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Chapter 20Chapter 20 The Cardiovascular System: The Cardiovascular System: The HeartThe Heart

Heart pumps Heart pumps over 1 million over 1 million gallons per yeargallons per year

Over 60,000 Over 60,000 miles of blood miles of blood vesselsvessels

22

Heart LocationHeart Location

Heart is located in the mediastinumHeart is located in the mediastinum area from the sternum to the vertebral column and area from the sternum to the vertebral column and

between the lungsbetween the lungs

Anterior surfaceof heart

33

Heart OrientationHeart Orientation

Apex - directed anteriorly, inferiorly and to the leftApex - directed anteriorly, inferiorly and to the left Base - directed posteriorly, superiorly and to the Base - directed posteriorly, superiorly and to the

rightright Anterior surface - deep to the sternum and ribsAnterior surface - deep to the sternum and ribs Inferior surface - rests on the diaphragm Inferior surface - rests on the diaphragm Right border - faces right lungRight border - faces right lung Left border (pulmonary border) - faces left lungLeft border (pulmonary border) - faces left lung

44

Heart OrientationHeart Orientation

Heart has 2 surfaces: anterior and inferior, Heart has 2 surfaces: anterior and inferior, and 2 borders: right and left and 2 borders: right and left

55

Surface Projection of Surface Projection of the Heartthe Heart

Superior right point at the superior border of the 3Superior right point at the superior border of the 3 rdrd right costal cartilageright costal cartilage

Superior left point at the inferior border of the 2Superior left point at the inferior border of the 2ndnd left left costal cartilage 3cm to the left of midlinecostal cartilage 3cm to the left of midline

Inferior left point at the 5Inferior left point at the 5 thth intercostal space, 9 cm intercostal space, 9 cm from the midlinefrom the midline

Inferior right point at superior border of the 6Inferior right point at superior border of the 6 thth right right costal cartilage, 3 cm from the midlinecostal cartilage, 3 cm from the midline

66

PericardiumPericardium Fibrous pericardiumFibrous pericardium

dense irregular CTdense irregular CT protects and anchors protects and anchors

the heart, prevents the heart, prevents overstretchingoverstretching

Serous pericardiumSerous pericardium thin delicate membranethin delicate membrane contains contains

parietal layer-outer layerparietal layer-outer layer pericardial cavity with pericardial cavity with

pericardial fluidpericardial fluid visceral layer visceral layer

(epicardium) (epicardium)

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Layers of Heart WallLayers of Heart Wall

EpicardiumEpicardium visceral layer of visceral layer of

serous pericardiumserous pericardium

Myocardium Myocardium cardiac muscle cardiac muscle

layer is the bulk of layer is the bulk of the heartthe heart

EndocardiumEndocardium chamber lining & chamber lining &

valvesvalves

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Muscle Bundles of the Muscle Bundles of the MyocardiumMyocardium

Cardiac muscle fibers swirl diagonally around Cardiac muscle fibers swirl diagonally around the heart in interlacing bundlesthe heart in interlacing bundles

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Chambers and Sulci of Chambers and Sulci of the Heartthe Heart Four chambers Four chambers

2 upper atria2 upper atria 2 lower ventricles2 lower ventricles

Sulci - grooves on surface of heart Sulci - grooves on surface of heart containing coronary blood vessels and containing coronary blood vessels and fatfat coronary sulcuscoronary sulcus

encircles heart and marks the boundary encircles heart and marks the boundary between the atria and the ventriclesbetween the atria and the ventricles

anterior interventricular sulcus anterior interventricular sulcus marks the boundary between the ventricles marks the boundary between the ventricles

anteriorlyanteriorly posterior interventricular sulcus posterior interventricular sulcus

marks the boundary between the ventricles marks the boundary between the ventricles posteriorlyposteriorly

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Chambers and SulciChambers and Sulci

Anterior View

1111Posterior View

Chambers and SulciChambers and Sulci

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Right AtriumRight Atrium

Receives blood from 3 sourcesReceives blood from 3 sources superior vena cava, inferior vena cava and coronary sinussuperior vena cava, inferior vena cava and coronary sinus

Interatrial septum partitions the atriaInteratrial septum partitions the atria Fossa ovalis is a remnant of the fetal foramen ovaleFossa ovalis is a remnant of the fetal foramen ovale Tricuspid valveTricuspid valve

Blood flows through into right ventricleBlood flows through into right ventricle has three cusps composed of dense CT covered by has three cusps composed of dense CT covered by

endocardiumendocardium

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Right VentricleRight Ventricle

Forms most of anterior surface of heartForms most of anterior surface of heart Papillary muscles are cone shaped trabeculae carneae (raised Papillary muscles are cone shaped trabeculae carneae (raised

bundles of cardiac muscle)bundles of cardiac muscle) Chordae tendineae: cords between valve cusps and papillary Chordae tendineae: cords between valve cusps and papillary

musclesmuscles Interventricular septum: partitions ventriclesInterventricular septum: partitions ventricles Pulmonary semilunar valve: blood flows into pulmonary trunk Pulmonary semilunar valve: blood flows into pulmonary trunk

1414

Left AtriumLeft Atrium

Forms most of the base of the heartForms most of the base of the heart Receives blood from lungs - 4 pulmonary veins (2 right Receives blood from lungs - 4 pulmonary veins (2 right

+ 2 left)+ 2 left) Bicuspid valve: blood passes through into left ventricleBicuspid valve: blood passes through into left ventricle

has two cuspshas two cusps to remember names of this valve, try the pneumonic LAMBto remember names of this valve, try the pneumonic LAMB

Left Atrioventricular, Mitral, or Bicuspid valveLeft Atrioventricular, Mitral, or Bicuspid valve

1515

Left VentricleLeft Ventricle

Forms the apex of heart Forms the apex of heart Chordae tendineae anchor bicuspid valve to papillary Chordae tendineae anchor bicuspid valve to papillary

muscles muscles (also has trabeculae carneae like right ventricle)(also has trabeculae carneae like right ventricle) Aortic semilunar valve: Aortic semilunar valve:

blood passes through valve into the ascending aortablood passes through valve into the ascending aorta just above valve are the openings to the coronary arteriesjust above valve are the openings to the coronary arteries

1616

Myocardial Thickness and Myocardial Thickness and FunctionFunction

Thickness of myocardium varies according to the Thickness of myocardium varies according to the function of the chamberfunction of the chamber

Atria are thin walled, deliver blood to adjacent ventriclesAtria are thin walled, deliver blood to adjacent ventricles

Ventricle walls are much thicker and strongerVentricle walls are much thicker and stronger right ventricle supplies blood to the lungs (little flow resistance)right ventricle supplies blood to the lungs (little flow resistance) left ventricle wall is the thickest to supply systemic circulationleft ventricle wall is the thickest to supply systemic circulation

1717

Thickness of Cardiac Thickness of Cardiac WallsWalls

Myocardium of left ventricle is much thicker than the right.

1818

Fibrous Skeleton of Fibrous Skeleton of HeartHeart

Dense CT rings surround the valves of the heart, Dense CT rings surround the valves of the heart, fuse and merge with the interventricular septumfuse and merge with the interventricular septum

Support structure for heart valvesSupport structure for heart valves Insertion point for cardiac muscle bundlesInsertion point for cardiac muscle bundles Electrical insulator between atria and ventriclesElectrical insulator between atria and ventricles

prevents direct propagation of AP’s to ventriclesprevents direct propagation of AP’s to ventricles

1919

A-V valves open and allow blood to flow from A-V valves open and allow blood to flow from atria into ventricles when ventricular pressure atria into ventricles when ventricular pressure is lower than atrial pressureis lower than atrial pressure occurs when ventricles are relaxed, chordae occurs when ventricles are relaxed, chordae

tendineae are slack and papillary muscles are tendineae are slack and papillary muscles are relaxedrelaxed

Atrioventricular Valves Atrioventricular Valves OpenOpen

2020

A-V valves close preventing backflow of blood A-V valves close preventing backflow of blood into atria into atria occurs when ventricles contract, pushing valve occurs when ventricles contract, pushing valve

cusps closed, chordae tendinae are pulled taut cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and and papillary muscles contract to pull cords and prevent cusps from evertingprevent cusps from everting

Atrioventricular Valves Atrioventricular Valves CloseClose

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Semilunar ValvesSemilunar Valves

SL valves open with ventricular contractionSL valves open with ventricular contraction allow blood to flow into pulmonary trunk and aortaallow blood to flow into pulmonary trunk and aorta

SL valves close with ventricular relaxationSL valves close with ventricular relaxation prevents blood from returning to ventricles, blood prevents blood from returning to ventricles, blood

fills valve cusps, tightly closing the SL valvesfills valve cusps, tightly closing the SL valves

2222

Which side is anterior surface?

What are the ventricles doing?

Valve Function ReviewValve Function Review

2323

Atria contract, blood fills ventricles through A-V valves

Ventricles contract, blood pumped into aorta and pulmonary trunk through SL valves

Valve Function ReviewValve Function Review

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Two closed circuits, the systemic and pulmonic Two closed circuits, the systemic and pulmonic Systemic circulationSystemic circulation

left side of heart pumps blood through bodyleft side of heart pumps blood through body left ventricle pumps oxygenated blood into aortaleft ventricle pumps oxygenated blood into aorta aorta branches into many arteries that travel to aorta branches into many arteries that travel to

organsorgans arteries branch into many arterioles in tissuearteries branch into many arterioles in tissue arterioles branch into thin-walled capillaries for arterioles branch into thin-walled capillaries for

exchange of gases and nutrientsexchange of gases and nutrients deoxygenated blood begins its return in venulesdeoxygenated blood begins its return in venules venules merge into veins and return to right atriumvenules merge into veins and return to right atrium

Blood CirculationBlood Circulation

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Pulmonary circulationPulmonary circulation right side of heart pumps deoxygenated blood to right side of heart pumps deoxygenated blood to

lungslungs right ventricle pumps blood to pulmonary trunkright ventricle pumps blood to pulmonary trunk pulmonary trunk branches into pulmonary arteriespulmonary trunk branches into pulmonary arteries pulmonary arteries carry blood to lungs for exchange pulmonary arteries carry blood to lungs for exchange

of gasesof gases oxygenated blood returns to heart in pulmonary veinsoxygenated blood returns to heart in pulmonary veins

Blood Circulation Blood Circulation (cont.)(cont.)

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Blood CirculationBlood Circulation

Blood flowBlood flow blue = deoxygenatedblue = deoxygenated red = oxygenatedred = oxygenated

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Coronary CirculationCoronary Circulation

Coronary circulation is blood supply to the Coronary circulation is blood supply to the heartheart

Heart as a very active muscle needs lots of OHeart as a very active muscle needs lots of O22

When the heart relaxes high pressure of blood When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels in aorta pushes blood into coronary vessels

Many anastomosesMany anastomoses connections between arteries supplying blood to connections between arteries supplying blood to

the same region, provide alternate routes if one the same region, provide alternate routes if one artery becomes occludedartery becomes occluded

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Coronary ArteriesCoronary Arteries Branches off aorta above Branches off aorta above

aortic semilunar valveaortic semilunar valve Left coronary arteryLeft coronary artery

circumflex branch circumflex branch in coronary sulcus, supplies in coronary sulcus, supplies

left atrium and left ventricleleft atrium and left ventricle anterior interventricular art.anterior interventricular art.

supplies both ventriclessupplies both ventricles Right coronary arteryRight coronary artery

marginal branchmarginal branch in coronary sulcus, supplies in coronary sulcus, supplies

right ventricleright ventricle posterior interventricular posterior interventricular

art.art. supplies both ventriclessupplies both ventricles

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Coronary VeinsCoronary Veins

Collects wastes from cardiac muscleCollects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart Drains into a large sinus on posterior surface of heart

called the coronary sinuscalled the coronary sinus Coronary sinus empties into right atriumCoronary sinus empties into right atrium

3030

Cardiac Muscle Cardiac Muscle HistologyHistology

Branching, intercalated discs with gap junctions, Branching, intercalated discs with gap junctions, involuntary, striated, single central nucleus per cellinvoluntary, striated, single central nucleus per cell

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Cardiac MyofibrilCardiac Myofibril

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Conduction System of Conduction System of HeartHeart

Coordinates contraction of heart muscle.

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Autorhythmic CellsAutorhythmic Cells Cells fire spontaneously, act as pacemaker and form Cells fire spontaneously, act as pacemaker and form

conduction system for the heartconduction system for the heart

SA nodeSA node cluster of cells in wall of Rt. Atriacluster of cells in wall of Rt. Atria begins heart activity that spreads to both atriabegins heart activity that spreads to both atria excitation spreads to AV nodeexcitation spreads to AV node

AV nodeAV node in atrial septum, transmits signal to bundle of Hisin atrial septum, transmits signal to bundle of His

AV bundle of His AV bundle of His the connection between atria and ventriclesthe connection between atria and ventricles divides into bundle branches & purkinje fibers, large divides into bundle branches & purkinje fibers, large

diameter fibers that conduct signals quicklydiameter fibers that conduct signals quickly

Conduction System of Conduction System of HeartHeart

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Rhythm of Conduction Rhythm of Conduction SystemSystem

SA node fires spontaneously 90-100 times per SA node fires spontaneously 90-100 times per minuteminute

AV node fires at 40-50 times per minuteAV node fires at 40-50 times per minute If both nodes are suppressed fibers in ventricles If both nodes are suppressed fibers in ventricles

by themselves fire only 20-40 times per minuteby themselves fire only 20-40 times per minute Artificial pacemaker needed if pace is too slowArtificial pacemaker needed if pace is too slow Extra beats forming at other sites are called Extra beats forming at other sites are called

ectopic pacemakersectopic pacemakers caffeine & nicotine increase activitycaffeine & nicotine increase activity

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Timing of Atrial & Timing of Atrial & Ventricular ExcitationVentricular Excitation

SA node setting pace since is the fastestSA node setting pace since is the fastest In 50 msec excitation spreads through both In 50 msec excitation spreads through both

atria and down to AV nodeatria and down to AV node 100 msec delay at AV node due to smaller 100 msec delay at AV node due to smaller

diameter fibers- allows atria to fully contract diameter fibers- allows atria to fully contract filling ventricles before ventricles contractfilling ventricles before ventricles contract

In 50 msec excitation spreads through both In 50 msec excitation spreads through both ventricles simultaneouslyventricles simultaneously

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Electrocardiogram---ECG or Electrocardiogram---ECG or EKGEKG

EKGEKG Action potentials of all Action potentials of all

active cells can be detected active cells can be detected and recorded and recorded

P waveP wave atrial depolarization atrial depolarization

P to Q intervalP to Q interval conduction time from atrial conduction time from atrial

to ventricular excitation to ventricular excitation QRS complex QRS complex

ventricular depolarizationventricular depolarization T waveT wave

ventricular repolarizationventricular repolarization

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One Cardiac CycleOne Cardiac Cycle

At 75 beats/min, one cycle requires 0.8 sec.At 75 beats/min, one cycle requires 0.8 sec. systole (contraction) and diastole (relaxation) of systole (contraction) and diastole (relaxation) of

both atria, plus the systole and diastole of both both atria, plus the systole and diastole of both ventriclesventricles

End diastolic volume (EDV)End diastolic volume (EDV) volume in ventricle at end of diastole, about volume in ventricle at end of diastole, about

130ml130ml End systolic volume (ESV)End systolic volume (ESV)

volume in ventricle at end of systole, about 60mlvolume in ventricle at end of systole, about 60ml Stroke volume (SV)Stroke volume (SV)

the volume ejected per beat from each ventricle, the volume ejected per beat from each ventricle, about 70mlabout 70ml

SV = EDV - ESVSV = EDV - ESV

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Phases ofPhases of Cardiac CycleCardiac Cycle Isovolumetric relaxationIsovolumetric relaxation

brief period when volume in ventricles does not brief period when volume in ventricles does not change--as ventricles relax, pressure drops and change--as ventricles relax, pressure drops and AV valves openAV valves open

Ventricular fillingVentricular filling rapid ventricular filling:as blood flows from full rapid ventricular filling:as blood flows from full

atriaatria diastasis: as blood flows from atria in smaller diastasis: as blood flows from atria in smaller

volumevolume atrial systole pushes final 20-25 ml blood into atrial systole pushes final 20-25 ml blood into

ventricleventricle Ventricular systoleVentricular systole

ventricular systoleventricular systole isovolumetric contractionisovolumetric contraction

brief period, AV valves close before SL valves open brief period, AV valves close before SL valves open ventricular ejection: as SL valves open and blood ventricular ejection: as SL valves open and blood

is ejectedis ejected

3939

Ventricular PressuresVentricular Pressures

Blood pressure in aorta is 120mm HgBlood pressure in aorta is 120mm Hg Blood pressure in pulmonary trunk is 30mm HgBlood pressure in pulmonary trunk is 30mm Hg Differences in ventricle wall thickness allows Differences in ventricle wall thickness allows

heart to push the same amount of blood with heart to push the same amount of blood with more force from the left ventriclemore force from the left ventricle

The volume of blood ejected from each ventricle The volume of blood ejected from each ventricle is 70ml (stroke volume) is 70ml (stroke volume)

Why do both stroke volumes need to be same?Why do both stroke volumes need to be same?

4040

AuscultationAuscultation

StethoscopeStethoscope Sounds of heartbeat are from Sounds of heartbeat are from

turbulence in blood flow caused by turbulence in blood flow caused by valve closurevalve closure first heart sound (lubb) is created with the first heart sound (lubb) is created with the

closing of the atrioventricular valvesclosing of the atrioventricular valves second heart sound (dupp) is created with second heart sound (dupp) is created with

the closing of semilunar valvesthe closing of semilunar valves

4141

Heart SoundsHeart Sounds

Where to listen on chest wall for heart sounds.

4242

Cardiac OutputCardiac Output

Amount of blood pushed into aorta or Amount of blood pushed into aorta or pulmonary trunk by ventriclepulmonary trunk by ventricle

Determined by stroke volume and heart rateDetermined by stroke volume and heart rate CO = SV x HRCO = SV x HR

at 70ml stroke volume & 75 beat/min----5 and at 70ml stroke volume & 75 beat/min----5 and 1/4 liters/min1/4 liters/min

entire blood supply passes through circulatory entire blood supply passes through circulatory system every minutesystem every minute

Cardiac reserve is maximum output/output Cardiac reserve is maximum output/output at restat rest average is 4-5 while athlete is 7-8average is 4-5 while athlete is 7-8

4343

Influences on Stroke Influences on Stroke VolumeVolume Preload (affect of stretching)Preload (affect of stretching)

Frank-Starling Law of HeartFrank-Starling Law of Heart more muscle is stretched, greater force of more muscle is stretched, greater force of

contractioncontraction more blood more force of contraction resultsmore blood more force of contraction results

ContractilityContractility autonomic nerves, hormones, Ca+2 or K+ levelsautonomic nerves, hormones, Ca+2 or K+ levels

AfterloadAfterload amount of pressure created by the blood in the amount of pressure created by the blood in the

wayway high blood pressure creates high afterloadhigh blood pressure creates high afterload

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Congestive Heart Failure Congestive Heart Failure

Causes of CHFCauses of CHF coronary artery disease, hypertension, MI, valve coronary artery disease, hypertension, MI, valve

disorders, congenital defectsdisorders, congenital defects Left side heart failureLeft side heart failure

less effective pump so more blood remains in less effective pump so more blood remains in ventricleventricle

heart is overstretched & even more blood heart is overstretched & even more blood remainsremains

blood backs up into lungs as pulmonary edemablood backs up into lungs as pulmonary edema suffocation & lack of oxygen to the tissuessuffocation & lack of oxygen to the tissues

Right side failure Right side failure fluid builds up in tissues as peripheral edemafluid builds up in tissues as peripheral edema

4545

Risk Factors for Heart Risk Factors for Heart DiseaseDisease

Risk factors in heart disease: Risk factors in heart disease: high blood cholesterol levelhigh blood cholesterol level high blood pressurehigh blood pressure cigarette smokingcigarette smoking obesity & lack of regular exercise.obesity & lack of regular exercise.

Other factors include:Other factors include: diabetes mellitusdiabetes mellitus genetic predispositiongenetic predisposition male gendermale gender high blood levels of fibrinogenhigh blood levels of fibrinogen left ventricular hypertrophyleft ventricular hypertrophy

4646

Plasma Lipids and Plasma Lipids and Heart DiseaseHeart Disease

Risk factor for developing heart disease is Risk factor for developing heart disease is high blood cholesterol level.high blood cholesterol level. promotes growth of fatty plaques promotes growth of fatty plaques Most lipids are transported as lipoproteinsMost lipids are transported as lipoproteins

low-density lipoproteins (LDLs)low-density lipoproteins (LDLs) high-density lipoproteins (HDLs)high-density lipoproteins (HDLs) very low-density lipoproteins (VLDLs)very low-density lipoproteins (VLDLs)

HDLs remove excess cholesterol from circulationHDLs remove excess cholesterol from circulation LDLs are associated with the formation of fatty LDLs are associated with the formation of fatty

plaques plaques VLDLs contribute to increased fatty plaque VLDLs contribute to increased fatty plaque

formationformation There are two sources of cholesterol in the There are two sources of cholesterol in the

body:body: in foods we ingest & formed by liverin foods we ingest & formed by liver

4747

Desirable Levels of Desirable Levels of Blood Cholesterol for Blood Cholesterol for AdultsAdults

TC (total cholesterol) under 200 mg/dlTC (total cholesterol) under 200 mg/dl LDL under 130 mg/dlLDL under 130 mg/dl HDL over 40 mg/dlHDL over 40 mg/dl Normally, triglycerides are in the range of Normally, triglycerides are in the range of

10-190 mg/dl.10-190 mg/dl. Among the therapies used to reduce Among the therapies used to reduce

blood cholesterol level are exercise, diet, blood cholesterol level are exercise, diet, and drugs.and drugs.

4848

Exercise and the HeartExercise and the Heart

Sustained exercise increases oxygen Sustained exercise increases oxygen demand in muscles.demand in muscles.

Benefits of aerobic exercise (any activity Benefits of aerobic exercise (any activity that works large body muscles for at least that works large body muscles for at least 20 minutes, preferably 3-5 times per 20 minutes, preferably 3-5 times per week) are;week) are; increased cardiac outputincreased cardiac output increased HDL and decreased triglyceridesincreased HDL and decreased triglycerides improved lung functionimproved lung function decreased blood pressuredecreased blood pressure weight control.weight control.

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Coronary Artery DiseaseCoronary Artery Disease Heart muscle Heart muscle

receiving insufficient receiving insufficient blood supplyblood supply narrowing of narrowing of

vessels---vessels---atherosclerosis, atherosclerosis, artery spasm or clotartery spasm or clot

atherosclerosis--atherosclerosis--smooth muscle & smooth muscle & fatty deposits in walls fatty deposits in walls of arteriesof arteries

TreatmentTreatment drugs, bypass graft, drugs, bypass graft,

angioplasty, stentangioplasty, stent

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Clinical ProblemsClinical Problems MI = myocardial infarctionMI = myocardial infarction

death of area of heart muscle from lack of Odeath of area of heart muscle from lack of O22

replaced with scar tissuereplaced with scar tissue results depend on size & location of damageresults depend on size & location of damage

Blood clotBlood clot use clot dissolving drugs streptokinase or t-PA use clot dissolving drugs streptokinase or t-PA

& heparin& heparin balloon angioplastyballoon angioplasty

Angina pectoris----heart pain from ischemia Angina pectoris----heart pain from ischemia of cardiac muscleof cardiac muscle

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By-pass GraftBy-pass Graft

5252

Percutaneous Percutaneous Transluminal Coronary Transluminal Coronary AngioplastyAngioplasty

5353

Stent in an ArteryStent in an Artery

Maintains patency of blood vesselMaintains patency of blood vessel