How your digestive system works - Emma Bryce

譯者: Helen Chang 審譯者: S Sung

Across the whole planet,

世界上的人

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

每天平均吃下 1 至 2.7 公斤的食物

That's over 365 kilograms a year per person,

每人每年吃了 超過 365 公斤的食物

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

一生吃了超過 28,800 公斤的食物

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

一點也不剩地全都經過了消化系統

Comprised of ten organs covering nine meters,

消化系統包括十個器官，長達九公尺

and containing over 20 specialized cell types,

且有超過 20 種各式專門的細胞

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

是人體中最多樣、最複雜的系統之一

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

各部分不斷同心協力 完成一項特殊的任務

transforming the raw materials of your food

把消化的食物轉換成

into the nutrients and energy that keep you alive.

身體所需的營養及能量

Spanning the entire length of your torso,

範圍跨越整個軀幹的消化系統

the digestive system has four main components.

有四個主要組成部分

First, there's the gastrointestinal tract,

首先是胃腸道

a twisting channel that transports your food

一個運輸食物的扭曲通道

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

它內部的表面積介於 30 到 40 平方公尺之間

enough to cover half a badminton court.

足以覆蓋半個羽毛球場

Second, there's the pancreas,

其次是胰臟、膽囊及肝臟

gallbladder,

and liver,

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

是利用一系列特殊消化液 來分解食物的三個器官

Third, the body's enzymes,

第三是體內的酶

hormones,

激素

nerves,

and blood

神經

及血液

all work together to break down food,

協同分解食物

modulate the digestive process,

調節消化過程

and deliver its final products.

送出最終的產物

Finally, there's the mesentery,

最後是腸繫膜

a large stretch of tissue that supports

這一大塊可伸縮的組織

and positions all your digestive organs in the abdomen,

支撐和固定腹內所有的消化器官

enabling them to do their jobs.

使他們能做好分內的工作

The digestive process begins before food even hits your tongue.

消化的過程在你的舌頭 尚未碰觸到食物時已經開始了

Anticipating a tasty morsel,

預期美味食物的到來

glands in your mouth start to pump out saliva.

你嘴裡的腺體開始分泌唾液

We produce about 1.5 liters of this liquid each day.

我們每天約產出 1.5 升這種液體

Once inside your mouth,

一旦食物進入嘴裡

chewing combines with the sloshing saliva

咀嚼結合唾液

to turn food into a moist lump called the bolus.

把食物變成潮濕的食團

Enzymes present in the saliva break down any starch.

唾液中的酶分解掉所有澱粉

Then, your food finds itself

然後食物來到

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

25 公分長「食道」的邊緣

down which it must plunge to reach the stomach.

再掉進胃裡

Nerves in the surrounding esophageal tissue

食道周圍的神經

sense the bolus's presence and trigger peristalsis,

感覺到食團的存在而引發蠕動

a series of defined muscular contractions.

那是一系列明確的肌肉收縮動作

That propels the food into the stomach,

把食團推進胃

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

任由胃壁的肌肉

which bound the bolus, breaking it into chunks.

把食團分成了小塊

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

內膜細胞分泌的激素

引發胃壁分泌胃酸和酶

and enzyme-rich juices from the stomach wall

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

開始溶解食物並分解蛋白質

These hormones also alert the pancreas,

這些激素還會使胰、肝和膽囊

liver,

and gallbladder

to produce digestive juices

產生消化液

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

傳送黃綠色消化脂肪的膽汁

in preparation for the next stage.

為下一階段做好準備

After three hours inside the stomach,

在胃裡面三個小時之後

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

曾經有型的食團 現在是泡沫液體狀的食糜

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

準備好要進入小腸了

The liver sends bile to the gallbladder,

肝臟收到膽囊的膽汁

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

把它送到小腸的第一段

稱為「十二指腸」

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

漂浮在食糜中的脂肪在這裡被溶解

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

使它們可以很容易

被澆淋到此的胰液和腸液消化

that have leached onto the scene.

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

這些富含酶的消化液

將脂肪分子分解成脂肪酸和甘油

and glycerol for easier absorption into the body.

讓身體更容易吸收

The enzymes also carry out the final deconstruction

最終酶也把蛋白質分解成胺基酸

of proteins into amino acids

and carbohydrates into glucose.

把碳水化合物分解成葡萄糖

This happens in the small intestine's lower regions,

這發生在小腸下部區域的

the jejunum and ileum,

「空腸」和「迴腸」

which are coated in millions of tiny projections called villi.

它們包覆著數百萬個 稱為「絨毛」的細小突起

These create a huge surface area to maximize molecule absorption

使腸的表面積變得非常廣大

能極大化分子的吸收

and transference into the blood stream.

再轉移到血液中

The blood takes them on the final leg of their journey

血液帶它們走上最後一段旅程

to feed the body's organs and tissues.

為人體的器官和組織提供營養

But it's not over quite yet.

但是還沒完

Leftover fiber,

殘留的纖維、水

water,

and dead cells sloughed off during digestion

和消化過程中脫落的死細胞

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

進入大腸，也稱為「結腸」

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

身體由腸壁排出大部分的殘餘液體

What's left is a soft mass called stool.

剩下的柔軟物質稱為糞便

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

結腸將這副產物擠壓到 被稱為「直腸」的袋子裡面

神經感覺到膨脹

where nerves sense it expanding

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

告訴身體什麼時候該排出廢物

The byproducts of digestion exit through the anus

消化的副產物由肛門排出

食物的長途旅程

and the food's long journey,

typically lasting between 30 and 40 hours,

通常持續 30 至 40 小時

is finally complete.

終於完成了