Lub-dub

Doc - 15-02-2016, 19-31

Put two fingers on your wrist.
Just where you can see a faint blue line, that should work ok.
You might feel a beat against your fingers.
Can you feel it?
Well done! I’m proud to inform you that you are alive.

This might not be news to you, but how often do you think about the organ that keeps you alive? How well do you understand the pulsing that you feel in your chest?

Let me offer you a small insight into this non-stop involuntary process.

A bit of background knowledge-
Your heart is an organ made out of muscle, it is the approximate size of your fist and you can find it in the middle of your chest pointing slightly to the left.

It has four chambers as seen in the diagram below-

Doc - 15-02-2016, 19-45

So what is a heartbeat? Why does it happen?

Cells in your body need oxygen to do their thing- be it skin cells, nerve cells or muscle cells, they all need the oxygen which is taken up in your lungs.
But as you may have noticed, your lungs aren’t close enough to your body that the oxygen might just magically get passed on.
This is why blood exists. Blood carries the oxygen from the lungs to all other body parts that need the oxygen. It must keep moving around, so an organ is in place that pumps the blood to allow it to pass through your body at speed, preventing it from becoming static.
The heart is this pump.

Every time your heart beats, it undergoes contraction (known as systole) and relaxation (also called diastole).
One round of these two is one heartbeat, and it happens in approximately 0.8 seconds.
In this fraction of a second many things happen:

1. Atrial Systole: The left and right atrium (1a & 1b) become smaller as they contract. This allows the blood to fall through the AV valves and into the ventricles (2a & 2b).

2. Ventricular Systole: The sides of the ventricles contract inward, pushing the blood out of the ventricles through the valves and up into the arteries- the aorta on the left side and the pulmonary artery on the right.

3. Diastole: The heart relaxes, allowing for blood to reenter it in order to complete the cycle all over again.

Where does the famous lub-dub noise come from then?

Lub: AV valves that separate the atria from the ventricles exist to prevent blood from flowing back into the atria, so when the ventricles contract, these must close. The noise these make when they close is recognised as “lub”.

Dub: After blood has been pushed out of the heart, the valves at the opening of the main arteries must close so that blood doesn’t fall back into the heart. The sound these make as they close is described as “dub”.

So next time your heart interrupts your attempts to fall asleep, take a second to thank it too for its hard work.

-teresa-

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