From your plica semilunaris to Darwin’s tubercle – the 10 ‘pointless’ body parts you never knew existed
THERE are 78 organs in the human body, and hundreds more parts if you count individual bones, muscles and glands.
While we rely on many of them to stay alive - think heart, brain and lungs - scientists now consider some utterly pointless.
Officially called "vestigial", these body parts have become more-or-less functionless in the course of evolution.
They may once have helped protect our ancestors, but now, they are pretty much just extra weight.
You'll likely have heard of the ones most often removed or talked about - like wisdom teeth and male nipples.
But here are 10 "spare parts" you probably never knew existed.
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1. Plica semilunaris
All humans have a plica semilunaris, also known as a third eyelid or nictitating membrane.
But this tiny fold of tissue next to the tear duct in the corner of your eye is actually pretty pointless.
It once covered the whole eyeball and gave our ancestors extra protection - a bit like birds, reptiles and some mammals have a kind of moistening translucent film over their eyes.
Now, it's just a little flap of skin that doesn't really need to be there.
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2. Palmaris longus
The palmaris longus is another body part scientists believe we can do without.
It's so useless in fact, 15 per cent of humans alive today don't actually have one.
shows this forearm muscle doesn't provide any additional arm, grip or pinch strength.
You can check if you have a palmaris longus by holding your arm out and touching your thumb to your pinky.
If you see a raised tendon in the middle of your wrist, you've got one!
3. Darwin's tubercle
Many people have a tiny bump or rounded piece of skin on the top of their ears, officially called Darwin's tubercle.
Some hang jewellery from it after getting it pierced, but that's about all it's good for.
It appears to be more common in certain countries, including and .
This lobule got its name after Charles Darwin mentioned it in his book The Descent of Man.
4. Auriculares
Another part of the ear that we don't really need is a group of muscles called the auriculares.
Historically, these might have been useful in animals like monkeys and cats that need to move their ears to hear well enough.
But in humans, we get by just fine with ours stuck to the side of our heads.
Most people don't use these muscles at all, but some lucky folk can wiggle them on command - though this is really just a party trick.
5. Arrector pili
You could argue this one isn't strictly "useless" as it does have a function, but scientists agree it's not essential in today's world.
The arrector pili is a tiny muscle connected to each hair follicle and the skin.
When it contracts, hairs stand erect and "goosebumps" form on the skin.
This is the body's way of trying to preserve heat when it feels cold.
However, we have a lot less hair on our bodies than our thick-furred ancestors, so it provides very little real insulation.
6. Pyramidalis
The paired pyramidalis are small triangular muscles that lie near the top layer of your abdominal muscles.
Not everyone has them (about 80 of people) and they are only really visible in people with six-packs (think of it as the vertical line in the middle of some people's abs).
Some studies have linked pyramidalis to penis erections or upright posture, but their defined function is "vague".
7. Vomeronasal organ
Ever heard of the vomeronasal organ? Chances are, probably not.
Many people live without one entirely (exactly how many is unclear), but some still have the remnants of it poking through the roof of their nose.
Also called Jacobson's organ, it's present in many mammals, reptiles and amphibians and plays a role in social and sexual behaviour thanks to its pheromone receptor cells and stimulating effect on the secretion of gonadotropic-releasing hormone, according to a review in .
But evidence suggests it is nonfunctional in the humans who carry it, (Third Edition) says.
8. Adenoids
Sitting just past the tonsils where the throat meets the nasal cavity are the adenoids.
While they help children develop immune systems and aid adults in fighting infections, doctors agree they can be removed without dire consequences as they are small or almost non-existent by adulthood.
Swollen adenoids can lead to chronic sinus infections and worsening allergies.
9. Thymus gland
Another body part often said to have no purpose is the thymus gland.
It sits behind your sternum and plays an important role in immune system development in foetuses and newborns - but adults can live well with out it, according to .
10. Fabella
And finally - the fabella.
The small bone is buried in a tendon behind the knee and acted as a kneecap in Old World monkeys.
It was believed to be lost to human evolution, but experts say it's made a resurgence over the last century and it is now three times more common than 100 years ago.
It could also be behind osteoarthritis of the knee - a painful joint condition that gets worse over time, a study published in the Journal of Anatomy suggests.
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Some experts now say the fabella should be routinely removed if found.
Seemingly useless body parts you probably already know about include wisdom teeth, body hair, male nipples and the coccyx.