How blood pressure works - Wilfred Manzano

翻译人员: Yuanqing Edberg 校对人员: Sue Chen

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

如果把你身体内的血管都排成一条，

they'd be 95,000 kilometers long

它们有95，000 千米那么长。

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

每天，它们携带7，500升血液，

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

虽然那实际上是四到五升一遍一遍的重新循环，

delivering oxygen, and precious nutrients

以传递氧气和珍贵的营养，

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

比如葡萄糖，氨基酸等到身体的组织。

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

这些血液加在一起， 对血管壁施加了一种强力。

That force is called blood pressure,

那种力量就叫做血压。

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

血压随着心跳升高或降低。

It's highest during systole,

血压在心脏收缩的时候是最高的。

when the heart contracts to force blood through the arteries.

当心脏收缩迫使血液通过动脉。

This is your systolic blood pressure.

这就是你的收缩压。

When the heart is at rest between beats,

当心脏在跳动间歇期间，

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

血压降到最低的数值，这就是舒张压。

A typical healthy individual produces a systolic pressure

典型的健康的个体的收缩压

between 90 and 120 millimeters of mercury,

在90到120 毫米汞柱之间，

and diastolic pressure between 60 and 80.

舒张压在60到80之间。

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

两者合在一起，正常的读数是 介于80到120.

The blood traverses the landscape of the body

血液穿过整个身体，

through the pipes of the circulatory system.

是通过循环系统的血管。

In any plumbing system,

在任何液流系统，

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

都会有几项因素使管壁受压增高：

the properties of the fluid,

液体的特性，

extra fluid,

多余的液体，

or narrower pipes.

或狭窄的管腔。

So if the blood thickens,

如果血液变得粘稠，

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

血压需要升高来把它推送出去， 那么心脏会跳得更厉害。

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

高盐饮食会导致类似的症状。

The salt promotes water retention,

盐促进水潴留，

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

额外的液体增加了血容量和血压，

and stress, like the fight or flight response,

还有压力， 比如搏斗或搏斗似的反应，

releases hormones, like epinephrine and norepinephrine

会释放荷尔蒙，如肾上腺素 或去甲肾上腺素

that constrict key vessels,

它们能收缩主要的血管，

increasing the resistance to flow and raising the pressure upstream.

增加流动的阻力并且升高血压。

Blood vessels can usually handle these fluctuations easily.

血管通常能够很容易地处理这样的波动。

Elastic fibers embedded in their walls make them resilient,

血管壁里的弹性纤维使得血管富有弹性，

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

但是你的血压增高多余140/90，

what we call hypertension, and stays there,

我们就把它叫做高血压，如果一直持续，

it can cause serious problems.

可引起严重的问题。

That's because the extra strain on the arterial wall

那是因为额外的血管壁 的压力

can produce small tears.

能引起很小的泪泡，

When the injured tissue swells up,

当受伤的组织肿胀起来，

substances that respond to the inflammation,

炎症反应的物质，

like white blood cells, collect around the tears.

如白细胞会聚集在泪泡周围。

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

脂肪和胆固醇在血液中漂浮，停留，

eventually building up to form a plaque

最终会形成粥样块状物

that stiffens and thickens the inner arterial wall.

使得动脉血管内壁僵硬和变厚。

This condition is called atherosclerosis,

这种情况就叫做动脉粥样硬化，

and it can have dangerous consequences.

这能产生危险的后果。

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

如果粥样块状物破裂， 血块在已成形的块状物顶部成型

clogging the already narrowed pipe.

堵住已经狭窄的管腔。

If the clot is big enough,

如果血块够大，

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

它能够堵住氧分和营养 传送到下面的细胞

In vessels that feed the heart,

当这发生在心脏血管中，

that will cause a heart attack,

就会引起心肌梗塞，

when oxygen-deprived cardiac muscle cells start to die.

没有氧分的时候心肌细胞开始死亡。

If the clot cuts off blood flow to the brain,

如果栓塞堵住了大脑的血流，

it causes a stroke.

就引起了中风。

Dangerously clogged blood vessels can be widened

危险的栓塞血管可以

by a procedure called an angioplasty.

被通过血管成形术的手术扩大。

There, doctors thread a wire through the vessel

医生在血管中放置一条细管

to the obstructed site,

到栓塞的地方，

and then place a deflated balloon catheter over the wire.

然后在细管上放置一个未充气的气球导管

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

当气球充气的时候，它会强迫同道再次打开。

Sometimes a rigid tube called a stent

有时一条硬性管道叫做支架

is placed in a vessel to held hold it open,

会放入血管使其张开，

letting the blood flow freely

让血液自由地流动

to replenish the oxygen-starved cells downstream.

来补充下面管道里缺氧的细胞。

Staying flexible under pressure is a tough job for arteries.

在压力下保持弹性对动脉是一种艰难的工作。

The fluid they pump is composed of substances

它们泵出的液体是由一些

that can get sticky and clog them,

能够粘连并堵住它们的物质组成，

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

通常你的心跳在70次每分钟，

and at least 2.5 billion times during an average lifetime.

在平均寿命中至少跳上250亿次

That may sound like an insurmountable amount of pressure,

这听起来像不可逾越的一堆压量，

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

但是别担心，你的动脉为此挑战而装备完好。