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There are thin cells called pericytes wrapped around the small blood vessels, and around that you have extensions of astrocyte cells. The barrier is too small to see with the naked eye.

What is the blood-brain barrier physically made of? If I opened a head, what would it look like?

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Yes it can. During any infection of the CNS the blood brain barrier becomes more porous for everything, and people experience CNS symptoms. If the infection destroyed some neurons, those don't grow back. CNS neuronal damage is permanent.

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Can blood/brain barrier be breached by bacterial infection thus damaging the brain? I am asking this because someone close to me was recently treated for sepsis and infection on spine, left the hospital but is now investigated for dementia due to saviour symptoms that started during the infection? Just wondering 🤔

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Great explain, thank you very much!

Well, what they are saying is that blood, and its contents, have some direct detrimental effects, but the most immediate, significant damage is due to secondary effects of all the leaking blood. When blood escapes the vessels, it builds up, and causes pressure to increase within the skull, harming the brain. Also, with the controlled flow of the blood interrupted, the brain does not get the oxygen it needs. These are factors secondary to the blood flow no longer being controlled by vessels.

 

The direct effects of disruption of the blood-brain-barrier (neurons exposed to inappropriate stuff/concentrations of stuff, and products of decomposing RBCs) is indeed damaging, but it is the deprivation of oxygen that has the most, lasting effect. The neurons recover from the damaging, but not so lethal, effects created by the presence of blood, but the secondary lack of oxygen, is what kills the neurons.

Not really, New Zealand is continental crust, the micro continent of zealandia

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I've never managed to get a straight answer I can wrap my head around for why light slows down in refractive media. Turns out "we don't know for sure and there's lots of heated disagreement on it" was the actual answer I needed. Thank you.

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Yup! Your brain sits in a bath not of blood, but a different substance called cerebrospinal fluid (CSF). It is on the "internal' side of the blood brain barrier. Nutrients and water diffuse across the blood brain barrier through very fine capillaries. Blood is too thick and "sticky" for the brain to be able to use while still performing its role. CSF itself is almost entirely water - about 99%. CSF also serves to cushion your brain and act as an immunological barrier between your brain and the rest of your body.

In addition, most organs are adversely affected by direct contact with blood. You don't want blood in your stomach or kidneys or liver either! Blood is meant to stay in your blood vessels and diffuse nutrients across various tissue barriers while the glymphatic / lymphatic systems draw metabolic and immunologic waste away to be excreted.

I know this isn't a perfect analogy, but I'm imagining like how fuel and air power the combustion in an engine, but you wouldn't want it in the oil system.

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There's also the factor of initial viral load.

Jack gets covid, has no symptoms, and only notices because his work did a random screen.

Jane gets covid and dies from lung failure.

Maybe Jack got a single viral particle and his body had plenty of time to ramp up is response but Jane got coughed on by someone chock full o virus and by the time she started producing antibodies her lungs were already saturated.

Getting stuff off the moon (or asteroids) and into orbit around Venus would be way cheaper than getting materials off of Earth or Mars, so that's one option

Turtles sort of cheat their way into having an "exoskeleton", but it's not a true one. The carapace is comprised of modified vertebrae (neural bones) and ribs (costal and peripheral bones). The plastron was once thought to be a modified sternum, but it actually seems to be composed of the clavicles and gastralia, a structure found only in reptiles.

Turtles have all the same bones as other vertebrates, and their internal organs are still housed within a body cavity protected by bone. They've just gone a little overboard with the level of protection. One can jokingly refer to their shell as an exoskeleton, but it is in reality a highly modified endoskeleton.

Turtle morphology is endlessly fascinating and has baffled researchers for decades, both in terms of how they relate to one another and how they relate to other reptiles. We're finall starting to parse them out based on genetics, but even still it's tricky and involved. I don't deal with genetics though, I just put my faith in the geneticists.

Also, pooled non-circulation blood is an infection risk. "Bacteria love blood."