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  • You know how it feelsthat crushing headache, a building pressure in your face, and thick mucus dripping down the back of your throat.

  • Sinusitis, or sinus infections, are incredibly common

  • and no fun whatsoeveranywhere from thirty to thirty five million sinus infection diagnoses

  • are made every year in the USThey're one of those sicknesses that usually go away

  • on their own, but they're a nuisance nonetheless. And in fact, our tendency to get sinus infections

  • might actually be a quirk of human evolution.

  • There's dust, pollution, and pathogens like

  • viruses and bacteria in every breath we take, and one tool that our body uses to keep us

  • healthy is our nasal cavities. Within the fleshy nose itself, hair and mucus catch big

  • dust particles, which is a good first line of defense for keeping our lungs clean. From

  • there, our breath enters a series of air-filled chambers behind the facial bones called the

  • paranasal sinuses. Paranasal for around the nose, sinus for empty space. Their first job

  • is to warm and humidify air, making it easier to breathe when it gets down to the lungsThe

  • next line of defense is mucusand it's totally normal. We're all secreting at least

  • a little mucus all the timeEach of our sinuses are lined with cells that can make

  • more or less mucus depending on the situation, they're also coated in cells that have little

  • hairlike structures called cilia. These things wiggle back and forth to keep this mucus moving

  • down collection ducts in each of our sinuses where they drain into the nasal cavity, then

  • into the throat. This becomes more complicated when you get a sinus infection. Which is exactly

  • what it sounds likeinfection from pathogens or allergens that stick around in your sinuses,

  • like from a cold or flu, which then causes inflammation of these mucus membranes. Most

  • of the time, these pipes and chambers flow freely, and we can take big clear breaths.

  • But when sinuses have to deal with germs, it results in clogged up noses and difficulty

  • breathing. Viruses cause the majority of sinus infections, but bacteria can trigger them

  • as well. When you do get a sinus infection, that wet mucus gets thicker and more viscous,

  • which causes the typical symptomscongestion, headache, and difficulty breathing. And those

  • symptoms might be made worse by the plumbing of our sinusesEach sinus has a mucous

  • collection duct, or what are called ostia, to shuttle its discarded mucous to the nose

  • and throat. It's basically plumbing for snot. Well for most of our sinuses like the

  • frontal sinuses behind the forehead or the sphenoid sinuses a few centimeters behind

  • our eyes, the collection duct is towards the bottom of the sinusThe ethmoid sinus has

  • a bunch of tiny cavities that it drains out of, but it still drains downward. The big

  • exception then is the maxillary sinusesthe ones behind our maxillas, or upper lip and

  • cheeks area. These are our biggest sinuses, at about 15 milliliters and the ones that

  • most often get infected. For most humans, we have one collection duct towards the top

  • innermost wall of the maxillary sinus. Having the collection duct at the top of sinus might

  • keep us from draining all that collected snot more efficiently. Which in turn might predispose

  • humans to sinus infectionsOn one hand, if you have a sinus infection, your cilia

  • have to wick a bunch of thick, viscous mucus towards the collection duct against gravity,

  • and that mechanism tends not to work as well when we have an infection. So we end up with

  • more and more bacteria which creates infinite snot and makes symptoms worse. On the other

  • hand, that duct might act like an overflow drainThat's why it sometimes helps to

  • lie down or bend forward when you have a sinus infectionit helps drain mucus towards

  • the ducts. Obviously that doesn't remove the infection, but it might help for a little

  • bit. Ultimately the location of the maxillary ostia is a consequence of evolving from ancestors

  • that walked around on four legs. Asking whether our bodies would work better if it had different

  • anatomy is a hard question to test scientifically, so researchers might compare our anatomy to

  • a different animal's. Like in the past decade, scientists published a paper where they filled

  • human sinuses and goat sinuses with a saline solution and measured how quickly they drained.

  • In an upright position, the human sinuses didn't drain that well, but when they were

  • tilted forward, they drained as quickly as the goats' didOn a practical level, different

  • scientists also showed that moving into the quadrupedal head position, essentially just

  • leaning forward, does relieve sinusitis symptoms. That makes them think that the location of

  • the sinus ostia was appropriate for our four legged ancestors, but not for modern humans

  • on two legs. But, it's also worth remembering that everyone has slightly different nasal

  • anatomy which might predispose some people to sinus infections more than others. While

  • our sinuses might be designed less than ideally, having a big brain was more important, so

  • we're left with the nasty, snotty consequences of evolution. While we can't go back in

  • time to say if this was a good or bad design, our sinuses are something that make us Human

  • Thanks for watching this episode of Seeker Human. We're so excited to get more episodes of Human to you

  • just a little bit, so make sure you're subscribed on YouTube and following us on social media

You know how it feelsthat crushing headache, a building pressure in your face, and thick mucus dripping down the back of your throat.

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C1 mucus duct infection collection drain snot

Why Do Humans Get So Many Sinus Infections?

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    林宜悉 posted on 2020/12/26
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