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Transcript
The Heart
Function
• Transportation system by which oxygen and
nutrients reach the body's cells, and waste
materials are carried away.
• Also carries substances called hormones,
which control body processes, and antibodies
to fight invading germs.
Parts of the Circulatory System
• Divided into three major parts:
– The Heart
– The Blood
– The Blood Vessels
• Two parts
Circulation
• Heart acts as double pump
– Blood from the right side pump is dark red and low in
oxygen (oxygen-poor)
• Travels through pulmonary arteries to lungs where it gets
fresh oxygen and becomes bright red
– Blood from lungs through pulmonary veins back to
the heart's left side pump
• Pumped out into the body
3 Kinds of Circulation:
• Pulmonary circulation
– Movement of blood from the heart, to the lungs, and
back to the heart again
• Coronary circulation
– Movement of blood through the tissues of the heart
• Systemic circulation
– Supplies nourishment to all of the tissue located
throughout the body, except for the heart and lungs
The Heart’s Role in Blood Circulation
• Systemic circulation
– Blood flows from the left side of the heart
through the body tissues and back to the right
side of the heart
• Pulmonary circulation
– Blood flows from the right side of the heart to the
lungs and back to the left side of the heart
Cardiac Circulation
• Blood in the heart chambers does not nourish
the myocardium
• The heart has its own nourishing circulatory
system consisting of
– Coronary arteries—branch from the aorta to
supply the heart muscle with oxygenated blood
– Cardiac veins—drain the myocardium of blood
– Coronary sinus—a large vein on the posterior of
the heart, receives blood from cardiac veins
• Blood empties into the right atrium via the
coronary sinus
The Heart
• Location
– Thorax between the lungs in the inferior mediastinum
• Orientation
– Pointed apex directed toward left hip
– Base points toward right shoulder
• About the size of your fist
The Heart: Coverings
• Pericardium—a double-walled sac
– Fibrous pericardium is loose and superficial
– Serous membrane is deep to the fibrous
pericardium and composed of two layers
• Visceral pericardium
– Next to heart; also known as the epicardium
• Parietal pericardium
– Outside layer that lines the inner surface
of the fibrous pericardium
– Serous fluid fills the space between the layers of
pericardium
The Heart: Wall
• Three layers
– Epicardium
• Outside layer
• This layer is the
visceral
pericardium
• Connective tissue
layer
– Myocardium
• Middle layer
• Mostly cardiac
muscle
– Endocardium
• Inner layer
• Endothelium
The Heart: Chambers
• Right and left side act as separate pumps
• Four chambers
– Atria
• Receiving (top) chambers
– Right atrium
– Left atrium
– Ventricles
• Discharging (bottom) chambers
– Right ventricle
– Left ventricle
The Heart: Septum
• Interventricular septum
– Separates the two ventricles
• Interatrial septum
– Separates the two atria
The Heart: Valves
• Allow blood to flow in only one direction to
prevent backflow
• Four valves
– Atrioventricular (AV) valves—between atria and
ventricles
• Bicuspid (mitral) valve (left side of heart)
• Tricuspid valve (right side of heart)
– Semilunar valves—between ventricle and artery
• Pulmonary semilunar valve
• Aortic semilunar valve
• AV valves
– Anchored in place by chordae tendineae (“heart
strings”)
– Open during heart relaxation and closed during
ventricular contraction
• Semilunar valves
– Closed during heart relaxation but open during
ventricular contraction
• Notice these valves operate opposite of one
another to force a one-way path of blood
through the heart
Heart Sounds
• Heart sounds are made by the valves as they
open and close
• Valves control flow of blood from one
chamber to another
• Prevent backflow
The Heart: Associated Great Vessels
• Arteries
– Aorta
• Leaves left ventricle
– Pulmonary arteries
• Leave right ventricle
• Veins
– Superior and inferior venae cavae
• Enter right atrium
– Pulmonary veins (four)
• Enter left atrium
Blood Flow Through the Heart
• Superior and inferior venae cavae dump blood
into the right atrium
• From the right atrium, through the tricuspid
valve, blood travels to the right ventricle
• From the right ventricle, blood leaves the
heart as it passes through the pulmonary
semilunar valve into the pulmonary trunk
• Pulmonary trunk splits into right and left
pulmonary arteries that carry blood to the
lungs
• Oxygen is picked up and carbon dioxide is
dropped off by blood in the lungs
• Oxygen-rich blood returns to the heart
through the four pulmonary veins
• Blood enters the left atrium and travels
through the bicuspid valve into the left
ventricle
• From the left ventricle, blood leaves the heart
via the aortic semilunar valve and aorta
How does the Heart work?
STEP ONE
blood from
the body
blood
from the
lungs
The heart beat begins when
the heart muscles relax and
blood flows into the atria.
How does the Heart work?
STEP TWO
The atria then contract
and the valves open to
allow blood into the
ventricles.
How does the Heart work?
STEP THREE
The valves close to stop
blood flowing backwards.
The ventricles contract
forcing the blood to leave
the heart.
At the same time, the atria
are relaxing and once
again filling with blood.
The cycle then repeats
itself.
Heart Beats (Lub Dub)
• Sinoatrial (SA) Node
– Group of cells on the wall of the right atrium near the
entrance of the superior vena cava
– “Pacemaker” of the heart
• Atrioventricular (AV) Node
– Electrically connects the atria and ventricles
– Signals go from the SA Node through the Purkinje
fibers allowing the ventricles to contract