People Are Just realising This 1 Wild Fact About The Brain, And I'm Still In Shock

"Everything I learn about the meat mech has been against my will and uncomfortable."
Carol Yepes via Getty Images

We’ve written before at HuffPost UK about how animal bodies can be far weirder than you’d realise.

But the human brain? Yeah, that’s a special kind of odd.

In a recent TikTok, microbiologist @mariedoesstuff revealed that her neuroscientist friend “deeply upset [her] with some brain facts, and so I’m gonna share.”

And to be honest, I haven’t recovered since.

What are they?

Well, let’s start strong ― most of the “brain” part of your brain straight-up doesn’t have blood in it.

The scientist said her friend was explaining the choroid plexus, a “structure in your brain that filters your blood to make cerebrospinal fluid.”

Though there are miles of capillaries in the brain, and though brains demand 20% of our blood despite only taking up 2% of our bodies, “not a single neuron ever touches a capillary.”

Neuroscience-based YouTube channel Neuroscientifically Challenged breaks this down further, explaining that the barrier between the two “prevents toxins, pathogens, and other potentially dangerous substances from crossing from the circulatory system into the brain.”

In fact, her friend’s favourite fact is that “every single neuron is within 50 micrometres of a capillary for gas exchange ― but there are no blood products in the brain.”

That means no blood cells, no lymph, no blood proteins, she says (though Neuroscientoifically Challenged says that some areas, like the circumventricular organs, “lack a blood-brain barrier” as parts of it, like the pituitary gland, need to release hormones into the blood).

“I am deeply uncomfortable with this,” the TikToker said.

Thought we were done? We’re not

Though the brain is undoubtedly odd, there’s at least a crumb of sense in it all ― “the phrase ‘blood-brain barrier’ makes so much more sense now,” the microbiologist said.

But don’t calm down just yet; her friend also mentioned the brain’s ventricles, which are “kind of like a purposeful hole in the brain” that keeps it floating.

People had thoughts in the comments, with one TikTok user writing, “Everything I learn about the meat mech has been against my will and uncomfortable.”

“Makes sense why a brain bleed is so bad then I guess, I never knew that,” another said.

“It’s just gas exchange? So I really am an airhead?” yet another app user joked, to which the original poster of the view replied, “We all are.”

What a world.


I don’t do bodies. Last time I learned anything about the human body was HS, and I don’t think I regret that. #microbiologist #brain #brainfacts #neurobiology

♬ original sound - mariedoesstuff