Интересности на английском языке! Детям о том, как работает наша пищеварительная система.

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Across the whole planet,

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humans eat on average between one and 2.7 kilograms of food a day.

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That's over 365 kilograms a year per person,

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and more than 28,800 kilograms over the course of a lifetime.

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And every last scrap makes its way through the digestive system.

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Comprised of ten organs covering nine meters,

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and containing over 20 specialized cell types,

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this is one of the most diverse and complicated systems in the human body.

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Its parts continuously work in unison to fulfill a singular task:

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transforming the raw materials of your food

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into the nutrients and energy that keep you alive.

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Spanning the entire length of your torso,

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the digestive system has four main components.

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First, there's the gastrointestinal tract,

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a twisting channel that transports your food

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and has an internal surface area of between 30 and 40 square meters,

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enough to cover half a badminton court.

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Second, there's the pancreas,

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gallbladder,

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and liver,

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a trio of organs that break down food using an array of special juices.

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Third, the body's enzymes,

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hormones,

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nerves,

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and blood

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all work together to break down food,

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modulate the digestive process,

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and deliver its final products.

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Finally, there's the mesentery,

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a large stretch of tissue that supports

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and positions all your digestive organs in the abdomen,

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enabling them to do their jobs.

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The digestive process begins before food even hits your tongue.

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Anticipating a tasty morsel,

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glands in your mouth start to pump out saliva.

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We produce about 1.5 liters of this liquid each day.

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Once inside your mouth,

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chewing combines with the sloshing saliva

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to turn food into a moist lump called the bolus.

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Enzymes present in the saliva break down any starch.

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Then, your food finds itself

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at the rim of a 25-centimeter-long tube called the esophagus,

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down which it must plunge to reach the stomach.

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Nerves in the surrounding esophageal tissue

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sense the bolus's presence and trigger peristalsis,

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a series of defined muscular contractions.

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That propels the food into the stomach,

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where it's left at the mercy of the muscular stomach walls,

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which bound the bolus, breaking it into chunks.

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Hormones, secreted by cells in the lining, trigger the release of acids

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and enzyme-rich juices from the stomach wall

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that start to dissolve the food and break down its proteins.

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These hormones also alert the pancreas,

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liver,

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and gallbladder

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to produce digestive juices

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and transfer bile, a yellowish-green liquid that digests fat,

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in preparation for the next stage.

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After three hours inside the stomach,

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the once shapely bolus is now a frothy liquid called chyme,

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and it's ready to move into the small intestine.

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The liver receives bile from the gallbladder

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and secretes it into the first portion of the small intestine called the duodenum.

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Here, it dissolves the fats floating in the slurry of chyme

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so they can be easily digested by the pancreatic and intestinal juices

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that have leached onto the scene.

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These enzyme-rich juices break the fat molecules down into fatty acids

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and glycerol for easier absorption into the body.

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The enzymes also carry out the final deconstruction

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of proteins into amino acids

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and carbohydrates into glucose.

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This happens in the small intestine's lower regions,

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the jejunum and ileum,

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which are coated in millions of tiny projections called villi.

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These create a huge surface area to maximize molecule absorption

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and transference into the blood stream.

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The blood takes them on the final leg of their journey

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to feed the body's organs and tissues.

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But it's not over quite yet.

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Leftover fiber,

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water,

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and dead cells sloughed off during digestion

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make it into the large intestine, also known as the colon.

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The body drains out most of the remaining fluid through the intestinal wall.

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What's left is a soft mass called stool.

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The colon squeezes this byproduct into a pouch called the rectum,

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where nerves sense it expanding

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and tell the body when it's time to expel the waste.

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The byproducts of digestion exit through the anus

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and the food's long journey,

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typically lasting between 30 and 40 hours,

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is finally complete.