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Chambers of the Heart
As we know, the heart is composed of 4 chambers where blood travels through to be pumped to the lungs and body.
- Right Atrium
- Right Ventricle
- Left Atrium
- Left Ventricle
Image 9: Diagram of the Human Heart
Open larger version of Image 9 here.
Valves of the Heart
Here you see an image showing the 4 valves of the heart. They function to maintain a one-way direction of blood flow.
- Atrioventricular (AV) Valves – those valves found between the atria and ventricles
- Tricuspid Valve – on the right side of the heart
- Mitral Valve – on the left side of the heart
- Semilunar Valves – those valves at the top of the heart
- Pulmonary Valve – on the right side of the heart
- Aortic Valve – on the left side of the heart
Image 10: Heart Valves
Open larger version of Image 10 here.
Check your understanding...
Which 2 chambers are found at the top of the heart (or superior)?
What are the names of the 4 chambers of the heart?
Which valve prevents blood from back-flowing into the left atrium?
Can you identify the number representing the right atrium in the diagram below (Image 11)?
Image 11: Heart Valves
Open larger version of Image 11 here.
Cardiac Cycles
The muscular contractions of the heart occur in repeating sequences of mechanical and electrical events. This repeating sequence is called a cardiac cycle, and this cycle can be divided into 2 phases:
- Systole Phase - period of contraction that the heart undergoes while it pumps blood into circulation
- Diastole Phase - period of relaxation that occurs as the chambers fill with blood
View The Amazing Heart (02:19) video as a review of blood flow during the cardiac cycle. DES login information.
Cardiac cycle details:
- When the heart beatsthe top chambers (atria) contract simultaneously, blood flows through open AV valves to fill the ventricles with blood.
- The AV valves close after blood is emptied from the atria (ventricular diastole phase).
- The bottom chambers (ventricles) are filled with blood and contract simultaneously, and blood flows out to the lungs and body through open semilunar valves (ventricular systole phase).
- The semilunar valves close after blood is emptied from the ventricles.
The cardiac cycle repeats at a resting adult heart rate of 60-80 beats per minute. Open Cardiac Cycle animation to see this process.
Image 12: The Cardiac Cycle
Open larger version of Image 12 here.
Sounds of a Heartbeat
The heart makes sounds as it beats and these sounds can be heard using an instrument called a stethoscope (seen in the image below).
Image 13: A doctor listening to a baby's heartbeat with a stethoscope.
Listening to the heart for sounds with a stethoscope is called auscultation. The sounds it makes are a "Lub-Dub. These sounds are caused form the turbulent blood flow and closing of the heart valves.
- The "Lub" occurs when the tricuspid and mitral valves close.
- The "Dub" occurs when the pulmonary and aortic valves close.
Now, let's listen to heart sounds that are normal and abnormal.
Abnormal heart sounds - a murmur
- You will hear a "swooshing" sound. The "swooshing" sound is caused by turbulent blood back-flowing through a valve. In this case, it is the mitral valve.
- You can learn more about heart valve problems at the American Heart Association website.
Check your understanding...
The cardiac cycle consists of a distinct relaxation and contraction phase. Which term is typically used to refer to ventricular contraction? Systole or Diastole
What is missing in the concept map below of the cardiac cycle (image below)?
Image 14: The Cardiac Cycle with parts missing
Open larger version of Image 14 here.
What produces the "dub" sound when auscultating the heart?
What can cause the "swooshing" abnormal heart sound of a murmur as heard in this lesson?
