Lub Dub | Circulatory system physiology | NCLEX-RN | Khan Academy

Summary

This script delves into the heart's sounds, 'lub dub,' by explaining the role of its four valves in blood flow. It illustrates how the tricuspid and mitral valves open to fill the ventricles, while the pulmonary and aortic valves close to prevent backflow. The 'lub' sound corresponds to the closure of the former valves, and 'dub' to the latter, marking the transition from systole, when blood is pumped out, to diastole, the filling phase. The explanation simplifies the complex mechanics of the heart into an engaging rhythmic pattern.

Takeaways

• 👂 The heart makes sounds that are typically described as 'lub dub, lub dub, lub dub'.
• 🔍 The 'lub dub' sound can be spelled out as L-U-B, D-U-B, which repeats in a cycle.
• 📚 A diagram of the heart with exaggerated valves helps explain the origin of these sounds.
• 🔑 The heart has four valves: tricuspid (T), pulmonary (P), mitral, and aortic, which play a key role in the heart sounds.
• 💧 Blood flow through the heart is continuous, with simultaneous filling of the right and left ventricles.
• 🚫 Valves prevent backflow of blood by closing when blood tries to move in the wrong direction.
• 📉 The 'lub' sound corresponds to the closure of the tricuspid and mitral valves, also known as the first heart sound (S1).
• 📈 The 'dub' sound is associated with the closure of the pulmonary and aortic valves, known as the second heart sound (S2).
• 🔄 The opening and closing of these valves create a rhythmic cycle of sounds that can be heard and timed.
• 🕒 The time between 'lub' and 'dub' represents systole, when blood is being pumped out of the heart.
• ⏸ The period between 'dub' and the next 'lub' is diastole, when the heart is refilling with blood from the atriums.

Q & A

What are the typical sounds produced by the heart?

The typical sounds produced by the heart are 'lub dub, lub dub, lub dub', which is often represented by the letters L-U-B, D-U-B.

What is the purpose of the heart valves?

The heart valves, including the tricuspid, pulmonary, mitral, and aortic valves, regulate the flow of blood through the heart, ensuring it moves in the correct direction and preventing backflow.

How does the heart's anatomy relate to the 'lub dub' sounds?

The 'lub dub' sounds are associated with the opening and closing of the heart valves. 'Lub' corresponds to the closure of the tricuspid and mitral valves, while 'dub' is the sound made by the closure of the pulmonary and aortic valves.

What is the term for the first heart sound?

The first heart sound is also known as 'S1' and is produced by the closure of the tricuspid and mitral valves.

What is the term for the second heart sound?

The second heart sound is referred to as 'S2' and is produced by the closure of the pulmonary and aortic valves.

What happens during the period between 'lub' and 'dub'?

During the period between 'lub' and 'dub', the ventricles are ejecting blood into the arteries, a phase known as systole.

What is the phase called when blood is refilling from the atriums into the ventricles?

The phase when blood is refilling from the atriums into the ventricles is called diastole.

How can one differentiate between systole and diastole by listening to the heart sounds?

By listening to the heart sounds, systole can be identified by the period when blood is being squeezed out between 'lub' and 'dub', while diastole is the period of refilling, occurring between 'dub' and the next 'lub'.

Why do the heart valves close with a sound?

The heart valves close with a sound because of the sudden stop of blood flow when the valves snap shut to prevent backflow, creating the audible 'lub' and 'dub' sounds.

What is the significance of the black and white arrows in the explanation?

The black arrows represent incorrect or backward flow of blood, which the valves prevent. The white arrows indicate the correct flow of blood through the heart.

Outlines

00:00

💓 Understanding Heart Sounds and Valves

This paragraph explains the sounds our heart makes, typically described as 'lub dub', and how they relate to the heart's structure and function. It introduces a diagram of the heart with exaggerated valves to visually aid in understanding. The heart's chambers are labeled, and the flow of blood through them is described, including the simultaneous filling of the right and left ventricles. The paragraph details the role of the heart's valves—tricuspid (T), pulmonary (P), mitral, and aortic—in allowing blood flow in the correct direction and preventing backflow, with the closing of these valves producing the 'lub' and 'dub' sounds.

05:00

🔊 Heart Sounds and the Cardiac Cycle

The second paragraph delves into the specifics of the heart sounds, 'lub' and 'dub', correlating them with the closing of the tricuspid and mitral valves (S1) and the pulmonic and aortic valves (S2), respectively. It describes the cardiac cycle, distinguishing between systole, when the ventricles contract and eject blood, and diastole, when the ventricles are filling with blood from the atria. The summary explains how the timing of these sounds can indicate the phase of the cardiac cycle a listener is observing, with 'lub' marking the beginning of systole and the pause before the next 'lub' indicating diastole.

Keywords

💡lub dub

The 'lub dub' sounds are the characteristic noises made by the heart as it beats. These sounds represent the closing of heart valves: 'lub' (or S1) occurs when the tricuspid and mitral valves close, and 'dub' (or S2) occurs when the aortic and pulmonic valves close. This cyclical pattern is essential for understanding the cardiac cycle.

💡tricuspid valve

The tricuspid valve is one of the four main valves in the heart, located between the right atrium and the right ventricle. It opens to allow blood to flow from the right atrium to the right ventricle and closes to prevent backflow. In the video, its closure contributes to the 'lub' sound.

💡mitral valve

The mitral valve, also known as the bicuspid valve, separates the left atrium from the left ventricle. It opens to let blood flow from the left atrium into the left ventricle and closes to prevent backflow. Its closure, along with the tricuspid valve, produces the 'lub' sound.

💡aortic valve

The aortic valve is located between the left ventricle and the aorta. It opens to allow blood to flow from the left ventricle into the aorta and closes to prevent blood from flowing back into the heart. The closure of the aortic valve creates the 'dub' sound.

💡pulmonary valve

The pulmonary valve is situated between the right ventricle and the pulmonary artery. It opens to permit blood to flow from the right ventricle into the pulmonary artery and closes to stop the blood from returning to the heart. Its closure, along with the aortic valve, produces the 'dub' sound.

💡S1

S1, or the first heart sound, corresponds to the 'lub' sound. It is produced by the closing of the tricuspid and mitral valves at the beginning of ventricular contraction (systole). This sound signifies the start of the heart's pumping action.

💡S2

S2, or the second heart sound, corresponds to the 'dub' sound. It is generated by the closing of the aortic and pulmonary valves at the end of ventricular contraction (systole). This sound marks the end of the heart's pumping phase.

💡systole

Systole is the phase of the cardiac cycle when the heart's ventricles contract, pushing blood out into the arteries. The period between S1 (lub) and S2 (dub) is known as systole. During this time, blood is being pumped to the body and lungs.

💡diastole

Diastole is the phase of the cardiac cycle when the heart's ventricles relax and fill with blood from the atria. The period between S2 (dub) and the next S1 (lub) is known as diastole. This phase allows the heart to refill with blood for the next cycle of pumping.

💡backflow

Backflow refers to the reverse flow of blood within the heart, which can occur if valves do not close properly. In the video, backflow is depicted by black arrows indicating incorrect blood flow direction. Proper valve function prevents backflow and ensures efficient circulation.

Highlights

The heart makes distinct 'lub dub' sounds, which can be spelled out phonetically as L-U-B, D-U-B.

A diagram of the heart with exaggerated valves is used to explain the origin of heart sounds.

Blood flow through the heart is described, including the simultaneous filling of the right and left ventricles.

The tricuspid (T) and pulmonary (P) valves are labeled, along with the mitral and aortic valves.

Valves prevent backflow of blood by closing in response to incorrect flow direction.

The tricuspid and mitral valves are open when blood is in the ventricles, allowing correct blood flow.

When the ventricles contract, the aortic and pulmonary valves open to direct blood flow.

Backflow of blood is prevented by the closing of the aortic and pulmonary valves.

The 'lub' sound (S1) is associated with the closure of the tricuspid and mitral valves.

The 'dub' sound (S2) is produced by the closure of the pulmonary and aortic valves.

The timing of heart sounds can indicate whether the heart is in systole (contracting) or diastole (filling).

A full cycle of heart sounds includes both S1 and S2, with the time between indicating systole and diastole.

The heart's rhythmic valve movements create a pattern of sounds that can be used to understand its function.

The explanation of heart sounds provides insights into the mechanics of blood flow within the heart.

Understanding the 'lub dub' sounds can help in diagnosing heart conditions by listening to these rhythmic patterns.

The relationship between heart sounds and valve function is crucial for maintaining proper blood circulation.

The educational approach of using visual aids and sound associations makes the complex heart mechanism more accessible.

Transcripts

If you take a good long listen to your heart,

you'll actually notice that it makes sounds.

And those sounds are usually described

as lub dub, lub dub, lub dub.

And if you actually try to figure out

what that would spell out like, usually it's

something L- U- B, D- U- B. And it just repeats over and over

and over.

And to sort of figure out where those sounds come from,

what I did is I took that diagram of the heart

that we've been using and actually exaggerated

the valves, made them really, really

clear to see in this picture.

And we'll use those valves to kind of talk

through where those sounds are coming from.

So let's start by labeling our heart.

So we've got at the top, blood is coming into the right atrium

and going to the right ventricle.

It goes off to the lungs, comes back

into the left atrium and then the left ventricle.

So these are the chambers of our heart.

Now, keep your eye on the valves.

And we'll actually talk about them

as the blood moves through.

So let's start with blood going from the right atrium this way

into the right ventricle.

Now, at the same moment that blood is actually

going from the right atrium to the right ventricle,

blood is actually also going from the left atrium

to the left ventricle.

Now, you might think, well, how's that possible?

How can blood be in two places at one time?

But now remember that blood is constantly

moving through the heart.

So in a previous cycle, you actually

had some blood that was coming back from the lungs,

and that's what's dumping into the left ventricle.

And in a new cycle, you have a bit of blood

that's going from the right atrium to the right ventricle.

So you have simultaneously two chambers

that are full of blood-- the right and left ventricle.

Now, to get the blood into those ventricles,

the valves had to open.

And specifically, let's label all the valves now.

So here you have our tricuspid valve,

and I'm going to label that as just a T.

And then up here, you have the pulmonary valve,

and this'll be just a P. And on the other side,

you've got the mitral valve, which separates the left atrium

from the left ventricle.

And you've got the aortic valve.

So these are the four valves of the heart.

And as the blood is now in the ventricles,

you can see that the tricuspid and the mitral valve are open.

So far, so good.

Now, I've actually drawn the pulmonary valve as being open.

But is that really the case?

And the answer is no, because what happens

is that as blood is moving down from the right atrium

to the right ventricle, let's say that--

and I'm going to draw it in black.

Black arrows represent the bad or the wrong direction of flow.

So let's say some blood is actually

trying to go that way, which is not the way it should be going.

What happens is that these two valves, they,

based on their shape, are actually

not-- they're going to jam up.

They're going to basically just jam up like this,

and they're not going to let the blood pass through.

So this is what happens as that valve closes down.

And the same thing happens on this side.

Let's imagine you have some backwards flow of blood

by accident, meaning that it's going in the wrong direction.

Well, then these valves are going to close down.

So the white arrows represent the correct flow of blood,

and the black arrows represent the incorrect flow of blood.

So these valves shut down like that.

So now you can see how the valves,

the aortic and pulmonary valve, are actually

closed when the mitral and tricuspid valve are open.

So what happens after this?

So now our ventricles are full of blood, right?

They're full of blood.

And let's say they squeeze down, and they jettison all the blood

into those arteries.

Well, now you're going to have-- this is actually

going to close down.

Let's say this arrow flips around.

These arrows become white, because the direction of flow

is going to be in the direction we want it.

It's going to go this way and this way

And to allow that, of course, I need

to show you that these open up.

And they allow the blood to go the way that we want it to go,

so now blood is going to flow through those two valves.

But similar to before, you could have some backflow here.

You could have backflow here.

And you can have backflow here.

So you can imagine now, let's say

you have a little bit of backflow that

wants to go this way, which is the wrong direction.

Right?

Well, then these valves are going to close up.

They're going to say, no, you can't go that way.

They're going to close right up, and they're

going to not allow blood to go that way.

So this is going to happen on both sides, both ventricles.

And the valves shut.

And so basically the backflow of blood

is not allowed, because the valves keep shutting.

And when the valves snap shut-- so for example, right now

the tricuspid valve and the mitral valve snapped shut.

Well, that makes a noise.

So when T and M snap shut, that makes a noise that we call lub.

That's that first noise, that first heart sound.

In fact, sometimes people don't even call it lub dub.

They say, well, it's the first heart sound.

And to make that even shorter, sometimes people call that S1.

So if you hear S1, you know they're

talking about that same exact thing.

And this dub is called the second heart sound.

And, no surprise, just as before, if that's S1,

this is S2.

So you'll hear S1 when the tricuspid and mitral valve

snap shut.

So far, so good.

But you also know that if that's what's making noise,

you can kind of guess-- and it's a very smart guess-- that

at the same time, the pulmonic valve and the aortic valve

just opened.

So if the other valves snap shut, these just opened.

Right?

You can kind of assume that, although the noise

you're hearing is actually from here.

So what's happening with dub?

Well, the opposite.

And what I mean by that is-- let me now

show you what happens a moment later.

Well, after the ventricles are done squeezing,

then we get to a point where you might

have a little bit of flow that way and that way,

just as I drew before.

And these valves snap shut as well.

So now these snap shut.

And as these snap shut-- because they

don't want to allow backflow, right?

They're going to snap shut like that.

They make noise.

And so when you have dub, you actually

have noise coming from the pulmonic and aortic valve

snapping shut.

And that must mean that then the other two valves just opened

up-- the tricuspid and mitral just opened.

You can assume that, right?

And I didn't draw that in the picture.

Let me update my picture now to show that.

So now these two have opened up, and blood

is coming into the ventricles again.

So it's actually a nice little rhythm that you get going.

And every time these valves go open and shut, you hear noise.

So you can kind of figure out what's happening based on--

and these actually-- let me erase that.

And now you have white arrows going this way.

And we've returned to where we started from.

So you basically have a full cycle,

and between these two-- so let's say from lub to dub,

because there's a little bit of space there.

If you were to follow it over time, over time,

this is what it might look like if this is a little timeline.

You might hear lub here, or the first heart sound.

I'll just call it S1.

And you might hear S2 here, the second heart sound.

And then you'll hear S1 again over here and S2.

And what's happening between the two-- so between these two,

this time lag here-- is that blood is actually

squeezing out, because the pulmonary and aortic valves

just opened.

It is squeezing out and going out to the whole body.

So this is when blood is going to the body,

and sometimes we call that systole.

And between dub and the next lub-- so

in this area right here-- well, at that point,

blood is kind of refilling from the atriums

into the ventricles, and we call that diastole.

So now you can actually listen to your heart.

And you can actually figure out, well,

if you're listening to the sound between lub and dub

or the space in time between lub and dub,

that's when you're having systole.

And if you're listening to or waiting for the sound

to start up again-- so you just heard dub,

and you're waiting for lub again-- then that space in time

is diastole.