The digestive system발음듣기
대기중
The digestive system
119문장
100% 한국어
번역 11명 참여
출처 : 칸아카데미
번역
0%
I can't think of a better way to demonstrate the workings of the digestive system, the series of hollow organs that we use to break down and process nutrients and energy we need to function.발음듣기
대기중
Waiter! (lively music) The digestive system is so fundamental that it's basically step number one in the guide to how to make an animal.발음듣기
대기중
You probably remember that during the embryonic development of most animals the digestive tract is very first thing that forms.발음듣기
대기중
When the blastula, that little watt of cells that we all used to be turns into a little watt of cells with a tube running through it.발음듣기
대기중
Pretty much every animal has a digestive system of some kind, but their not all alike, far from it.발음듣기
대기중
For instance, a house fly eats mostly liquid or very finely granulated food but before it does that, it's got to puke it's digestive juices all over it's lunch and then let them digest it for awhile before it sucks it up into it's mouth.발음듣기
대기중
Most vertebrates put food in one end of the tube and our digestive system processes it and then it gets rid of the waste out the other end of the tube. No muss, no fuss.발음듣기
대기중
The beauty of it is that this whole process is run by our autonomic nervous system so we don't have to think about it until maybe the very last step when we're in traffic and just had two cups of coffee and a bran muffin, then we have to think about it a little bit.발음듣기
대기중
Among vertebrates, the digestive tract might be short or long, or have organs that do different things depending on what it's feeding habits are.발음듣기
대기중
The dog's digestive system has developed to take food in, absorb as many nutrients as possible and then to pass it onto somebody's lawn, all in a period of about six hours.발음듣기
대기중
Dogs have an extremely short digestive tract because if you're in the habit of eating rotten meat you better be able to digest it fast.발음듣기
대기중
If you don't, the bad bacteria that's probably living on that armadillo carcass is going to take up residence in your gut and put you in a world of hurt.발음듣기
대기중
[Tels] on the other hand take a very, very, very long time to digest their food around 80 hours because they have to process plants, mostly grass.발음듣기
대기중
Grass has a ton of cellulose in it and evolution has yet to produce an animal that can manufacture a stomach acid or an enzyme tough enough to break down cellulose.발음듣기
대기중
This process takes a four chambered stomach, each one with a slightly different micro ecology and a lot of cud chewing or regurgitating and re-chewing of grass before it passes all the way through.발음듣기
대기중
Nature is full of crazy digestion stories and I honestly wish that I had time to tell them all but let's focus on human digestion from now on.발음듣기
대기중
Mostly because you're probably a human, we don't assume anything here and you'll be wanting to know how your body does all these stuff.발음듣기
대기중
Two, humans actually have a pretty good all purpose digestive system we're omnivores after all, we eat plants and meat.발음듣기
대기중
Like most animals, humans have a bunch of different acids and enzymes in our digestive tracts that break down food, so that it can be absorbed and used by our bodies.발음듣기
대기중
The secret to successful digestion is maximizing surface area, in more that one way actually.발음듣기
대기중
Say I take a bite out of this apple, right now it's like an apple boulder sitting their in my mouth.발음듣기
대기중
The rest of my digestive system will have a really hard time dealing with it because most of the enzymes and acids would have the same difficulty working all the way through this big solid chunk.발음듣기
대기중
When I use my awesome teeth to chew up, there's chunk of apple suddenly there's double, triple, quadruple to surface area on the food.발음듣기
대기중
For humans, chewing is key because breaking down our food into smaller and smaller bits allows enzymes and acids to get it done.발음듣기
대기중
After our teeth have made the pieces small enough, the chemicals break them down further until their fine enough for our bodies to absorb nutrients from them.발음듣기
대기중
It's not just the surface area of the food that's important, the surface area of the digestive system is key to the whole process as well.발음듣기
대기중
Last time I talked about how we have a whole bunch of surface area in our lungs to absorb tons of oxygen all at once.발음듣기
대기중
Well our digestive system works in much the same way, most of the absorption of nutrients happens in our small inetstines and the length of the average human adult small intestine is about seven meters.발음듣기
대기중
Plus inside our small intestines there are a bunch of little folds, and little absorbing fibers with absorbing fibers on them, and no I didn't misspeak the fibers have fibers.발음듣기
대기중
Weh, it's kind of gross. I wouldn't want to see it spread out over a tennis court or anything, but I'm getting ahead of myself here.발음듣기
대기중
Now as you could see this hot pocket is surrounded by some kind of bread if you can call it that.발음듣기
대기중
The glands in my mouth start secreting saliva which contains salivary amylase, an enzyme designed to breakdown starch and glucose.발음듣기
대기중
The more I chew, the more amylase will get to all the different sides of the bread, and that's why the more you chew bread the sweeter it tastes.발음듣기
대기중
Amylase doesn't really do much with the meat or the cheese in this thing, I've got other enzyme and acids that are going to work on them later on in the system.발음듣기
대기중
I am going to chew all that stuff up real good right now so that those other enzymes can do their jobs later.발음듣기
대기중
Now the masticated hot pocket is passed down in my pharynx or throat and into my esophagus which leads to my stomach.발음듣기
대기중
Actually there's tittle cool flap of tissue called the epiglottis, that blocks the trachea when I swallow so that the food doesn't end up in my respiratory system.발음듣기
대기중
It's called a bolus and it rides a kind of wave, a muscle action down the esophagus into the stomach.발음듣기
대기중
This wave like contraction of the smooth muscles around the tube of the esophagus is called the peristalsis.발음듣기
대기중
Now my hot pocket bolus is in my stomach now which is where the food really starts getting man handled.발음듣기
대기중
It's like a churning cement mixture that can contract and expand with this big accordion like folds of muscles called rugae.발음듣기
대기중
The stomachs job it to turn everything over and over, smooching and mixing all the pieces up with it's cocktail of acids and enzymes called gastric juice.발음듣기
대기중
Gastric juices mainly made up of hydrochloric acid and enzyme called pepsin, and some mucus and water.발음듣기
대기중
Hydrochloric acid has a PH of about one which is strong enough that if you got in on your hand it would give you a chemical burn.발음듣기
대기중
The acid breaks things down and hopefully kills most of the bacteria that you might find on your food.발음듣기
대기중
Now that mucus is important, it's there to protect your stomachs so that it doesn't like digest itself.발음듣기
대기중
When you don't have enough of that mucus you get peptic ulcers which happen when your stomach lining comes in direct contact with your stomach acid.발음듣기
대기중
The water is just in there to make everything all soupy because what you want by the time your food leaves your stomach is chyme.발음듣기
대기중
Which is a kind of liquidy slop that you might be familiar with from the last time you had a stomach virus.발음듣기
대기중
Even this conversation's going to have to get a little bit gross and I didn't want to bring diarrhea into it too much because you know I've been eating.발음듣기
대기중
But when something bad is going on in your digestive tract your body doesn't worry too much about absorbing nutrients, it just wants to get the chyme out of there.발음듣기
대기중
Anyway there's a little valve or sphincter between the stomach and the small intestine that regulates how much chyme gets into the small intestine and when it gets in there.발음듣기
대기중
This is where a lot of the small intestine action happens by which I mean lots of things get absorbed and also secreted.발음듣기
대기중
Now the coolness of the small intestine can't be over stayed and it's ground zero for cellular exchange of nutrients in the breakdown of fats.발음듣기
대기중
Again the reason it's so good at absorbing is because all of the surface area has got going on.발음듣기
대기중
About that surface area, it comes from the fact that despite it's name your small intestine is freaking long.발음듣기
대기중
The whole inside is lined with epithelial tissue and has tons of ridges and folds in it, surface area to the max.발음듣기
대기중
Get this, each villus which is only like half a millimeter long is covered in teeny tiny little micro villi providing even more surface area.발음듣기
대기중
Another thing the small intestine does with the help of it's friend the gallbladder is break down fatty stuff, like this milkshake.발음듣기
대기중
In the top of your small intestine is a little pipe where bile salts manufactured by the liver and stored by the gallbladder are squirted out into the small intestine.발음듣기
대기중
It takes hydrophobic fat molecules and breaks them up into fatty acids and monoglycerides which can be absorbed by all that epithelial tissue.발음듣기
대기중
Nuts. After your food passes through those yards and yards of small intestine the chyme goes through another sphincter and enters the cecum, the beginning of the large intestine.발음듣기
대기중
The large intestines job is to remove most of the water and bile salts from the chyme, so you don't have constant diarrhea.발음듣기
대기중
It's basically just a one and half meter victory lap around the outside of the small intestine and then it calls it good.발음듣기
대기중
Also should mention at the end of the cecum there's a little tube where the appendix comes in.발음듣기
대기중
For a long time we thought that the appendix was a worthless vestibule structure that we used to need at some point in our evolution but didn't need anymore.발음듣기
대기중
However, recent studies are finding that the purpose of the appendix in modern humans is probably to act as a safe house for all the good bacteria you need to help you digest your food.발음듣기
대기중
If you get a virus or food poisoning or something and all your digestive system say "Get all out of me."발음듣기
대기중
The appendix has a little sample of your gut bacteria that it spits out to help you recolonize after your illness.발음듣기
대기중
I think you're probably familiar with the final step in the digestive system that's the pooping.발음듣기
대기중
Your food can spend as long as three days in your digestive tract and a lot of that time is spent in the large intestine.발음듣기
대기중
Mostly reabsorbing the excess water from the chyme and prepping your poo for it's great entrance into the world.발음듣기
대기중
칸아카데미 더보기더 보기
-
106문장 100%번역 좋아요2
번역하기 -
Presidential signing statements
53문장 100%번역 좋아요1
번역하기 -
87문장 100%번역 좋아요3
번역하기 -
Classical Japan during the Heian Period | Wor...
23문장 100%번역 좋아요1
번역하기
