Bell Work
What is the heart?
Where is it located?
What is the difference between an artery and a vein?
Can a vein's blood have more oxygen than an artery’s
What organ does the word pulmonary refer to?
What do the prefixes tri- and bi- mean?
What is a wall?
What is a chamber?
What is a valve?
The Heart
• How big is the heart?
– About the size of your fist and weighs less than a
– It is hollow and cone-shaped
• Where is the heart?
– The middle cavity of the thorax called the
mediastinum flanked by the lungs
• How is it positioned?
– The apex is directed toward the left hip and rests on
the diaphragm while the base points toward the
right shoulder and lies beneath the second rib.
The Heart Cover
• The heart is enclosed by a double sac of
serous membrane called the pericadium
• Epicardium or visceral pericardium – thin layer
that tightly hugs the external surface of the
heart and is considered to be a part of the
heart wall
• Parietal pericardium – loosely applied layer
that helps protect the heart while anchoring it
to surrounding structures.
The Heart Wall
• The heart wall is composed of three layers
– Epicardium – outer layer describe previously
– Myocardium – The layer that actually contracts. It
is composed of thick bundles of twisted cardiac
– Endocardium – layer of endothelium that lines the
inner chambers of the heart
The Chambers of the heart
• The heart has four chambers or cavities.
• Two superior atria (singular atrium) and two
inferior ventricles
• Atria – receiving chambers. Blood returns to
the heart through veins and fills the atria
under low pressure
• Ventricles – thick walled, discharging
chambers. When they contract, blood is
propelled out of the heart
• The right ventricle forms most of the anterior
heart and is used in the pulmonary circuit which
involve the lungs
• The left ventricle forms the apex and is used in
the systemic circuit involve the body
• Arteries carry blood away from the heart
• Veins carry blood toward the heart
• Systolic pressure – the pressure in the arteries at
the peak of ventricle contraction
• Diastolic pressure – the pressure when the
ventricles are relaxing
• The heart contains four valves to keep the blood
flowing in one direction.
• There are two artioventricular (AV) valves that are
located between the atria and ventricles. These
prevent a backflow from the ventricles back into the
• Left AV is called the bicuspid valve (has two flaps)
and the right AV is called the tricuspid (has three
flaps). They are anchored to the heart walls by
chordae tendineae and this prevents the valves
from flipping into the atria
The other two valves – the semilunar
• Pulmonary – prevents blood heading toward
the lungs to flow back into the heart
• Aortic – prevents blood heading toward the
body to flow back into the heart
• The semilunar valves are closed when the
heart is relaxed and are forced open when the
heart contracts, while the AV valves are open
when the heart is relaxed but are forced
closed when the heart contracts.
Cardiac Circulation
• Let us follow the blood as it returns from the
body and enters the heart
• Oxygen deprived blood approaches the heart
through the venae cavae (inferior and superior)
and enters into the right atrium
• Blood then fills the right ventricle as it passes by
the tricuspid valve.
• The right ventricle contracts, forcing the tricuspid
valve to close, the pulmonary semilunar valve to
be forced open, and the blood to travel the lungs
through the pulmonary arteries.
• The lungs recharge the blood with oxygen and the
blood returns to the heart.
• Oxygen rich blood returns to the heart using the
pulmonary veins and enter the left atrium.
• The blood flows past the open bicuspid valve into
the left ventricle.
• The left ventricle contracts forcing closed the
bicuspid valve, forces the aortic semilunar valve
open, and forces the blood out to the body via the
• The blood uses various arteries to reach all parts of
the body. Capillary beds are used for gas
exchanges, and the blood is brought back to the
heart via veins and the process repeats.
Review Game
• http://sciencereviewgames.com/srg/games/ps