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How your heart works


Your heart

Your heart is a muscle and its job is to pump blood around the body.

  • It is about the size of your fist.
  • It is protected by your ribs and breastbone (sternum).
  • It beats about 100,000 times a day, pumping blood through your body.
  • Blood delivers essential oxygen and nutrients to every cell.
  • Blood also takes away waste products and carbon dioxide.

Your heart pumps blood through a network of arteries and veins.

  • Arteries carry oxygen-rich blood from the heart to the body.
  • Veins carry oxygen-poor blood back to your heart and lungs to start the cycle over again.

The heart itself also needs its own supply of oxygen-rich blood. The coronary arteries handle this job.  Coronary artery disease is when these arteries become narrowed or blocked so your heart does not get enough oxygen to function effectively.

Anatomy of the heart

Your heart is divided into four sections (or chambers):

  • Two at the top (upper chambers)
    • Called the left and right atria (atrium if it’s singular).
    • The atria receive blood from veins
  • Two at the bottom (lower chambers)
    • Called the left and right ventricles.
    • The right ventricle pumps blood from the heart to the lungs to pick up oxygen.
    • The left ventricle pumps the oxygen-rich blood through your entire body.

A muscular wall (the septum) separates the right side from the left.

The left and right chambers are connected by one way valves that open and close with every heartbeat. Valves ensure blood is pumped in the right direction.

How it works

To pump blood throughout the body, your heart pumps in two-stages.

  1. First it contracts.
  2. Then it relaxes

This action is similar to clenching and unclenching your fist.

This motion is controlled by an electrical signal that starts in the right atrium, at the sinoatrial node (SA Node). 

<p>How the blood flows through the heart</p><p> </p>

How the blood flows through the heart

 

The SA Node sends an electrical signal (impulse) through the atria, causing them to contract. 

The signal then travels to the Atrioventricular (AV Node), which is between the atria and the ventricles. The AV node holds the electrical signal for a moment.

  • As it does, the blood from the atria is pumped into the ventricles.

Then, the signal travels to the ventricles, making them contract.

  • This sends blood rushing to the lungs and the rest of your body.

The signal causes different parts of the heart to work together.  As one part contracts, the other relaxes. This creates a heartbeat with a regular rhythm.

If the signal is too slow or fast, or erratic, the heart can’t beat properly. This is called arrhythmia.

An electrocardiogram (ECG or EKG) is a test that helps to determine if there is a problem with your heart's electrical system. It measures electrical signals as line tracings on paper.

<p>The heart’s electrical system</p><p> </p>

The heart’s electrical system

 

What happens when your heart beats?

  1. Oxygen poor blood flows from your body (muscles, organs, brain and heart) into the right atrium. When it is full, the atrium contracts.
  2. When the atrium contracts, the valve between the right atrium and the right ventricle opens. The blood flows into the right ventricle.
  3. When the right ventricle is full it contracts and pumps the blood to the lungs.
  4. In the lungs, carbon dioxide is removed and fresh oxygen is added.
  5. The blood then flows into the left atrium.
  6. When the left atrium contracts, the valve between the left atrium and left ventricle opens.  The blood flows into the left ventricle.
  7. The left ventricle pumps the oxygen-rich blood into the aorta and out to the rest of your body.

With each beat of your heart, blood is pushed through your arteries. This is what creates your pulse.

Your heart rate (your pulse) is the number of times your heart beats per minute.  Normal heart rate varies from person to person. Knowing your heart rate can help you spot health problems. A normal adult resting heart rate is usually about 60 to 100 beats per minute.

  • Female hearts tend to beat faster than male hearts because they are slightly smaller
  • During rest, your heartbeat will slow down
  • With exercise, it can go faster.
Resources:

Web MD has an even more detailed explanation of how the heart works.


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