Name: 【TED-Ed】How the heart actually pumps blood - Edmond Hui
Uploaded: 2014-05-28T16:37:18.000Z
Duration: 4 min 28 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

humans had no idea what purpose the heart served.

In fact, the organ so confused Leonardo da Vinci,

Although everyone could feel their own heart beating,

it wasn't always clear what each thump was achieving.

because if a heart was exposed or taken out,

It's also impossible to see through the blood vessels,

making it difficult to see the heart valves working.

or animations that don't really show how it works.

It's as if there has been a centuries old conspiracy

to accept that heart function cannot be demonstrated.

is simply to cut it open and label the parts.

That way students might not fully grasp the way it works,

or potentially misleading statements like,

one with blood going to the lungs and back,

In reality, mammals have a figure-eight circulation.

Blood goes from one heart pump to the lungs,

back to the second heart pump, which sends it to the body,

because it marks two completely different morphologies.

thinking it signals an intimidating subject

compeltely understand how it all actually works.

That's when its functions become apparent

as medics get to observe the motion of the heart's valves.

So, let's imagine you're a medic for a day.

What you'll need to get started is a whole fresh heart,

and you'll see that it doesn't pump when squeezed by hand.

That's because water doesn't enter the heart cleanly enough

We can solve this problem in an extraordinarly simple way.

Simply identify the two atria and cut them off,

trimming them down to the tops of the ventricles.

This makes the heart look less complicated

because the atria have several incoming veins attached.

So without them there, the only vessels remaining

which rise like white columns from between the ventricles.

It looks -- and really is -- very simple.

If you run water into the right ventricle from a tap

(the left also works, but less spectacularly),

tries to close against the incoming stream.

Squeeze the ventricle and a stream of water

The ventricular valves, called the tricuspid in the right ventricle

as the ventricle is rhythmically squeezed.

This flow of water mimics the flow of blood in life.

You'll notice they don't leak at all when the ventricles are squeezed.

Over time, they also close against each other

which explains how this mechanism continues to work seamlessly

for more than 2 billion beats a heart gives in its lifetime.

Now, anyone studying the heart can hold one in their hands,

Understanding how this dependable inner pump works

gives new resonance to the feeling you get