Welcome to brain Stuff from How Stuff Works. Hi, brain Stuff listeners. I'm Lauren voc Obam, and today's episode is another brain Stuff classic from our former host, Christian Sagar. We're delving into perhaps the most important biological question known to humankind. What are eyeboggers? A brain stuff Christian Sager Here, Today's question is what our eyeboggers. If you've ever had to wipe gunk out of the corner of your eyes, it's not because you were visited by the Sandman or
a magical mucus ferry. Nope, we live in a cruelly mundane universe, and I'm sorry if I'm the first to break it to you, but eyeboggers are a build up of the pre corneal or basil tier film that coats and protects your eyes, plus any foreign particles it catches. This tier film is just three micrometers thick, which is less than half the diameter of a red blood cell. But it's made up of three components, the mucin, the aqueous, and the lipid. These are indistinct layers of stuff that
your body produces. The aqueous component is the operative one. It nourishes, lubricates, and flushes your eyes cells. It also smooths over microscopic lumps and bumps on the surface of your eyes, creating a smooth lens that optimizes light transfer into your retina. The other two components are a support system for the aqueous one. The musing component underneath it allows it to temporarily stick to your eye, and the lipid component outside it holds it in place so that
you're not just you know, crying constantly. So closest to your corneal surface cells, you've got the musing component of the tear film. Mucins are the proteins that make mucus slimy. They're important in your eyes because corneal cells. Your corneal cells need water and water soluble new reents, but your corneal cells, unhelpfully are hydrophobic, meaning they repel water like
microscopic little ducks. Mucin helps out by latching onto your corneal cells, specifically via adhesive molecules called glycocalyx that grow on the cell's surface, and mucans are hydrophilic, meaning that they grab onto water molecules. Next up the aqueous component. As you may have guessed from the name, this layer is made up of about water plus two percent water soluble stuff at any given time. Part of that two percent is things your corneal cells need, like electrolytes, oxygen,
and antibacterial enzymes, and part is the cell's waste. There are also some musans floating around in there, and usually some dust debris, and you know sun dream microbes. Finally, topping it all off, you've got the lipid component a k a. The me bum. It's made mostly of wax and cholesterol esters. These esters are slick, hydrophobic substances that our bodies used to lubricate and waterproof various tissues in the tear film. They float on top of the aqueous layer,
helping our eyelids glide easily over our eyes. They also provide a strong surface tension for our basil tears. Without the lipid layer, our tear film would drip right off our eyeballs. But how do these components become eyeboggers and why do they accumulate in the inner corners of your eyes. Well, I'm gonna tell you. When you blink, your entire eyelid doesn't close simultaneously. It shuts like a clapboard from the outer corners of your eyes inward towards your nose, your
tear film gets pushed along by that motion. Upon reaching the inner corner of your eye, most of the film drains out through the tear ducts, which empty into your nasal cavity, and some of the film, the mucin and oils and debris, can clump together and get stuck. When enough of that builds up, it forms the goop known as eyeboggers, and when it accumulates and dries overnight because you're not blinking it away, it forms the crusty gunk
known as sleep or SAM. Today's episode was produced by Tyler Clang and written by me for brainstuffs YouTube series in the Way Back. If you like our show and also like not being naked, check out our merch store at t public dot com slash brainstuff, and of course, for more on this and lots of other gross but fascinating topics, visit our home planet, how Stuff Works dot com