“Fascinating Bordering On Funny”: 46 Human Body Quirks You Probably Didn’t Know

I'm not a medical person but my mum was a midwife before she retired. She told me about the septum primum and has always referred to it as the most amazing thing about human development that continues to blow her mind.

In short, it's a valve in the heart that develops when in the womb. It allows blood to bypass the lungs, which are too immature and the mother's blood supplies oxygen needs.

What's remarkable is that when the baby is delivered and draws its first breath, the change in pressure in the circulatory system causes the valve to shut, cutting off the blood flow from the mother and allowing oxygenated blood from the lungs to pass through the heart.

I'm not in medicine so may have explained that a little wrong - perhaps someone can correct me.

It takes about 20% more anesthetics to knock out a Redhead then the normal human.

Doctors can scoop out part (even half!) of your brain, and it will simply fill with fluid and the rest of the brain will do its best to compensate.

Source: Have epilepsy, went to seminar on treatment using brain surgery.

You constantly have cancerous cells in your body all the time. The only time it's an issue is when your body can't get rid of the cells.

You can't move your eyes smoothly UNLESS you are tracking an object. If you scan a room your eyes actually move in a jerking motion. But scan the room focusing on a moving finger and your eyes move perfectly smoothly.

The female brain releases chemicals after childbirth that have been shown to dull the memory of the pain.

It's believed that this is an evolutionary response to increased vaginal sensitivity, and without it women would be unwilling to have more than one child as the pain is so great, resulting in the eventual extinction of the human race.

Bones can bleed quite a lot. Femur fractures can cause up to a liter of blood loss by themselves!

Your heart has several back up systems to keep beating on its own. You have a node that operates in a normal heart that keeps its beat. If that fails to fire, another part takes over. If that fails, then another, and another and another. Until the actual heart cells of the ventricles are beating to keep you alive. The hearts pacemaker cells are amazing.

I know a couple of fun ones. When we undergo cellular respiration the waste product is CO2. When we lose weight the extra weight is being breathed out. Plants take that CO2 and can turn it into wood.

Sometimes when people suffer facial injuries the nerves can get crossed when they try to repair themselves. This can result in crying whenever somebody smells something delicious instead of salivating.

The human heart pumps the equivalent volume of the entire blood supply in 60-90 seconds.

Many people with severe coronary disease develop a transverse crease (Frank's sign). This can appear before they even have notable symptoms.

After you eat a large meal, the acid produced in your stomach in effect makes your blood slightly basic. This makes your oxygen bond harder to your red blood cells so less oxygen gets released into your tissues. The effect- tiredness after you eat.

Edit: I should add, now that I'm going back to this, that your blood is always slightly basic at a pH of 7.4. What I meant was that after you eat, your blood becomes more basic than 7.4 after the alkaline tide that eating causes.

The Elderly can experience memory loss from having constipation. They can't remember because they can't poop!

The pterion, commonly called "God's little joke": about halfway between your eye and the top of your year is the thinnest and weakest part of the skull. It's the place where several skull bones meet. Right behind it (interior), there's a super important artery. If it fractures and the artery is perforated, the person can die pretty fast. That's why whenever someone receives a blow to this section, they need immediate attention.

Your body uses weight, nerves, and eyes to determine your spatial orientation. If you suddenly cannot see, typically you're fine because your brain can sense that you've got two feet on the ground, thus it can use the weight on two feet to determine the best way to keep you upright. (and why you become disoriented in a tunnel with spinning lights)

If; however, you lift one leg with your eyes closed, then your body needs to find out a way to know where you're at. So...you'll start feeling the nerves in the ankle that is touching the ground begin to fire in a sort of pattern around your ankle. your body is using a patterned out of balance means to determine where balance is.

also, nothing is real time. there are fractions of a second between when you touch something and when your brain says you've touched it. therefore, even as you type, your fingers are actually touching the keys before your brain is registering it. you're brain is typing in the past but anticipating for the future. Also, doing things that require minutely fine timing (like releasing a baseball) become even more complex because your hand must release the ball at a very precise time to get it to its target. Your brain has to anticipate this tiny amount of lag because you're fingers don't react the instant the brain says let go.

Our system of producing energy involves using oxygen in our cells to essentially break down the glucose we eat into water, carbon dioxide, and ATP (this is why we inhale oxygen in and exhale carbon dioxide out). The ATP is essentially the final result, which is the body's energy currency.

Babies, however, have a certain type of fat called brown fat. In this fat, this process is purposefully not efficient, and a lot of energy produced is given off as heat instead of making ATP.

This is super important, because babies have a large surface area : body ratio, so they give off a lot of heat to the environment. Brown fat helps balance this problem and keeps them warm.

I think something a lot of people don't realise is simply the amount of variation in anatomy between us all. There are lots of examples; for instance, how many of you have the palmaris longus muscle?

The development of your visual pathway in your brain requires stimulation from your vision.

Thus, if one of your eyes doesn't get stimulated, the brain will eventually ignore the signal from that eye you will be blind, even though the eye can appear perfectly normal. This is reversible up until the age of around 5, and eventually becomes permanent if not treated.

This is called ambylopia and can occur from being cross eyed at birth, being born with a cataract, not being able to see up close with one eye, and many other reasons.

Oh god there's so many.

Proprioception: your brain knows where all your various body parts are without you being able to see them. Close your eyes and pinch your eyelash, and you'll see just how precise it is - your brain knows exactly where your hand is, and while you might have to try to find your eyelash, you will almost never actually touch your eyelid, despite not being able to see where your hand is.

Hearing and timing: Your brain picks up on exact locations of sounds based on the time it takes to reach one ear before the other, and the volume difference between the two. Throw something behind you, close your eyes, listen for the sound, and turn towards it without opening your eyes. Then check how close your were to looking directly at the location of the object. Usually, you will be extremely accurate, although practice can improve the accuracy.

Your eyes: You were born with blue eyes, and exposure to ultraviolet radiation from the sun turned them to whatever colour they are now (or didn't, depending on your genetics: blue-eyed people are technically part-albino mutants, with a certain protein "turned off" in their eyes, which stops melanin production, and forces your eyes to stay albino-blue). They use up about 90% of the average person's daily sensory input, and the muscles in them flex and relax so constantly that it would be the leg muscle equivalent of walking about 50 miles a day.

The most interesting, I think, however, is your skin. The interesting part doesn't come from the skin itself, though, it's how dangerous life would be without it. You see, your skin is made of several layers, the top few layers (epidermis) giving it the colour that it needs for optimal survival. The basal layer of the epidermis is technically the only "living" layer (receiving oxygen), producing cells that are basically just nuclei and sacs of melanin, the size and distribution of which give your skin colour. These cells rapidly decompose until the only thing left is a sac of melanin. Here's the cool part, though: your skin is always, always, ALWAYS adjusting the amount and distribution of melanin. Were it not doing that, you would begin to suffer from UV radiation poisoning almost immediately (resulting in widespread burns across the body and general nausea, dizziness, and the other symptoms associated with sun poisoning). Yet, if we had too MUCH melanin, we would not get enough sunlight (Vitamin D) and would become very sick as well. Therefore, the closer you are to the equator, or the more you are out in sunlight, the more melanin you have. But as you travel away from the equator or stay inside, your body needs to gather as much sunlight as possible to keep up vitamin D levels, so it reduces the melanin in your skin.

Sorry for the wall of text.

Pain gating is a super neat concept. Its amazing how your body prioritizes what pain is more urgent to notice.

The coolest thing in medschool I learnt was about Eagle Syndrome.

So you have these two pointy, bony spikes behind your jaw called your styloid processes.They are there as an anchor point for many ligaments including some from your tongue.

In some people the styloid processes are too long and it begins to compress on your carotid arteries leading up from your neck to your head. In most people this just results in neck pain and headaches, but in a minority these little stiletto knives can end up stabbing you in your carotids when turning your head, leading to you bleeding out and eventually dying.

I always seem to recall this fact when I have to answer a phone and pin it against my shoulder when I'm working. Spooky.

When your joint, for instance your knee joint, becomes sprained, it fills with fluid, called a joint effusion. That's your body's natural response, and it's like a natural splint, because you lose range of motion.