How blood pressure works - Wilfred Manzano

譯者: Wink Wong 審譯者: Max Chern

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

如果你把身體的血管排成直線

they'd be 95,000 kilometers long

長度會有9萬5千公里長

and everyday, they carry the equivalent of over 7,500 liters of blood,

每天輸送相當於超過 7千5百公升的血液

though that's actually the same four or five liters recycled over and over,

事實上只是相同的 4至5公升血液反覆循環

delivering oxygen, and precious nutrients

輸送氧氣和重要養份

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

例如葡萄糖 和胺基酸到身體各處

All that blood exerts a force on the muscular walls of the blood vessels.

血液會對血管壁施加壓力

That force is called blood pressure,

這種施力稱為血壓

and it rises and falls with the phases of the heartbeat.

它隨著心跳週期有升有降

It's highest during systole,

當心臟收縮

when the heart contracts to force blood through the arteries.

迫使血液流入動脈 的收縮期，血壓最高

This is your systolic blood pressure.

這就是收縮壓

When the heart is at rest between beats,

當心臟在兩跳之間休止

blood pressure falls to its lowest value, the diastolic pressure.

血壓降到最低，這叫做舒張壓

A typical healthy individual produces a systolic pressure

一個正常人的收縮壓

between 90 and 120 millimeters of mercury,

介於90至120毫米汞柱之間

and diastolic pressure between 60 and 80.

而舒張壓則介於60至80毫米汞柱之間

Taken together, a normal reading is a bit less than 120 over 80.

合在一起，正常的 血壓值略低於120 /80

The blood traverses the landscape of the body

血液經由循環系統的管路

through the pipes of the circulatory system.

巡迴全身

In any plumbing system,

在任何水管系統

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

有許多因素可增加管壁的壓力

the properties of the fluid,

液體的特性

extra fluid,

過量的液體

or narrower pipes.

或者管路陝窄

So if the blood thickens,

如果血液變濃

a higher pressure is needed to push it, so the heart will pump harder.

就需要較高的壓力推送， 所以心臓就要更用力

A high-salt diet will lead to a similar result.

高鹽飲食也會導致類似的結果

The salt promotes water retention,

鹽能促進身體水份滯留

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

而過多的液體 會增加血容量和血壓

and stress, like the fight or flight response,

還有生活壓力 例如 ‘戰鬥或逃跑’ 的反應

releases hormones, like epinephrine and norepinephrine

身體會釋出賀爾蒙，例如 腎上腺素及去甲腎上腺素等

that constrict key vessels,

會使主要血管收缩

increasing the resistance to flow and raising the pressure upstream.

增加血流阻力 使上游血壓上升

Blood vessels can usually handle these fluctuations easily.

通常血管都能輕易地 應付這些變動

Elastic fibers embedded in their walls make them resilient,

血管壁的彈性纖維 使血管具有回彈能力

but if your blood pressure regularly rises above about 140 over 90,

但如果血壓常常超過140 /90

what we call hypertension, and stays there,

這就是高血壓 如果繼續下去

it can cause serious problems.

便會引起嚴重問題

That's because the extra strain on the arterial wall

因為動脈管壁承受過多壓力

can produce small tears.

便會出現細微的皸裂

When the injured tissue swells up,

這些損傷的組織腫脹時

substances that respond to the inflammation,

對發炎產生反應的物質

like white blood cells, collect around the tears.

例如白血球聚集在皸裂的地方

Fat and cholesterol floating in the blood latch on, too,

漂浮在血液中的 脂肪和膽固醇也會黏住

eventually building up to form a plaque

最後沉積形成斑塊

that stiffens and thickens the inner arterial wall.

使動脈壁內層變硬增厚

This condition is called atherosclerosis,

這種情況叫做動脈硬化

and it can have dangerous consequences.

會有危險的後果

If the plaque ruptures, a blood clot forms on top of the tear,

如果班塊破裂血栓 會在皸裂處形成

clogging the already narrowed pipe.

阻塞原來已經陝窄的血管

If the clot is big enough,

如果血栓夠大

it can completely block the flow of oxygen and nutrients to cells downstream.

便完全阻塞血液運送 氧氣和養份到下游的細胞

In vessels that feed the heart,

如果發生在營養心贜的血管

that will cause a heart attack,

這樣會導致心臟病發作

when oxygen-deprived cardiac muscle cells start to die.

心贜肌肉細胞缺氧而死亡

If the clot cuts off blood flow to the brain,

如果血栓阻斷血液流入腦部

it causes a stroke.

會造成腦中風

Dangerously clogged blood vessels can be widened

嚴重阻塞的血管

by a procedure called an angioplasty.

可經由“血管整型術 (血管擴張術)”打通

There, doctors thread a wire through the vessel

醫生將一根導線穿入血管

to the obstructed site,

到達阻塞部位

and then place a deflated balloon catheter over the wire.

然後在導線上 穿一支未充氣的氣球導管

When the balloon is inflated, it forces the passageway open again.

當氣球充氣時 血管便能再度打通

Sometimes a rigid tube called a stent

有時醫生會將稱為“支架”的硬管

is placed in a vessel to held hold it open,

植入血管以保持其暢通

letting the blood flow freely

使血流通行無阻

to replenish the oxygen-starved cells downstream.

使下游缺氧的細胞得到補充

Staying flexible under pressure is a tough job for arteries.

動脈在壓力下保持彈性 是件不容易的事

The fluid they pump is composed of substances

自心臟泵出的液體含有

that can get sticky and clog them,

能變黏稠而使之阻塞的物質

and your typical healthy heart beats about 70 times a minute,

一個健康的心臟 大約每分鐘跳70次

and at least 2.5 billion times during an average lifetime.

平均一生心臟跳動最少25億次

That may sound like an insurmountable amount of pressure,

聽起來這似乎是一種 大到難以承受的壓力

but don't worry, your arteries are well suited for the challenge.

但不要擔心，你的動脈 生來就是為了應付這種挑戰