Download The Heart - Interlake School Division

The Heart
The Heart
• The heart is a cone-shaped, muscular
organ about the size of a fist.
• It is located between the lungs directly
behind the sternum and is tilted so that the
apex (pointed end) is oriented to the left.
• It is really two pumps working side by
side
Chambers of the Heart
The heart has four chambers:
– Two upper, thin-walled chambers are
called atria (singular atrium).
• The atria receive blood.
• The right atrium receives blood from
the body via the superior vena cava.
• The left atrium receives blood from
the lungs via the pulmonary veins.
Chambers of the Heart
– Two lower, thick-walled chambers called
ventricles.
• Ventricles pump the blood.
• The right ventricle pumps blood to the
lungs via the pulmonary arteries.
• The left ventricle pumps blood to the
body via the aorta.
Chambers of the Heart
Composition of the Heart
• The heart is mostly made up of cardiac
muscle tissue known as myocardium.
• The heart lies within a thick, membranous
sac that secretes a small amount of
lubricating fluid. This sac is called the
pericardium.
• The inner surface of the heart is lined with
connective tissue and endothelial tissue.
This is known as the endocardium.
Valves of the Heart
• The heart has four valves which direct the
flow of blood and prevent its backward
movement.
– Two valves are found between the atria and
ventricles and are called atrioventricular
valves.
• The a.v. valve on the right side of the heart
is called the tricuspid valve because it has
three flaps or cusps.
• The a.v. valve on the left is called the
bicuspid (mitral) valve – it has 2 flaps.
Valves of the Heart
– Two valves are found between the ventricles
and their attached vessels. These are known
as the semi-lunar valves – their flaps
resemble half-moons.
• The pulmonary semilunar valve is found
between the right ventricle and the
pulmonary arteries. Blood is pumped
through this valve on its way to the lungs.
• The aortic semilunar valve is found
between the left ventricle and the aorta.
Blood is pumped through this valve on its
way to the body tissues.
• The valves of the
heart are supported
by strong fibrous
strings called chordae
tendinae.
Major Vessles
– The pulmonary arteries carry blood from the
heart to the lungs. Blood carried in this vessel
exits the heart from the right ventricle.
– The pulmonary veins carry oxygen rich blood
from the lungs to the heart. Blood from this
vessel enters the left atrium.
– The aorta carries blood from the heart to the
body tissues. Blood carried in this vessel
exits the heart from the left ventricle.
Passage of Blood through the
Heart
• Oxygen poor blood enters right atrium via
superior and inferior vena cava.
• Right atrium sends blood through the tricuspid
valve to the right ventricle.
• Right ventricle pumps blood though the
pulmonary semilunar valve into the pulmonary
arteries which go to the lungs.
• Blood becomes oxygenated in the lungs and
then enters the left atrium via the pulmonary
veins.
Passage of Blood through the
Heart
• Left atrium sends blood through the
bicuspid valve to the left ventricle.
• Left ventricle pumps blood through the
aortic semilunar valve into the aorta.
• The aorta delivers oxygen rich blood to the
body.