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11
PART A
The Cardiovascular
System
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Cardiovascular System
 A closed system of the heart and blood
vessels
 The heart pumps blood
 Blood vessels allow blood to circulate to
all parts of the body
 The function of the cardiovascular system is
to deliver oxygen and nutrients and to remove
carbon dioxide and other waste products
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The Heart
 Location
 Thorax between the lungs
 Pointed apex directed toward left hip &
rests on diaphragm
 Base from which great vessels emerge
points toward right shoulder & lies
beneath 2nd rib
 About the size of your fist
 Less than 1 pound
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The Heart
Figure 11.1
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The Heart: Coverings
 Pericardium – a double serous membrane
 Visceral pericardium (epicardium)
 Next to heart; part of heart wall
 Parietal pericardium
 Outside layer
 Reinforced by dense connective tissue (fibrous
pericardium)
 Protects heart
 Anchors it to the diaphragm & sternum
 Serous fluid fills the space between the layers of
pericardium
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The Heart: Heart Wall
 Three layers
 Epicardium (visceral pericardium)
 Outside layer
 Continuous with the parietal pericardium
 Connective tissue layer
 Myocardium
 Middle layer
 Mostly cardiac muscle
 Reinforced internally by dense fibrous connective tissue
(“Skeleton of the heart”)
 Endocardium
 Inner layer
 Endothelium lines chambers; continuous w/ vessels entering &
leaving heart – helps blood flow smoothly through heart
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External Heart Anatomy
Figure 11.2a
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The Heart: Chambers
 Right and left side act as separate pumps
 Four chambers
 2 Atria = Receiving chambers
 Right atrium
 Left atrium
 2 Ventricles = Discharging chambers (Pumps)
 Right ventricle
 Forms most of heart’s anterior surface; pulmonary circuit
pump
 Left ventricle
 Forms apex; systemic circuit pump
 Walls are substantially thicker; more powerful to pump
blood throughout body
Figure 11.2c
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The Heart: Chambers
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Pulmonary Circulation
 Right side = pulmonary circuit pump
 Right atria receives deoxygenated blood from the body
via the superior and inferior vena cava
 Blood flows through the right atrioventricular (AV) valve
(tricuspid valve) into the right ventricle
 Right ventricle pumps deoxygenated blood out through
the pulmonary semilunar valves into the pulmonary trunk
that splits into right & left pulmonary arteries, which
carry blood to the lungs
 Oxygen is picked up & carbon dioxide is unloaded
 Oxygen-rich blood is returned to the left atria via 4
pulmonary veins
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Systemic Circulation
 Left side = systemic circuit pump
 Blood flows from the left atria through the left
atrioventricular (AV) valve (bicuspid,or mitral
valve) into the left ventricle
 Left ventricle pumps oxygenated blood out
through the aortic semilunar valves into the aorta
from which the systemic arteries branch to
supply body tissues
 From left ventricle to the aorta to arteries to
arterioles to capillaries to venules to veins to the
vena cava to the right atrium
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Blood Circulation
Figure 11.3
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The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
 Atrioventricular valves between atria and ventricles prevent
backflow into atria when ventricles contract – hang limply when
heart is relaxed
 Bicuspid or mitral valve (left)
 2 flaps, or cusps, of endocardium
 Tricuspid valve (right)
 3 flaps
 Semilunar valves between ventricle and artery with 3 leaflets that fit
tightly together when closed
 Pulmonary semilunar valve
 Aortic semilunar valve
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The Heart: Valves
 Valves open as blood is pumped through
 Held in place by chordae tendineae (“heart
strings”)
 Close to prevent backflow
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Operation of Heart Valves
Figure 11.4
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The Heart: Associated Great Vessels
 Aorta
 Leaves left ventricle
 Pulmonary arteries
 Leave right ventricle
 Vena cava
 Enters right atrium
 Pulmonary veins (four)
 Enter left atrium
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Coronary Circulation
 Blood in the heart chambers does not nourish
the myocardium
 The heart has its own nourishing circulatory
system
 Coronary arteries branch from base of
aorta encircling heart in coronary sulcus
(AV groove)
 Cardiac veins empty into the coronary
sinus on the back side of the heart which
empties into the right atrium
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The Heart: Conduction System
 Intrinsic conduction system
(nodal system)
 Heart muscle cells contract, without nerve
impulses, in a regular, continuous way
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The Heart: Conduction System
 Special tissue sets the pace
 Sinoatrial node
 In right atrium
 Pacemaker
 Atrioventricular node
 At junction of the atria & ventricles
 Atrioventricular bundle
 a.k.a. bundle of His
 Bundle branches
 Right & left located in the interventricular septum
 Purkinje fibers
 Spread within muscles of ventricle walls
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Heart Contractions
 Contraction is initiated by the sinoatrial node
 Sequential stimulation occurs at other
autorhythmic cells
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Heart Contractions
Figure 11.5
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Filling of Heart Chambers – the Cardiac
Cycle = one complete heartbeat
Figure 11.6
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The Heart: Cardiac Cycle
 Average heart beats 75 times/minute, so
cardiac cycle = 0.8 seconds
 Atria contract simultaneously
 Atria relax, then ventricles contract starting at
the apex and moving toward the atria
 Systole = contraction
 Diastole = relaxation
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The Heart: Cardiac Cycle
 Cardiac cycle – events of one complete heart
beat
 Mid-to-late diastole – blood flows into
ventricles
 Ventricular systole – blood pressure builds
before ventricle contracts, pushing out
blood; atria are relaxed & filling again
 Early diastole – atria finish re-filling,
ventricular pressure is low
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Heart Sounds
 When using a stethoscope, 2 distinct sounds
 “Lub”
 Caused by the closing of the AV valves
 Longer and louder
 “Dup” or “dub”
 Occurs when the semilunar valves close at
the end of systole
 Short and sharp
 Lub-dup, pause, lub-dup, pause, and so on
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The Heart: Cardiac Output
 Cardiac output (CO)
 Amount of blood pumped out by each side of the
heart in one minute (ventricles)
 CO = (heart rate [HR]) x (stroke volume [SV])
 Stroke volume
 Volume of blood pumped by each ventricle in
one contraction
 Average adult CO = 75 beats/min. X 70 ml/min. =
5250ml/min.
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Cardiac Output Regulation
Figure 11.7
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The Heart: Regulation of Heart Rate
 Stroke volume usually remains relatively
constant
 Starling’s law of the heart – the more that
the cardiac muscle is stretched, the
stronger the contraction
 Changing heart rate is the most common way
to change cardiac output
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The Heart: Regulation of Heart Rate
 Increased heart rate
 Sympathetic nervous system
 Crisis
 Low blood pressure
 Hormones
 Epinephrine
 Thyroxine
 Exercise
 Decreased blood volume
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The Heart: Regulation of Heart Rate
 Decreased heart rate
 Parasympathetic nervous system
 High blood pressure or blood volume
 Decreased venous return
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Blood Vessels: The Vascular System
 Taking blood to the tissues and back
 Arteries
 Arterioles
 Capillaries
 Venules
 Veins
Figure 11.8a
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The Vascular System
 Vessels have 3 layers or tunics
Figure 11.8b
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Differences Between Blood Vessel Types
 Walls of arteries are the thickest
 Lumens of veins are larger
 Larger veins have valves that prevent
backflow of blood
 Skeletal muscle “milks” blood in veins
toward the heart
 Walls of capillaries are only one cell layer
thick to allow for exchanges between blood
and tissue
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Movement of Blood Through Vessels
 Most arterial blood is
pumped by the heart
 Veins use the milking
action of muscles to
help move blood
Figure 11.9
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Capillary Exchange
 Substances exchanged due to concentration
gradients
 Oxygen and nutrients leave the blood
 Carbon dioxide and other wastes leave the
cells
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Capillary Exchange: Mechanisms
 Direct diffusion across plasma membranes
 Endocytosis or exocytosis
 Some capillaries have gaps (intercellular
clefts)
 Plasma membrane not joined by tight
junctions
 Fenestrations of some capillaries
 Fenestrations = pores
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Diffusion at Capillary Beds
Figure 11.20
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Special Circulations:
Hepatic Portal Circulation
 Veins of the hepatic portal circulation drain
the digestive organs, spleen and pancreas and
deliver this blood to the liver via hepatic
portal vein
 Liver processes glucose, fat and protein
before they enter the systemic circulation
 Some nutrients are removed to be stored for
later release to the blood
 Veins feed the liver circulation
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Hepatic Portal Circulation
Figure 11.14
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Special Circulations:
Circulation to the Fetus
 Lungs and digestive system are not functional
 All nutrient, excretory and gas exchanges occur
through the placenta
 Umbilical cord contains 3 blood vessels
 1 large umbilical vein
 Carries nutrients and oxygen to the fetus
 2 smaller umbilical arteries
 Carries carbon dioxide and waste from fetus
to placenta
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Circulation to the Fetus
 As blood flows to the fetal heart, most of it bypasses the
immature liver via the ductus venosus and enters the inferior
vena cava and is carried to the right atrium
 Since lungs are nonfunctional, 2 shunts bypass them
 Blood entering right atrium is shunted into the left atrium
via foramen ovale, an opening in the interatrial septum
 Blood that enters the right ventricle is pumped out the
pulmonary trunk and shunted into the ductus arteriosus,
which connects it to the aorta
 Aorta carries blood to fetal tissues and ultimately back to the
placenta via the umbilical arteries
 Shortly after birth, the foramen ovale closes and the ductus
arteriosus collapses and is converted to the ligamentum
arteriosum
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Circulation to the Fetus
Figure 11.15
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Developmental Aspects of the
Cardiovascular System
 A simple “tube heart” develops in the embryo
and pumps by the fourth week
 The heart becomes a four-chambered organ
by the end of seven weeks
 Few structural changes occur after the
seventh week
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Pulse
 Pulse – pressure
wave of blood
 Monitored at
“pressure points”
where pulse is
easily palpated
 Resting pulse
averages 70-76
beats/min
Figure 11.16
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Blood Pressure
 Measurements by health professionals are
made on the pressure in large arteries
 Systolic – pressure at the peak of
ventricular contraction
 Diastolic – pressure when ventricles relax
 Pressure in blood vessels decreases as the
distance away from the heart increases
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Measuring Arterial Blood Pressure
Figure 11.18
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Comparison of Blood Pressures in
Different Vessels
Figure 11.17
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Blood Pressure: Effects of Factors
 Neural factors
 Autonomic nervous system adjustments
(sympathetic division) cause vasoconstriction,
which increases BP
 Renal factors
 Regulation by altering blood volume
 Allowing more water to leave as urine, lowers BP
 Retaining water raises BP
 Renin – hormonal control – raises BP
(vasoconstriction)
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Blood Pressure: Effects of Factors
 Temperature
 Heat has a vasodilation effect
 Cold has a vasoconstricting effect
 Chemicals
 Various substances can cause increases or
decreases
 Increase BP – epinephrine and nicotine
 Decrease BP – alcohol and histamine
 Diet
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Factors Determining Blood Pressure
Figure 11.19
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Variations in Blood Pressure
 Human normal range is variable
 Normal
 140–110 mm Hg systolic
 80–75 mm Hg diastolic
 Hypotension (low BP)
 Low systolic (below 100 mm HG)
 Often associated with long life and an old age free
of illness
 Chronic hypotension may hint at poor nutrition
 Hypertension
 High systolic (above 140 mm HG)
 Can be dangerous if it is chronic
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