血压是如何工作的 - Wilfred Manzano：英语精读讲义

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

如果把你体内所有的血管连起来，

they'd be 95,000 km long.

它们的长度会达到 9.5 万公里。

And every day, they carry the equivalent 短語搭配

它们每天输送的血液量，

of over 7,500 L of blood.

相当于超过 7500 升血液。

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

尽管这实际上只是那相同的 4 到 5 升血液

recycled over and over, 短語搭配

在不断地循环，

delivering oxygen and precious nutrients 短語搭配

将氧气和珍贵的营养物质，

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

如葡萄糖和氨基酸，输送到全身组织。

All that blood exerts a force 短語搭配

所有这些血液都会对

on the muscular walls of the blood vessels.

血管肌肉壁施加一种力量。

That force is called blood pressure,

这种力量被称为血压，

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

它会随着心跳的节奏而升高和降低。

It's highest during systole, 用詞

它在收缩期达到最高值，

when the heart contracts to force blood through the arteries.

此时心脏收缩，将血液挤压进动脉。

This is your systolic blood pressure.

这就是你的收缩压（高压）。

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

当心脏在两次跳动之间休息时，

blood pressure falls to its lowest value,

血压降到最低值，

the diastolic pressure. 用詞

即舒张压（低压）。

A typical healthy individual produces a systolic pressure

一个典型的健康个体的收缩压

between 90 and 120 mm of mercury 文化背景

在 90 到 120 毫米汞柱之间，

and diastolic pressure between 60 and 80.

而舒张压在 60 到 80 之间。

Taken together, a normal reading 表達脈絡

综合来看，正常的读数

is a bit less than 120 over 80. 用詞

会略低于 120/80。

The blood traverses the landscape of the body

血液穿越身体各个角落的途径，

through the pipes of the circulatory system. 表達脈絡

就是通过循环系统这些“管道”。

In any plumbing system,

在任何管道系统中，

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

有几个因素会增加管道壁承受的压力，

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

即流体特性、流体增多或管道变窄。

So if the blood thickens, 語法

因此，如果血液变稠，

a higher pressure is needed to push it,

就需要更高的压力来推动它，

so the heart will pump harder.

心脏就得更用力地泵血。

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

高盐饮食也会导致类似的结果。

The salt promotes water retention, 用詞

盐会促使体内水分潴留，

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

多余的水分会增加血容量并升高血压。

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

另外，压力，比如“战或逃”反应，

releases hormones like epinephrine and norepinephrine

会释放肾上腺素和去甲肾上腺素等激素，

that constrict key vessels, 用詞

使关键血管收缩，

increasing the resistance to flow 用詞

增加血流阻力，

and raising the pressure upstream. 用詞

并提高上游的血压。

Blood vessels can usually handle these fluctuations easily.

血管通常能轻松应对这些波动。

Elastic fibers embedded in their walls make them resilient.

血管壁内嵌的弹性纤维使其具有弹性。

But if your blood pressure regularly rises

但如果你的血压经常升高

above about 140 over 90,

到 140/90 以上，

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

也就是我们所说的高血压，并保持在这个水平，

it can cause serious problems.

就会引发严重的问题。

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

这是因为动脉壁承受的额外压力

can produce small tears.

会产生微小的撕裂。

When the injured tissue swells up, 短語動詞

当受损组织肿胀时，

substances that respond to the inflammation,

对炎症做出反应的物质，

like white blood cells, collect around the tears.

如白细胞，就会聚集在撕裂处周围。

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

血液中漂浮的脂肪和胆固醇也会附着上去，

eventually building up to form a plaque 短語動詞

最终堆积形成斑块，

that stiffens and thickens the inner arterial wall.

使动脉内壁变硬变厚。

This condition is called atherosclerosis, 用詞

这种情况被称为动脉粥样硬化，

and it can have dangerous consequences.

它可能会导致危险的后果。

If the plaque ruptures,

如果斑块破裂，

a blood clot forms on top of the tear,

撕裂处上方就会形成血栓，

clogging the already narrowed pipe. 表達脈絡

堵塞本已变窄的血管。

If the clot is big enough, 語法

如果血栓足够大，

it can completely block the flow of oxygen 短語搭配

它就能完全阻断氧气

and nutrients to cells downstream. 用詞

和营养物质流向下游细胞。

In vessels that feed the heart, 用詞

在为心脏供血的血管中，

that will cause a heart attack,

这会导致心脏病发作，

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

因为缺氧的心肌细胞会开始死亡。

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

如果血栓切断了流向大脑的血液，

it causes a stroke.

就会导致中风。

Dangerously clogged blood vessels can be widened

严重堵塞的血管可以通过

by a procedure called an angioplasty. 用詞

一种叫做“血管成形术”的手术来扩张。

There, doctors thread a wire through the vessel 用詞

在手术中，医生通过血管穿入一根导丝，

to the obstructed site,

一直到达堵塞部位，

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

然后沿着导丝送入一个未充气的球囊导管。

When the balloon is inflated,

当球囊充气时，

it forces the passageway open again. 短語搭配

它会强行将通道再次撑开。

Sometimes a rigid tube called a stent 用詞

有时也会在血管中放置一个

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

叫做“支架”的刚性管以帮助保持血管通畅，

letting the blood flow freely to replenish 用詞

让血液自由流动，以补充

the oxygen-starved cells downstream.

下游急需氧气的细胞。

Staying flexible under pressure 習語

在压力下保持柔韧性

is a tough job for arteries.

对动脉来说是一项艰巨的工作。

The fluid they pump is composed of substances 短語搭配

它们泵送的流体所包含的物质

that can get sticky and clog them. 用詞

可能会变得黏稠并堵塞血管。

And your typical healthy heart

而你那典型的健康心脏

beats about 70 times a minute

每分钟大约跳动 70 次，

and at least 2 and a half billion times

在平均一生中，

during an average lifetime.

至少会跳动 25 亿次。

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

这听起来像是一个无法承受的压力，

but don't worry.

但别担心。

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

你的动脉完全能够应对这个挑战。