血壓是如何運作的 - Wilfred Manzano：英語精讀講義

If you lined up all the blood vessels in your body, 講解

如果把你體內所有的血管連起來，

they'd be 95,000 km long.

它們的長度會達到 9.5 萬公里。

And every day, they carry the equivalent 片語搭配

它們每天輸送的血液量，

of over 7,500 L of blood.

相當於超過 7500 公升血液。

Though that's actually the same 4 or 5 L 表達脈絡

儘管這實際上只是那相同的 4 到 5 公升血液

recycled over and over, 片語搭配

在不斷地循環，

delivering oxygen and precious nutrients 片語搭配

將氧氣和珍貴的營養物質，

like glucose and amino acids to the body's tissues.

如葡萄糖和胺基酸，輸送到全身組織。

All that blood exerts a force 片語搭配

所有這些血液都會對

on the muscular walls of the blood vessels.

血管肌肉壁施加一種力量。

That force is called blood pressure,

這種力量被稱為血壓，

and it rises and falls with the phases of the heartbeat. 片語搭配

它會隨著心跳的節奏而升高和降低。

It's highest during systole, 用詞

它在收縮期達到最高值，

when the heart contracts to force blood through the arteries.

此時心臟收縮，將血液擠壓進動脈。

This is your systolic blood pressure.

這就是你的收縮壓。

When the heart is at rest between beats, 片語搭配

當心臟在兩次跳動之間休息時，

blood pressure falls to its lowest value,

血壓降到最低值，

the diastolic pressure. 用詞

即舒張壓。

A typical healthy individual produces a systolic pressure

一個典型的健康個體的收縮壓

between 90 and 120 mm of mercury 文化背景

在 90 到 120 毫米汞柱之間，

and diastolic pressure between 60 and 80.

而舒張壓在 60 到 80 之間。

Taken together, a normal reading 表達脈絡

綜合來看，正常的讀數

is a bit less than 120 over 80. 用詞

會略低於 120/80。

The blood traverses the landscape of the body

血液穿越身體各個角落的途徑，

through the pipes of the circulatory system. 表達脈絡

就是透過循環系統這些「管道」。

In any plumbing system,

在任何管道系統中，

several things can increase the force on the walls of the pipes,

有幾個因素會增加管壁承受的壓力，

the properties of the fluid, extra fluid, or narrower pipes.

即流體特性、流體增多或管道變窄。

So if the blood thickens, 文法

因此，如果血液變稠，

a higher pressure is needed to push it,

就需要更高的壓力來推動它，

so the heart will pump harder.

心臟就得更用力地泵血。

A high salt diet will lead to a similar result. 片語搭配

高鹽飲食也會導致類似的結果。

The salt promotes water retention, 用詞

鹽會促使體內水分瀦留，

and the extra fluid increases the blood volume and blood pressure.

多餘的水分會增加血容量並升高血壓。

And stress, like the fight or flight response, 文化背景

另外，壓力，比如「戰或逃」反應，

releases hormones like epinephrine and norepinephrine

會釋放腎上腺素和正腎上腺素等荷爾蒙，

that constrict key vessels, 用詞

使關鍵血管收縮，

increasing the resistance to flow 用詞

增加血流阻力，

and raising the pressure upstream. 用詞

並提高上游的血壓。

Blood vessels can usually handle these fluctuations easily.

血管通常能輕鬆應對這些波動。

Elastic fibers embedded in their walls make them resilient.

血管壁內嵌的彈性纖維使其具有彈性。

But if your blood pressure regularly rises

但如果你的血壓經常升高

above about 140 over 90,

到 140/90 以上，

what we call hypertension, and stays there, 片語搭配

也就是我們所說的高血壓，並保持在這個數值，

it can cause serious problems.

就會引發嚴重的問題。

That's because the extra strain on the arterial wall 講解

這是因為動脈壁承受的額外壓力

can produce small tears.

會產生微小的撕裂。

When the injured tissue swells up, 片語動詞

當受損組織腫脹時，

substances that respond to the inflammation,

對發炎做出反應的物質，

like white blood cells, collect around the tears.

如白血球，就會聚集在撕裂處周圍。

Fat and cholesterol floating in the blood latch on too, 片語動詞

血液中漂浮的脂肪和膽固醇也會附著上去，

eventually building up to form a plaque 片語動詞

最終堆積形成斑塊，

that stiffens and thickens the inner arterial wall.

使動脈內壁變硬變厚。

This condition is called atherosclerosis, 用詞

這種情況被稱為動脈粥狀硬化，

and it can have dangerous consequences.

它可能會導致危險的後果。

If the plaque ruptures,

如果斑塊破裂，

a blood clot forms on top of the tear,

撕裂處上方就會形成血栓，

clogging the already narrowed pipe. 表達脈絡

堵塞本已變窄的血管。

If the clot is big enough, 文法

如果血栓足夠大，

it can completely block the flow of oxygen 片語搭配

它就能完全阻斷氧氣

and nutrients to cells downstream. 用詞

和營養物質流向下游細胞。

In vessels that feed the heart, 用詞

在為心臟供血的血管中，

that will cause a heart attack,

這會導致心臟病發作，

when oxygen-deprived cardiac muscle cells start to die. 用詞

因為缺氧的心肌細胞會開始死亡。

If the clot cuts off blood flow to the brain, 片語動詞

如果血栓切斷了流向大腦的血液，

it causes a stroke.

就會導致中風。

Dangerously clogged blood vessels can be widened

嚴重堵塞的血管可以透過

by a procedure called an angioplasty. 用詞

一種叫做「血管成形術」的手術來擴張。

There, doctors thread a wire through the vessel 用詞

在手術中，醫生透過血管穿入一根導線，

to the obstructed site,

一直到達阻塞部位，

and then pass a deflated balloon catheter over the wire. 用詞

然後沿著導線送入一個未充氣的氣球導管。

When the balloon is inflated,

當氣球充氣時，

it forces the passageway open again. 片語搭配

它會強行將通道再次撐開。

Sometimes a rigid tube called a stent 用詞

有時也會在血管中放置一個

is placed in the vessel to help hold it open, 片語搭配

叫做「支架」的剛性管以幫助保持血管暢通，

letting the blood flow freely to replenish 用詞

讓血液自由流動，以補充

the oxygen-starved cells downstream.

下游急需氧氣的細胞。

Staying flexible under pressure 慣用語

在壓力下保持柔韌性

is a tough job for arteries.

對動脈來說是一項艱巨的工作。

The fluid they pump is composed of substances 片語搭配

它們泵送的流體所包含的物質

that can get sticky and clog them. 用詞

可能會變得黏稠並堵塞血管。

And your typical healthy heart

而你那典型的健康心臟

beats about 70 times a minute

每分鐘大約跳動 70 次，

and at least 2 and a half billion times

在平均一生中，

during an average lifetime.

至少會跳動 25 億次。

That may sound like an insurmountable amount of pressure, 表達脈絡

這聽起來像是一個無法承受的壓力，

but don't worry.

但別擔心。

Your arteries are well-suited for the challenge. 片語搭配

你的動脈完全能夠應對這個挑戰。