Page 1 - 3. The heart- Structure

SAI International School

Subject- Biology, Class-VII
Topic- Transportation and Excretion
Subtopic- The structure of Human Heart
Lesson Notes

STRUCTURE OF HEART-

External structure-
• The human heart is about the size of a human fist.
• Known as the pumping organ.
• Located in the chest cavity.
• The lower end is slightly tilted towards the left.
• The heart is made of special muscles called the cardiac muscles.
• It beats 60-80 times per min.

• The heart is a muscular organ covered by a double membrane called pericardium.
• The pericardial fluid of the pericardium lubricates the heart.

INTERNAL STRUCTURE OF HUMAN HEART

• The heart is divided into four chambers so that the oxygenated and deoxygenated blood
does not mix.
• The upper two chambers of the heart are called atria - left atrium and right atrium
• The lower two chambers of the heart are called ventricles -
left ventricle and right ventricle
• A muscular septum separates the left and right side of a human heart

• The opening between the right atrium and right ventricle and left atrium and left
ventricle is guarded by valves.
• Valves prevent backflow of blood.

ROLE OF HEART
• The right side of the heart contains deoxygenated blood, which is received from all parts
of the body. The deoxygenated blood is pumped to the lungs. In lungs, the blood gets rid

of carbon dioxide and takes in oxygen from the air inhaled into them. This oxygen-rich
blood is received by the left side of the heart from lungs and is pumped to all parts of
the body.

Know More
Your heart can beat for several minutes outside of the body, until it runs out of energy. This is
because it produces its own electrical signals.