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Eyeballs are … weird.
They’re these strange little blobs that sit inside your skull,
and there’s nothing else in your body quite like them.
They aren’t bone, but they aren’t soft like the tissue under your skin, either.
Most of your eyeball isn’t even that white stuff you see from the outside.
Most of your eye is actually a clear, jelly-like type of collagen,
the same kind of structural protein that gives your nose and ears their shape.
The whiteness you see when you look at your eye is the sclera
the outer layer that holds the whole sac of goo together.
But it’s just a tough, thin outer coat.
The sclera covers everywhere except the very front of your eyeball, where it connects to
the clear tissue that makes up your cornea.
It’s clear so that it lets in light, just so you can actually see.
Then there’s all that stuff that helps the light get to the back of your eye.
After it comes through the cornea, light reaches the colorful part of your eye next, the iris.
Its main job is to control the size of your pupils
so that the right amount of light gets further in.
Directly behind the iris is a lens, a hard, glass-like structure that does
exactly what it sounds like: it focuses the light.
Meanwhile, the retina, which is actually what does the seeing, is all the way in the back.
It contains light-sensitive cells, as well as the system of nerves that are hooked up
to your optic nerve to tell your brain what you’re looking at.
But there’s still a lot, a LOT of space left in your eyeball.
And most of it, 80% of your eyeball by volume,
is the clear, gel-like substance that sits between the retina and the lens.
That gooey stuff is called the vitreous humor or the vitreous body, and it’s there
as a shock absorber and for structural support.
Vitreous humor is latin for ‘glassy fluid,’ referring to the fact that the goo is clear.
Like most gels, it’s mostly water, which is mixed with collagen fibers
and a kind of sugar called hyaluronic acid.
So yeah. Your eyeball is mostly sweet, gooey collagen.
There are also lots of other things sprinkled around in really low amounts: more than 120
distinct proteins have been found in the vitreous humor.
It’s actually a littler gooier in the center, and firmer toward the edges.
And as you age, it all gets a bit more liquidy.
That can cause it to separate from the retina in some places,
casting those little moving shadows we call floaters.
There’s also another fluid, called the aqueous humor,
in front of the lens, sandwiched between your iris and your cornea.
That gel takes up most of the remaining 20% of your eyeball’s volume, and as the name
suggests, it’s more watery than the vitreous humor.
It’s there to nourish your cornea, in addition to making sure your
eye remains the right shape.
What it doesn’t contain is blood, or hemoglobin, or any other way of
delivering oxygen to those see-through cells in the front.
Which makes sense, because you wouldn’t want red stuff
getting in the way of you seeing things.
The cornea doesn’t have blood, either, or it wouldn’t be clear.
So it has to get the oxygen it needs another way: from the gas dissolved in your tears.
Which means… your cornea basically breathes on its own.
Your eyeball. Breathes.
There’s not a lot of oxygen in tears, but it’s just enough to give the corneal cells
what they need to stay alive so the whole sack of goo doesn’t fall apart.
Now, for something to feast your eyeballs on:
A few episodes ago we told you that we would transition our old scishow.com website into
a shiny new Squarespace site, so here’s how that’s coming along.
We could look at the demo for various templates and get a feel for which would be the best
for showcasing SciShow and its 3 spinoff channels, plus Patreon and merchandise.
We browsed through dozens, but the navigation menu made it easy for us to rule out
blog-style and long scrolling designs.
Considering what we needed for the new SciShow site, we debated longest between Montauk and
Bedford templates, and ended up choosing Bedford.
Follow our progress in an upcoming video to see how we decide to
build the pages and the text.
And if you have a million dollar idea that you’ve been meaning to launch,
now is the time.
Use Squarespace to bring it to life, and go to squarespace.com/scishow for a free trial.
Make sure to use the offer code to support this channel and save 10%
off your first purchase of a website or domain.
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