by sebaceous glands, sebum is odorless, but can collect zit-causing bacteria, which stinks as it decomposes.

9. Milk

Milk only occurs in some humans of course, but the mammary glands that produce it are similar to other glands in the body. Scientists believe they probably evolved from either sweat glands or the aforementioned sebaceous glands. What you’ve heard is true: Men have the right hardware for lactation, and if the necessary hormones happen to be present, they, too, can nurse their young.

10. Female Ejaculate

Female Ejaculate is another lady secretion that has the scientific community pretty baffled. Studies strongly suggest that the fluid most closely resembles prostate plasma, and may originate in lady glands analogous to the male prostate.

11. Cytosol

Cytosol, or intracellular fluid, is the fluid inside a given cell—unlike all the other fluids we’ve mentioned here, which work outside and around cells. Remember those cell cross-sections you had to draw in middle school biology? Cytosol is the gunk in which all the other parts of the cell are suspended. You may never lay eyes on your intracellular fluid, but it makes up a whole third of your total fluid volume.

12. Cerumen

Cerumen is just the fancy name for earwax, a combination of sebaceous and modified sweat-like secretions that protect the ear canal from potentially harmful foreign bodies. There are actually two kinds of earwax: the brown, sticky “wet” kind, and the grey, flaky “dry” kind. Turns out there's a genetic difference between the two, identifiable in a single DNA base pair. Wet-type cerumen is the dominant type, more common in people of European and African heritage. Dry-type cerumen is recessive, and more common in people of Asian and Native American decent. Tracing the earwax gene has recently given researchers a window into the history of human distribution.

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Echo Bridge Home Entertainment
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15 Must-See Holiday Horror Movies
Echo Bridge Home Entertainment
Echo Bridge Home Entertainment

Families often use the holidays as an excuse to indulge in repeat viewings of Planes, Trains and Automobiles and Elf. But for a certain section of the population, the yuletide is all about horror. Although it didn’t truly emerge until the mid-1970s, “holiday horror” is a thriving subgenre that often combines comedy to tell stories of demented Saint Nicks and lethal gingerbread men. If you’ve never seen Santa slash someone, here are 15 movies to get you started.

1. THANKSKILLING (2009)

Most holiday horror movies concern Christmas, so ThanksKilling is a bit of an anomaly. Another reason it’s an anomaly? It opens in 1621, with an axe-wielding turkey murdering a topless pilgrim woman. The movie continues on to the present-day, where a group of college friends are terrorized by that same demon bird during Thanksgiving break. It’s pretty schlocky, but if Turkey Day-themed terror is your bag, make sure to check out the sequel: ThanksKilling 3. (No one really knows what happened to ThanksKilling 2.)

2. BLACK CHRISTMAS (1974)

Fittingly, the same man who brought us A Christmas Story also brought us its twisted cousin. Before Bob Clark co-wrote and directed the 1983 saga of Ralphie Parker, he helmed Black Christmas. It concerns a group of sorority sisters who are systematically picked off by a man who keeps making threatening phone calls to their house. Oh, and it all happens during the holidays. Black Christmas is often considered the godfather of holiday horror, but it was also pretty early on the slasher scene, too. It opened the same year as The Texas Chainsaw Massacre and beat Halloween by a full four years.

3. SILENT NIGHT, DEADLY NIGHT (1984)

This movie isn’t about Santa Claus himself going berserk and slaughtering a bunch of people. But it is about a troubled teen who does just that in a Santa suit. Billy Chapman starts Silent Night, Deadly Night as a happy little kid, only to witness a man dressed as St. Nick murder his parents in cold blood. Years later, after he has grown up and gotten a job at a toy store, he conducts a killing spree in his own red-and-white suit. The PTA and plenty of critics condemned the film for demonizing a kiddie icon, but it turned into a bona fide franchise with four sequels and a 2012 remake.

4. RARE EXPORTS: A CHRISTMAS TALE (2010)

This Finnish flick dismantles Santa lore in truly bizarre fashion, and it’s not easy to explain in a quick plot summary. But Rare Exports involves a small community living at the base of Korvatunturi mountain, a major excavation project, a bunch of dead reindeer, and a creepy old naked dude who may or may not be Santa Claus. Thanks to its snowy backdrop, the movie scored some comparisons to The Thing, but the hero here isn’t some Kurt Russell clone with equally feathered hair. It’s a bunch of earnest kids and their skeptical dads, who all want to survive the holidays in one piece.

5. TO ALL A GOODNIGHT (1980)

To All a Goodnight follows a by-now familiar recipe: Add a bunch of young women to one psycho dressed as Santa Claus and you get a healthy dose of murder and this 1980 slasher flick. Only this one takes place at a finishing school. So it’s fancier.

6. KRAMPUS (2015)

Although many Americans are blissfully unaware of him, Krampus has terrorized German-speaking kids for centuries. According to folklore, he’s a yuletide demon who punishes naughty children. (He’s also part-goat.) That’s some solid horror movie material, so naturally Krampus earned his own feature film. In the movie, he’s summoned because a large suburban family loses its Christmas cheer. That family has an Austrian grandma who had encounters with Krampus as a kid, so he returns to punish her descendants. He also animates one truly awful Jack-in-the-Box.

7. THE GINGERDEAD MAN (2005)

“Eat me, you punk b*tch!” That’s one of the many corny catchphrases spouted by the Gingerdead Man, an evil cookie possessed by the spirit of a convicted killer (played by Gary Busey). The lesson here, obviously, is to never bake.

8. JACK FROST (1997)

No, this isn’t the Michael Keaton snowman movie. It’s actually a holiday horror movie that beat that family film by a year. In this version, Jack Frost is a serial killer on death row who escapes prison and then, through a freak accident, becomes a snowman. He embarks on a murder spree that’s often played for laughs—for instance, the cops threaten him with hairdryers. But the comedy is pretty questionable in the infamous, and quite controversial, Shannon Elizabeth shower scene.

9. ELVES (1989)

Based on the tagline—“They’re not working for Santa anymore”—you’d assume this is your standard evil elves movie. But Elves weaves Nazis, bathtub electrocutions, and a solitary, super grotesque elf into its utterly absurd plot. Watch at your own risk.

10. SINT (2010)

The Dutch have their own take on Santa, and his name is Sinterklaas. Sinterklaas travels to the Netherlands via steamship each year with his racist sidekick Zwarte Piet. But otherwise, he’s pretty similar to Santa. And if Santa can be evil, so can Sinterklaas. According to the backstory in Sint (or Saint), the townspeople burned their malevolent bishop alive on December 5, 1492. But Sinterklaas returns from the grave on that date whenever there’s a full moon to continue dropping bodies. In keeping with his olden origins, he rides around on a white horse wielding a golden staff … that he can use to murder you.

11. SANTA’S SLAY (2005)

Ever wonder where Santa came from? This horror-comedy claims he comes from the worst possible person: Satan. The devil’s kid lost a bet many years ago and had to pretend to be a jolly gift-giver. But now the terms of the bet are up and he’s out to act like a true demon. That includes killing Fran Drescher and James Caan, obviously.

12. ALL THROUGH THE HOUSE (2015)

Another Santa slasher is on the loose in All Through the House, but the big mystery here is who it is. This villain dons a mask during his/her streak through suburbia—and, as the genre dictates, offs a bunch of promiscuous young couples along the way. The riddle is all tied up in the disappearance of a little girl, who vanished several years earlier.

13. CHRISTMAS EVIL (1980)

Several years before Silent Night, Deadly Night garnered protests for its anti-Kringle stance, Christmas Evil put a radicalized Santa at the center of its story. The movie’s protagonist, Harry Stadling, first starts to get weird thoughts in his head as a kid when he sees “Santa” (really his dad in the costume) groping his mom. Then, he becomes unhealthily obsessed with the holiday season, deludes himself into thinking he’s Santa, and goes on a rampage. The movie is mostly notable for its superfan John Waters, who lent commentary to the DVD and gave Christmas Evil some serious cult cred.

14. SANTA CLAWS (1996)

If you thought this was the holiday version of Pet Sematary, guess again. The culprit here isn’t a demon cat in a Santa hat, but a creepy next-door neighbor. Santa Claws stars B-movie icon Debbie Rochon as Raven Quinn, an actress going through a divorce right in the middle of the holidays. She needs some help caring for her two girls, so she seeks out Wayne, her neighbor who has an obsessive crush on her. He eventually snaps and dresses up as Santa Claus in a ski mask. Mayhem ensues.

15. NEW YEAR’S EVIL (1980)

Because the holidays aren’t over until everyone’s sung “Auld Lang Syne,” we can’t count out New Year’s Eve horror. In New Year’s Evil, lady rocker Blaze is hosting a live NYE show. Everything is going well, until a man calls in promising to kill at midnight. The cops write it off as a prank call, but soon, Blaze’s friends start dropping like flies. Just to tie it all together, the mysterious murderer refers to himself as … “EVIL.”

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The American Museum of Natural History
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10 Surprising Ways Senses Shape Perception
The American Museum of Natural History
The American Museum of Natural History

Every bit of information we know about the world we gathered with one of our five senses. But even with perfect pitch or 20/20 vision, our perceptions don’t always reflect an accurate picture of our surroundings. Our brain is constantly filling in gaps and taking shortcuts, which can result in some pretty wild illusions.

That’s the subject of “Our Senses: An Immersive Experience,” a new exhibition at the American Museum of Natural History in New York City. Mental Floss recently took a tour of the sensory funhouse to learn more about how the brain and the senses interact.

1. LIGHTING REVEALS HIDDEN IMAGES.

Woman and child looking at pictures on a wall

Under normal lighting, the walls of the first room of “Our Senses” look like abstract art. But when the lights change color, hidden illustrations are revealed. The three lights—blue, red, and green—used in the room activate the three cone cells in our eyes, and each color highlights a different set of animal illustrations, giving the viewers the impression of switching between three separate rooms while standing still.

2. CERTAIN SOUNDS TAKE PRIORITY ...

We can “hear” many different sounds at once, but we can only listen to a couple at a time. The AMNH exhibit demonstrates this with an audio collage of competing recordings. Our ears automatically pick out noises we’re conditioned to react to, like an ambulance siren or a baby’s cry. Other sounds, like individual voices and musical instruments, require more effort to detect.

3. ... AS DO CERTAIN IMAGES.

When looking at a painting, most people’s eyes are drawn to the same spots. The first things we look for in an image are human faces. So after staring at an artwork for five seconds, you may be able to say how many people are in it and what they look like, but would likely come up short when asked to list the inanimate object in the scene.

4. PAST IMAGES AFFECT PRESENT PERCEPTION.

Our senses often are more suggestible than we would like. Check out the video above. After seeing the first sequence of animal drawings, do you see a rat or a man’s face in the last image? The answer is likely a rat. Now watch the next round—after being shown pictures of faces, you might see a man’s face instead even though the final image hasn’t changed.

5. COLOR INFLUENCES TASTE ...

Every cooking show you’ve watched is right—presentation really is important. One look at something can dictate your expectations for how it should taste. Researchers have found that we perceive red food and drinks to taste sweeter and green food and drinks to taste less sweet regardless of chemical composition. Even the color of the cup we drink from can influence our perception of taste.

6. ... AND SO DOES SOUND

Sight isn’t the only sense that plays a part in how we taste. According to one study, listening to crunching noises while snacking on chips makes them taste fresher. Remember that trick before tossing out a bag of stale junk food.

7. BEING HYPER-FOCUSED HAS DRAWBACKS.

Have you ever been so focused on something that the world around you seemed to disappear? If you can’t recall the feeling, watch the video above. The instructions say to keep track of every time a ball is passed. If you’re totally absorbed, you may not notice anything peculiar, but watch it a second time without paying attention to anything in particular and you’ll see a person in a gorilla suit walk into the middle of the screen. The phenomenon that allows us to tune out big details like this is called selective attention. If you devote all your mental energy to one task, your brain puts up blinders that block out irrelevant information without you realizing it.

8. THINGS GET WEIRD WHEN SENSES CONTRADICT EACH OTHER.

Girl standing in optical illusion room.

The most mind-bending room in the "Our Senses" exhibit is practically empty. The illusion comes from the black grid pattern painted onto the white wall in such a way that straight planes appear to curve. The shapes tell our eyes we’re walking on uneven ground while our inner ear tells us the floor is stable. It’s like getting seasick in reverse: This conflicting sensory information can make us feel dizzy and even nauseous.

9. WE SEE SHADOWS THAT AREN’T THERE.

If our brains didn’t know how to adjust for lighting, we’d see every shadow as part of the object it falls on. But we can recognize that the half of a street that’s covered in shade isn’t actually darker in color than the half that sits in the sun. It’s a pretty useful adaptation—except when it’s hijacked for optical illusions. Look at the image above: The squares marked A and B are actually the same shade of gray. Because the pillar appears to cast a shadow over square B, our brain assumes it’s really lighter in color than what we’re shown.

10. WE SEE FACES EVERYWHERE.

The human brain is really good at recognizing human faces—so good it can make us see things that aren’t there. This is apparent in the Einstein hollow head illusion. When looking at the mold of Albert Einstein’s face straight on, the features appear to pop out rather than sink in. Our brain knows we’re looking at something similar to a human face, and it knows what human faces are shaped like, so it automatically corrects the image that it’s given.

All images courtesy of the American Museum of Natural History unless otherwise noted.

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