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The Heart
Unit 3
What is the purpose of the heart?
• The heart is a hollow muscle that
pumps blood throughout the blood vessels by
repeated, rhythmic contractions.
Facts about the human heart
• The human heart pumps around 70 times per
minute, every minute of every day until we die!
• It must pump fluid through 160 000 km of
vessels.
• It must pump in two directions at once, without
mixing the fluid travelling in the two directions.
Video: A real heart beating
http://www.youtube.com/watch?v
=Gnv54V8Jj1U
Video: How the heart works
http://www.youtube.com/watch?v=oHMmtqKgs50
Structure of the Heart
• The heart of a mammal is divided into four
chambers.
1.
2.
3.
4.
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
Parts of the Heart
• Aorta: This is the largest
blood vessel in the body and
leads directly from the heart.
It mostly carries oxygenated
blood
• Pulmonary Artery: carries deoxygenated
blood from the heart to the lungs to be
oxygenated
• Pulmonary Vein: returns oxygenated blood
from the lungs to the heart to be pumped to
the rest of the body
• Pulmonary
circulation
• Atria: where blood enters the heart
(located on the top of the heart)
• Ventricle: where blood exits the heart
(located on the bottom of the heart)
• Septum: a wall that separates the left and
right sides of the heart
• Vena Cava: This is the largest vein in the body
that carries deoxygenated blood back to the
heart.
It is divided into two parts:
• Superior Vena Cava: Returns blood from the
upper portions of the body.
• Inferior Vena Cava: Returns blood from the lower
portions of the body.
• Bicuspid Valve: prevents blood from flowing
the wrong way in the heart. It is found
between the left atrium and left ventricle. It
has 2 cusps (parts).
• Tricuspid Valve: prevents blood from flowing
the wrong way in the heart. It is found
between the right atrium and right ventricle. It
has 3 cusps.
Both of these valves are called atrioventricular
valves (AV valves) because the divide the atria
and ventricles
• Semilunar valve: prevents blood from being
sucked back into the heart.
There are two of semilunar valves in the heart.
One is located between the aorta and left
ventricle the other is between the right ventricle
and the pulmonary artery
When you listen to you heart with a stethoscope,
the lub-dup sound you hear are the valves opening
and closing
How does blood flow through the heart?
1. Blood from the body enters the heart from
the vena cava. The super vena cava collects
blood from the upper body and the inferior
vena cava collects blood from the lower
body.
2. The vena cava carry blood to the right
atrium.
3. The atria contract, forcing the blood into the
right ventricle.
4. The ventricles contract. The blood is forced
out of the heart into the pulmonary artery.
5. The pulmonary arteries take the blood to the
lungs where it receives oxygen.
6. Upon exiting the lungs, the blood flows back
to the heart in the pulmonary veins.
7. The oxygenated blood collects in the left
atrium.
8. Again, the atria contract and the blood move
into the left ventricle.
9. The ventricles contract and the left ventricle
pumps the blood out of the heart through the
aorta to reach the body’s tissues.
Trace the pathway of blood
through the heart
Videos: Blood flow through the heart
http://www.youtube.com/watch?v=
FCimR_P9ID0
http://www.youtube.com/watch?v
=Rj_qD0SEGGk