Introduction
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The heart pumps blood
Blood vessels provide the conduits within
which blood circulates to all body tissues
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Main function:
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◦ Transportation
The main organ of the
circulatory system
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Location and Size
Coverings and Wall
Chambers
Valves
Page 329 in book
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The relative size and
weight of the heart give
a few hints to the
incredible strength the
heart has
Size:
◦ approx. size of fist
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Shape:
◦ Hollow, Cone-shaped
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Weight:
◦ Less than a pound
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Apex points toward the left hip and rests on the
diaphragm
◦ Approx. where the left intercoastal space is
 Where you would place a stethoscope to hear the heart beats
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Base – broader posterosuperior aspect, from where the
great vessels of the body emerge, points toward the
right shoulder and lies beneath the 2nd rib
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Pericardium:
◦ double sac of serous membrane
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The thin visceral pericardium, or epicardium tightly hugs the
external surface of the heart and part of the heart wall
A lot of connective tissue
There is a fibrous layer helps protect the heart and anchors it to
surrounding structures such as the diaphragm and the sternum
A slippery lubricating fluid (serious fluid) is produced by the
pericardial membranes
◦ The fluid allows the heart to beat easily in a relatively frictionless
environment as the pericardial layers slide smoothly across each other
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Myocardium:
◦ Consists of think bundles of cardiac muscle twisted around and actually
contracts
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Endocardium:
◦ Thin, glistening sheet of endothelium that lines the heart chambers
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Two atria
Two ventricles
Each of these is lined with endocardium, which helps blood
flow smoothly through the heart
The superior atria are typically the receiving chambers
◦ They are not important in the actual pumping activity
◦ Blood flows into the atria under low pressure from the veins of the
body and then continues to fill the ventricles
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The inferior, thick-walled ventricles are the discharging
chambers, or actual pumps of the heart
Video
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Read information on page 331-332
Cardiac Circulation/ Operation
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Circulation Song
Pg 333
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1. Once the deoxygenated red blood cell (RBC) returns to the heart, it enters either
through the superior vana cava or the inferior vena cava. The superior vena cava
returns deoxygenated blood from the upper part of the body to the heart. The inferior
vena cava returns deoxygenated blood from the lower part of the body to the heart.
These large veins lead into the right atrium.
2. The RBC passes through the tricuspid valve into the right ventricle.
3. The RBC is then pumped through the pulmonary valve into the pulmonary artery
and on to the lungs. There the RBC gives off carbon dioxide and picks up oxygen.
4. The RBC returns to the heart through a pulmonary vein, enters the left atrium,
passes through the mitral valve, and flows into the left ventricle.
5. The left ventricle pumps the fully oxygenated RBC through the aortic valve, into
the aorta, the body's main artery, and out to the body.
6. From the aorta, the RBC flows into one of the many arteries of the body, through
the arterioles, and then to the capillaries, where the RBC will deliver oxygen and
nutrients to the cells and remove wastes and carbon dioxide. Next it moves through
the venules, veins, and on to the vena cava in a deoxygenated state, and returns to the
heart, only to begin its repetitive journey once again. This whole process has taken
approximately 20 seconds!
That single RBC will travel about 950 miles (more than 1500 kilometers) in its brief 4month lifetime!