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PowerLecture:PowerLecture:Chapter 9Chapter 9
Circulation - The Heart Circulation - The Heart and Blood Vesselsand Blood Vessels
Learning ObjectivesLearning Objectives
List the basic components of the human List the basic components of the human circulatory system.circulatory system.
Trace the routes of blood flow in the human Trace the routes of blood flow in the human cardiovascular system.cardiovascular system.
Explain the factors that cause blood to exist Explain the factors that cause blood to exist under different pressures.under different pressures.
Describe the major cardiovascular disorders Describe the major cardiovascular disorders and their causes. and their causes.
The Breath of LifeThe Breath of Life
During sudden cardiac arrest the During sudden cardiac arrest the heart stops its regular beating.heart stops its regular beating.
CPR (cardiopulmonary resuscitation) CPR (cardiopulmonary resuscitation) is an immediate life-saving technique.is an immediate life-saving technique.
As soon as possible a defibrillator As soon as possible a defibrillator should be used to shock the heart should be used to shock the heart back to its usual rhythm; AEDs back to its usual rhythm; AEDs (automated external defibrillators) are (automated external defibrillators) are now available in many public places.now available in many public places.
The heart, and its associated blood The heart, and its associated blood vessels, is a complicated life-vessels, is a complicated life-sustaining system.sustaining system.
How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main system, access “JoinIn Clicker Content” from the PowerLecture main menu. menu.
Would you favor mandatory CPR training in Would you favor mandatory CPR training in high schools?high schools? a. Yes, it would save countless lives.a. Yes, it would save countless lives. b. No, it’s just another graduation requirement.b. No, it’s just another graduation requirement.
Section 1Section 1
The Cardiovascular The Cardiovascular System – Moving Blood System – Moving Blood
Through the BodyThrough the Body
The Cardiovascular System – Moving The Cardiovascular System – Moving Blood Through the BodyBlood Through the Body
The heart and blood vessels make up the The heart and blood vessels make up the cardiovascular system. cardiovascular system.
The The cardiovascular systemcardiovascular system has two major has two major elements:elements:
• The The heartheart is the muscular pump that generates the is the muscular pump that generates the pressure required to move the blood through the pressure required to move the blood through the body.body.
• Blood vesselsBlood vessels are the distribution tubes of varying are the distribution tubes of varying diameters.diameters.
The route of circulation: heart >>> arteries >>> The route of circulation: heart >>> arteries >>> arterioles >>> capillaries >>> venules >>> veins arterioles >>> capillaries >>> venules >>> veins and finally back to the heart.and finally back to the heart.
jugular veins
superior vena cava
pulmonary veins
hepatic portal vein
renal vein
inferior vena cava
iliac veins
femoral vein
carotid arteries
ascending aorta
pulmonary arteries
coronary arteries
renal artery
brachial artery
abdominal aorta
iliac arteries
femoral artery
Fig. 9.1, p.158
heart
The Cardiovascular System – Moving The Cardiovascular System – Moving Blood Through the BodyBlood Through the Body
Circulating blood is vital to maintain Circulating blood is vital to maintain homeostasis.homeostasis.
The cardiovascular system is the body’s internal The cardiovascular system is the body’s internal rapid-transport system for oxygen, nutrients, rapid-transport system for oxygen, nutrients, secretions, and wastes via the blood.secretions, and wastes via the blood.
Homeostasis depends on the reliable supply of Homeostasis depends on the reliable supply of blood to all of the body.blood to all of the body.
food, water intake oxygen intake
DIGESTIVE SYSTEM
RESPIRATORY SYSTEM
CIRCULATORY SYSTEM
URINARY SYSTEM
elimination of food residues
elimination of excess water, salts, wastes
elimination of carbon dioxide
nutrients, water, salts
water, solutes
rapid transport to and from all living cells
oxygen carbon dioxide
Fig. 9.2, p.159
The Cardiovascular System – Moving The Cardiovascular System – Moving Blood Through the BodyBlood Through the Body
The cardiovascular system is linked to the The cardiovascular system is linked to the lymphatic system.lymphatic system.
Because of the pressure in the cardiovascular Because of the pressure in the cardiovascular system, water and proteins leak out to become system, water and proteins leak out to become part of the interstitial fluid.part of the interstitial fluid.
The The lymphatic systemlymphatic system vessels pick up the fluid vessels pick up the fluid and return it to the general circulation.and return it to the general circulation.
The Heart: A Double Pump The Heart: A Double Pump
The heart is a durable pump made mostly The heart is a durable pump made mostly of cardiac muscle (of cardiac muscle (myocardiummyocardium).).
The heart is surrounded by a tough, fibrous sac The heart is surrounded by a tough, fibrous sac
((pericardiumpericardium).). The inner lining of the heart is the The inner lining of the heart is the
endocardiumendocardium; it is composed of connective ; it is composed of connective tissue and epithelial cells (tissue and epithelial cells (endotheliumendothelium).).
The Heart: A Double Pump The Heart: A Double Pump
The heart has two halves and four The heart has two halves and four chambers.chambers.
The The septumseptum divides the heart into two halves, divides the heart into two halves, right and left.right and left.
• Each half consists of an Each half consists of an atriumatrium (receiving chamber) (receiving chamber) and a and a ventricleventricle (pumping chamber) separated by an (pumping chamber) separated by an atrioventricular valveatrioventricular valve (AV valve). (AV valve).
• The AV valve on the right is a The AV valve on the right is a tricuspid valvetricuspid valve; the ; the one on the left is the one on the left is the bicuspidbicuspid, or , or mitral valvemitral valve..
• Chordae tendineaeChordae tendineae (“heartstrings”) connect the AV (“heartstrings”) connect the AV valve flaps to the ventricle wall.valve flaps to the ventricle wall.
Blood exits each ventricle through a Blood exits each ventricle through a semilunar semilunar valvevalve..
three cusps
two cusps
left atrioventricular valve (bicuspid or mitral valve)
left semilunar valve (between left ventricle and aorta)
right atrioventricular valve (tricuspid)
right semilunar valve (between right ventricle and pulmonary arteries)
front of chest
Fig. 9.3c, p.160
The Heart: A Double Pump The Heart: A Double Pump
Heart muscle cells are serviced by the coronary Heart muscle cells are serviced by the coronary circulation; circulation; coronary arteriescoronary arteries branch off the branch off the aortaaorta, forming a capillary bed around the heart., forming a capillary bed around the heart.
Figure 9.4bFigure 9.4b
coronaryartery
© 2007 Thomson Higher Education
aorta
(left pulmonary artery)
(left pulmonary veins)
cardiac vein
left coronary artery
(superior vena cava)
right coronary artery
cardiac vein
(inferior vena cava)
Fig. 9.4a, p.161
© 2007 Thomson Higher Education
superior vena cava
right semilunar valve
right pulmonary veins
right atrium
right AV valve (opened)
right ventricle
inferior vena cava
septum (partition that divides the heart into two halves)
aorta
trunk of pulmonaryarteries
left semilunar valve
left pulmonaryveins
left atrium
left AV valve (opened) left ventricle
endothelium,connective tissue
pericardium
Fig. 9.3b, p.160
muscles that keep valve from pointing wrong way
myocardium
The Heart: A Double Pump The Heart: A Double Pump
In a “heartbeat,” the heart’s chambers In a “heartbeat,” the heart’s chambers contract, then relax.contract, then relax.
The The cardiac cyclecardiac cycle is a sequence of contraction is a sequence of contraction ((systolesystole) and relaxation () and relaxation (diastolediastole).).
• As the atria fill, the ventricles are relaxed.As the atria fill, the ventricles are relaxed.• Pressure of the blood in the atria forces the AV Pressure of the blood in the atria forces the AV
valves open; the ventricles fill as the atria contract.valves open; the ventricles fill as the atria contract.• When the ventricles contract, the AV valves close, When the ventricles contract, the AV valves close,
and blood flows out through the semilunar valves.and blood flows out through the semilunar valves.
The Heart: A Double Pump The Heart: A Double Pump
The The cardiac outputcardiac output is the amount of blood is the amount of blood each ventricle can pump in a minute; on each ventricle can pump in a minute; on average the output from each ventricle is about average the output from each ventricle is about 5 liters.5 liters.
The heart sound “lub” is made by the closing of The heart sound “lub” is made by the closing of the AV valves; the “dup” sound is the closure of the AV valves; the “dup” sound is the closure of the semilunar valves.the semilunar valves.
Atria, contract,and fluid pressure in ventricles rises sharply.
Ventriclesrelax even as the atriabegin tofill and startanother cycle.
Ventricles contract;blood is pumpedinto the pulmonaryartery and the aorta
Fluid pressure in filling atriaopens AV valves; blood flows intoventricles
Heart sounds
Fig. 9.5, p.161
14
3
2
Fig. 9.5, p.161
Heart sounds
Atria, contract,and fluid pressure in ventricles rises sharply.
1Fluid pressure in filling atriaopens AV valves; blood flows intoventricles
4
Ventriclesrelax even as the atriabegin tofill and startanother cycle.
3
Ventricles contract;blood is pumpedinto the pulmonaryartery and the aorta
2
Stepped Art
The Two Circuits of Blood FlowThe Two Circuits of Blood Flow
The pulmonary circuit: Blood picks up The pulmonary circuit: Blood picks up oxygen in the lungs.oxygen in the lungs.
The The pulmonary circuitpulmonary circuit receives blood from the receives blood from the tissues, taking it through the lungs for gas tissues, taking it through the lungs for gas exchange.exchange.
The path of blood flow: blood from tissues The path of blood flow: blood from tissues enters the right atrium >>> tricuspid valve >>> enters the right atrium >>> tricuspid valve >>> right ventricle >>>right semilunar valve >>> right ventricle >>>right semilunar valve >>> pulmonary arteries >>> lungs >>> pulmonary pulmonary arteries >>> lungs >>> pulmonary veins >>> left atrium.veins >>> left atrium.
The Two Circuits of Blood FlowThe Two Circuits of Blood Flow
Blood returning from the body tissues is high in Blood returning from the body tissues is high in carbon dioxide and low in oxygen; these carbon dioxide and low in oxygen; these concentrations are reversed after passage concentrations are reversed after passage through the lung capillaries.through the lung capillaries.
right pulmonary artery left pulmonary artery
capillary bed of right lung
pulmonarytrunk
capillary bedof left lung
(to systemic circuit)
pulmonary veins
(from systemic circuit)
heart
Fig. 9.6a, p.162
© 2007 Thomson Higher Education
The Two Circuits of Blood FlowThe Two Circuits of Blood Flow
In the systemic circuit, blood travels to and In the systemic circuit, blood travels to and from tissues.from tissues.
In the In the systemic circuitsystemic circuit, oxygenated blood is , oxygenated blood is pumped through the body.pumped through the body.
Blood moves from the left atrium >>> bicuspid Blood moves from the left atrium >>> bicuspid valve >>> left ventricle >>>left semilunar valve valve >>> left ventricle >>>left semilunar valve >>> aorta >>> body tissues.>>> aorta >>> body tissues.
Blood from the upper body travels through the Blood from the upper body travels through the superior vena cavasuperior vena cava; blood from the lower body ; blood from the lower body travels through the travels through the inferior vena cavainferior vena cava..
The Two Circuits of Blood FlowThe Two Circuits of Blood Flow
Blood from the digestive tract is shunted Blood from the digestive tract is shunted through the liver for processing.through the liver for processing.
After a meal, blood laden with nutrients is After a meal, blood laden with nutrients is carried from the digestive tract in the carried from the digestive tract in the hepatic hepatic portal veinportal vein to the liver capillaries. to the liver capillaries.
There it passes through the liver capillary beds There it passes through the liver capillary beds before leaving via the before leaving via the hepatic veinhepatic vein to return to to return to the general circulation; oxygenated blood the general circulation; oxygenated blood reaches the liver through the reaches the liver through the hepatic arteryhepatic artery..
© 2007 Thomson Higher Education
capillary beds of headand upper extremities
(to pulmonarycircuit) aorta
(frompulmonarycircuit)
heart
capillary beds of other organs in thoracic cavity
diaphragm (muscular partition between thoracic and abdominal cavities)
capillary bed of liver
capillary beds of other abdominal organs and lower extremities
capillary bed of intestines
Fig. 9.6b, p.162
Systemic circuit for blood flow
© 2007 Thomson Higher Education
lungs
heart’s right half heart’s left half
liver
digestive tract
kidneys
skeletal muscle
brain
skin
bone
cardiac muscle
all other regions
100%
6%
20%
15%
13%
9%
5%
3%
8%
Fig. 9.6c, p.162
21%
Electrical signals from “pacemaker” cells Electrical signals from “pacemaker” cells drive the heart’s contractions.drive the heart’s contractions.
Cardiac muscle cells are linked by Cardiac muscle cells are linked by intercalated intercalated discsdiscs,, which rapidly pass signals to contract which rapidly pass signals to contract throughout the heart.throughout the heart.
• The The cardiac conduction systemcardiac conduction system consists of consists of noncontractile cells that are self-excitatory noncontractile cells that are self-excitatory ((pacemakerpacemaker cells). cells).
• Excitation for a heartbeat is initiated in the Excitation for a heartbeat is initiated in the sinoatrialsinoatrial ((SASA) ) nodenode; it then passes to the ; it then passes to the atrioventricularatrioventricular ((AVAV) ) nodenode and on to the and on to the Purkinje fibersPurkinje fibers, which , which make contact with the muscle cells that result in make contact with the muscle cells that result in ventricular contraction.ventricular contraction.
How Cardiac Muscles ContractHow Cardiac Muscles Contract
SA node
AV node
bundle of connecting muscle fibers
Purkinje fibers
Fig. 9.8a, p.164
contractile heartmuscle cells
It is the action of the It is the action of the cardiac pacemakercardiac pacemaker (SA (SA node) that produces our normal heartbeat.node) that produces our normal heartbeat.
The nervous system adjusts heart activity.The nervous system adjusts heart activity. The nervous system can adjust the rate and The nervous system can adjust the rate and
strength of cardiac muscle contraction; strength of cardiac muscle contraction; stimulation by one set of nerves increases the stimulation by one set of nerves increases the rate and strength while stimulation by other rate and strength while stimulation by other nerves decreases heart rate.nerves decreases heart rate.
Centers for nervous control of the heart lie in Centers for nervous control of the heart lie in the spinal cord and the brain.the spinal cord and the brain.
How Cardiac Muscles ContractHow Cardiac Muscles Contract
Blood PressureBlood Pressure
Blood exerts pressure against the walls of Blood exerts pressure against the walls of blood vessels.blood vessels.
The force of blood against The force of blood against
the vessel walls can be the vessel walls can be
measured as measured as blood pressureblood pressure.. Normal Normal systolic pressuresystolic pressure
(peak pressure in the aorta) (peak pressure in the aorta)
is 120 mm of Hg; normal is 120 mm of Hg; normal diastolic pressurediastolic pressure (lowest pressure in the aorta) is 80 mm.(lowest pressure in the aorta) is 80 mm.
Figure 9.9Figure 9.9
Blood PressureBlood Pressure
Blood pressure values give important clues Blood pressure values give important clues as to the condition of the vessels and the flow as to the condition of the vessels and the flow of blood through them.of blood through them. In In hypertensionhypertension, the blood pressure is too high, , the blood pressure is too high,
which can lead to stroke or heart attack.which can lead to stroke or heart attack. In In hypotensionhypotension, the blood pressure is too low; , the blood pressure is too low;
loss of water or blood volume can lead to loss of water or blood volume can lead to circulatory shockcirculatory shock..
Arteries are large blood pipelines.Arteries are large blood pipelines. Because of their elastic walls, Because of their elastic walls,
arteriesarteries tend to “smooth out” the tend to “smooth out” the
pressure changes associated with pressure changes associated with
the discontinuous pumping cycle of the discontinuous pumping cycle of
the heart (felt as a the heart (felt as a pulsepulse).). Because of their large Because of their large diameters, arteries diameters, arteries
present little resistance to flow; blood pressure present little resistance to flow; blood pressure does not decrease very much in them.does not decrease very much in them.
Structure and Functions of Blood VesselsStructure and Functions of Blood Vessels
connective tissue coat
smoothmuscle
endothelium
Artery
elastic tissue
elastic tissue
Fig. 9.11a, p.166
Arterioles are control points for blood flow.Arterioles are control points for blood flow. Arteries branch into smaller Arteries branch into smaller arteriolesarterioles, where , where
the greatest pressure drop occurs.the greatest pressure drop occurs. The wall of an arteriole has rings of smooth The wall of an arteriole has rings of smooth
muscle over a single layer of elastic fibers.muscle over a single layer of elastic fibers. Arterioles serve as control points where Arterioles serve as control points where
adjustments can be made in blood volume adjustments can be made in blood volume
distribution.distribution.
Structure and Functions of Blood VesselsStructure and Functions of Blood Vessels
Capillaries are specialized for diffusion.Capillaries are specialized for diffusion. A A capillarycapillary is the smallest and thinnest tube in is the smallest and thinnest tube in
the path of circu lation and is specialized for the path of circu lation and is specialized for exchange of substances with interstitial fluid.exchange of substances with interstitial fluid.
Total resistance is less than in arterioles so the Total resistance is less than in arterioles so the drop in blood pressure is not as great.drop in blood pressure is not as great.
Venules and veins return blood to the heart.Venules and veins return blood to the heart. Capillaries merge into Capillaries merge into venulesvenules.. Venules merge into Venules merge into veinsveins..
Structure and Functions of Blood VesselsStructure and Functions of Blood Vessels
• Veins are blood volume reservoirs (50-60% of blood Veins are blood volume reservoirs (50-60% of blood volume) because their walls can distend or contract.volume) because their walls can distend or contract.
• Skeletal muscles adjacent to veins squeeze the walls Skeletal muscles adjacent to veins squeeze the walls
to move the blood along on its way back to the heart; to move the blood along on its way back to the heart;
valves prevent backflow.valves prevent backflow. Varicose veinsVaricose veins can form when the veins have can form when the veins have
become overstretched, and the valves become overstretched, and the valves weakened.weakened.
Structure and Functions of Blood VesselsStructure and Functions of Blood Vessels
Vessels help control blood pressure.Vessels help control blood pressure. The brain monitors signals from various arteries The brain monitors signals from various arteries
to determine the rate of heartbeat and any to determine the rate of heartbeat and any changes needed in vessel diameters.changes needed in vessel diameters.
• If the blood pressure increases, the arterioles are If the blood pressure increases, the arterioles are instructed to relax (instructed to relax (vasodilationvasodilation).).
• If the pressure decreases, the diameter of the If the pressure decreases, the diameter of the arterioles decreases (arterioles decreases (vasoconstrictionvasoconstriction).).
In the In the baroreceptor reflexbaroreceptor reflex, special receptors in , special receptors in the the carotid arteriescarotid arteries monitor changes in blood monitor changes in blood pressure and send the information to the brain pressure and send the information to the brain for action.for action.
Structure and Functions of Blood VesselsStructure and Functions of Blood Vessels
Fig. 9.12, p.166
Blo
od
pre
ssu
re (
mm
Hg
)
120
80
40
0
arteries
(diastolic)
arterioles
capillaries veins
Fig. 9.12, p.166
(systolic)
venules
Section 7Section 7
Capillaries: Where Blood Capillaries: Where Blood Exchanges Substances Exchanges Substances
with Tissueswith Tissues
Capillaries: Where Blood Exchanges Capillaries: Where Blood Exchanges Substances with TissuesSubstances with Tissues
A vast network of capillaries weaves close A vast network of capillaries weaves close to nearly all living body cells.to nearly all living body cells.
Capillaries comprise most Capillaries comprise most
of the cardiovascular of the cardiovascular
system.system. The velocity of blood flow The velocity of blood flow
slows as the diameter of the vessels slows as the diameter of the vessels decreases.decreases.
It is slowest in the capillaries to provide for It is slowest in the capillaries to provide for
maximum exchange.maximum exchange.Figure 9.14aFigure 9.14a
Capillaries: Where Blood Exchanges Capillaries: Where Blood Exchanges Substances with TissuesSubstances with Tissues
Many substances enter and leave Many substances enter and leave capillaries by diffusion.capillaries by diffusion.
Diffusion is a slow process and is not efficient Diffusion is a slow process and is not efficient over long distances.over long distances.
Billions of capillaries ensure that all cells are Billions of capillaries ensure that all cells are
near enough to a capillary to receive nutrients near enough to a capillary to receive nutrients and give up wastes; and give up wastes;
blood flow blood flow is slow is slow
enough here to allow enough here to allow
diffusion.diffusion.Figure 9.14bFigure 9.14b
Capillaries: Where Blood Exchanges Capillaries: Where Blood Exchanges Substances with TissuesSubstances with Tissues
Some substances pass through “pores” in Some substances pass through “pores” in capillary walls.capillary walls.
Water-filled, slitlike areas between the cells of Water-filled, slitlike areas between the cells of capillary walls allow water-soluble substances capillary walls allow water-soluble substances to exit the blood due to pressure (to exit the blood due to pressure (bulk flowbulk flow).).
This movement of fluids and solutes is This movement of fluids and solutes is important to homeostasis and maintaining blood important to homeostasis and maintaining blood pressure.pressure.
inward-directedosmotic movement
cells of tissue
outward-directedbulk flow
blood from arteriole
blood to venule
Fig. 9.15, p.169
Capillaries: Where Blood Exchanges Capillaries: Where Blood Exchanges Substances with TissuesSubstances with Tissues
Blood in capillaries flows onward to Blood in capillaries flows onward to venules.venules.
Precapillary sphinctersPrecapillary sphincters regulate the flow of regulate the flow of blood into capillaries.blood into capillaries.
Capillaries are the “turnaround points” for the Capillaries are the “turnaround points” for the cardiovascular system.cardiovascular system.
Cardiovascular DisordersCardiovascular Disorders
Many factors may influence your chance of Many factors may influence your chance of developing a cardiovascular disorder.developing a cardiovascular disorder.
Some risk factors include: family history, Some risk factors include: family history, hypertension, obesity, smoking, or simply age.hypertension, obesity, smoking, or simply age.
Inflammation, which leads to the production of Inflammation, which leads to the production of C-reactive proteinC-reactive protein by the liver, may also play a by the liver, may also play a role in cardiovascular disease.role in cardiovascular disease.
Cardiovascular DisordersCardiovascular Disorders
Arteries can be clogged or weakened.Arteries can be clogged or weakened. ArteriosclerosisArteriosclerosis is a hardening of the arteries. is a hardening of the arteries.
When cholesterol and other lipids build up in When cholesterol and other lipids build up in these hardened arteries, these hardened arteries, atherosclerosisatherosclerosis occurs.occurs.
• Atherosclerotic plaquesAtherosclerotic plaques can impede blood flow. can impede blood flow.• Coronary arteries are narrow and vulnerable to Coronary arteries are narrow and vulnerable to
clogging with these plaques; chest pain (clogging with these plaques; chest pain (angina angina pectorispectoris) or heart attack may occur.) or heart attack may occur.
Cardiovascular DisordersCardiovascular Disorders
High blood levels of cholesterol can lead to High blood levels of cholesterol can lead to atherosclerosis.atherosclerosis.
Low-density lipoproteinsLow-density lipoproteins (LDL or “bad” (LDL or “bad” cholesterol) carry cholesterol into the arterial cholesterol) carry cholesterol into the arterial walls; walls; high-density lipoproteinshigh-density lipoproteins (HDL or (HDL or “good” cholesterol) remove it.“good” cholesterol) remove it.
A total of 200 mg cholesterol per milliliter of A total of 200 mg cholesterol per milliliter of blood or less is considered acceptable for most blood or less is considered acceptable for most people.people.
Cardiovascular DisordersCardiovascular Disorders
Surgery may be needed to clear blocked Surgery may be needed to clear blocked arteries.arteries.
Coronary bypassCoronary bypass involves using a large vessel involves using a large vessel from elsewhere in the body to bypass a from elsewhere in the body to bypass a completely blocked artery in the heart.completely blocked artery in the heart.
Fig. 9.17c, p.170
aorta
coronaryarteryblockage
a shunt made of a section taken from one
of the patient’s other blood vessels
Cardiovascular DisordersCardiovascular Disorders
Laser angioplastyLaser angioplasty uses a laser to vaporize uses a laser to vaporize plaques while plaques while balloon angioplastyballoon angioplasty uses small uses small balloons to flatten the plaques to open room in balloons to flatten the plaques to open room in the artery; a wire “stent” may be inserted to the artery; a wire “stent” may be inserted to keep the ballooned area open.keep the ballooned area open.
StatinsStatins are drugs designed to reduce the are drugs designed to reduce the amount of cholesterol in the blood.amount of cholesterol in the blood.
Disease, injury, or defects can weaken artery Disease, injury, or defects can weaken artery walls so they bulge outward due to blood walls so they bulge outward due to blood pressure, forming an pressure, forming an aneurysmaneurysm; aneurysms ; aneurysms can be fatal if the artery wall bursts.can be fatal if the artery wall bursts.
Cardiovascular DisordersCardiovascular Disorders
Heart damage can lead to heart attack and Heart damage can lead to heart attack and heart failure.heart failure.
A A heart attackheart attack is damage to or death of heart is damage to or death of heart muscle.muscle.
In In heart failureheart failure, the heart is weak and does not , the heart is weak and does not pump blood as efficiently.pump blood as efficiently.
Cardiovascular DisordersCardiovascular Disorders
Arrhythmias are abnormal heart rhythms.Arrhythmias are abnormal heart rhythms. ElectrocardiogramsElectrocardiograms (ECGs) are recordings of (ECGs) are recordings of
the cardiac cycle and can be used to reveal the cardiac cycle and can be used to reveal irregular heart rhythms.irregular heart rhythms.
ArrhythmiasArrhythmias are irregular heart rhythms; are irregular heart rhythms; bradycardiabradycardia is a below normal rhythm, while is a below normal rhythm, while tachycardiatachycardia is an above normal rhythm. is an above normal rhythm.
Ventricular fibrillationVentricular fibrillation occurs when the occurs when the ventricles contract haphazardly so that blood is ventricles contract haphazardly so that blood is not pumped correctly; this can lead to cardiac not pumped correctly; this can lead to cardiac arrest.arrest.
Cardiovascular DisordersCardiovascular Disorders
A heart-healthy lifestyle.A heart-healthy lifestyle. Lifestyle changes can Lifestyle changes can greatly reduce the risk greatly reduce the risk
of cardiovascular disease.of cardiovascular disease. Diets low in fat and cholesterol, regular Diets low in fat and cholesterol, regular
exercise, and not smoking are three key exercise, and not smoking are three key strategies.strategies.