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Rob Swatski Associate Professor of Biology
HACC – York Campus
Chapter 20
Cardiovascular System: The Heart
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(a) Inferior view of transverse section of thoracic cavity showing heart in mediastinum
Sternum
Muscle
Left lung
Esophagus Sixth thoracic vertebra
LEFT PLEURAL CAVITY
Heart
PERICARDIAL CAVITY
Right lung
Aorta RIGHT PLEURAL CAVITY
POSTERIOR
ANTERIOR
View
Transverse plane
Pulmonary trunk (artery)
Heart LocaEon: MediasEnum
Arch of aorta
Anterior view of heart in thoracic cavity
Pulmonary trunk
Left lung
LEFT SURFACE
APEX OF HEART
Superior vena cava
RIGHT SURFACE
Right lung
Pleura (cut to reveal lung inside)
Diaphragm
INFERIOR SURFACE
Heart
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Heart OrientaEon
Apex: anteriorly, inferiorly, le6-‐side Base: posteriorly, superiorly, right-‐side Anterior surface: deep to sternum & ribs Inferior surface: on diaphragm Right border: faces right lung LeK (Pulmonary) border: faces le6 lung
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Heart Surface ProjecEon
Superior right point: sup border -‐ 3rd right costal carClage
Superior leK point: inf border -‐ 2nd le6 costal carClage, 3 cm le6 of midline
Inferior leK point: 5th intercostal space, 9 cm le6 of midline
Inferior right point: sup border -‐ 6th right costal carClage, 3 cm right of midline
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Pericardium
Fibrous pericardium (outer) -‐ dense irregular CT -‐ protects & anchors heart -‐ prevents overstretching
Serous pericardium (epicardium): -‐ thin, delicate membrane -‐ parietal & visceral layers -‐ pericardial cavity -‐ pericardial fluid
PericardiEs
Cardiac tamponade
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Layers of the Heart Wall Epicardium: 2 layers – 1) visceral layer of serous pericardium & 2)
adipose Cssue & fibroelasCc Cssue
Myocardium: cardiac muscle
Endocardium: endothelium & CT (lines chambers & valves)
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Muscle Bundles of the Myocardium
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MyocardiEs & EndocardiEs
endocardiEs myocardiEs
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Chambers & Sulci of the Heart
4 Chambers: -‐ 2 superior atria
-‐ 2 inferior ventricles
Sulci: grooves on heart surface -‐ contain coronary BVs & adipose
Coronary sulcus -‐ encircles heart b/w atria & ventricles
Anterior interventricular sulcus -‐ ant. boundary b/w ventricles
Posterior interventricular sulcus -‐ post. boundary b/w ventricles
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Right Atrium
Receives blood from 3 sources: superior vena cava, inferior vena cava, & coronary sinus
Interatrial septum
Fossa ovalis: remnant of fetal foramen ovale
Tricuspid valve -‐ blood flows through into right ventricle -‐ 3 cusps of dense CT -‐ “RAT on the Right” (Right Atrioventricular, Tricuspid)
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Right Ventricle
Forms most of ant. surface of heart
Interventricular septum
Trabeculae carneae
Papillary muscles
Chordae tendineae
Pulmonary semilunar valve -‐ allows blood into pulmonary trunk
Papillary Muscles & Chordae Tendineae
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LeK Atrium
Forms most of base of heart Receives blood from lungs through 4 pulmonary veins -‐ 2 right & 2 le6 Bicuspid valve: blood flows through into le6 ventricle -‐ 2 cusps -‐ “LAMB on the Le6”: Le6 Atrioventricular, Mitral, or Bicuspid
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LeK Ventricle
Forms apex of heart Chordae tendineae, papillary muscles, & trabeculae carneae
AorEc semilunar valve -‐ allows blood into ascending aorta -‐ openings to the coronary arteries directly above valve
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Myocardial Thickness & FuncEon Thickness varies based on each chamber’s funcCon:
-‐ Atria walls are thin; Ventricle walls are thick -‐ Right ventricle walls are thin; LeK ventricle walls are
thick
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Fibrous Skeleton of Heart
Dense CT rings surround heart valves -‐ fuse together & merge with interventricular septum
FuncEons of fibrous skeleton: -‐ valve support structure
-‐ Prevents overstretching of the valves -‐ inserCon point for cardiac muscle bundles -‐ electrical insulator b/w atria & ventricles
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AV Valves OPEN
Allow blood flow from atria into ventricles when ventricular pressure is lower than
atrial pressure Occurs during ventricular relaxaEon:
-‐ papillary muscles are relaxed -‐ chordae tendineae are slack
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AV Valves CLOSED
Prevents backflow (regurgita/on) of blood into atria
Occurs during ventricular contracEon: -‐ papillary muscles contract -‐ chordae tendineae pulled taut -‐ valve cusps pushed closed
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SL valves OPEN during ventricular contracCon -‐ allow blood flow into pulmonary trunk & aorta
SL valves CLOSE during ventricular relaxaCon -‐ blood fills cusps & valves close
-‐ prevents blood from flowing backwards into ventricles
Semilunar Valves
Superior view with atria removed: pulmonary and aortic valves closed, bicuspid and
tricuspid valves open
PULMONARY VALVE (closed)
Left coronary artery
BICUSPID VALVE (open)
TRICUSPID VALVE (open)
AORTIC VALVE (closed)
Right coronary artery
POSTERIOR
ANTERIOR
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Heart Valve Disorders Stenosis: narrowing of valve that restricts blood flow
-‐ Surgically repaired or replaced with mechanical valves or valves from human donors or pigs
Insufficiency or incompetence: valve cannot close completely
Balloon valvuloplasty
Mitral Valve Stenosis 35
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Systemic CirculaEon
LEFT side of heart pumps oxygenated blood to body
LeK atrium à LeK ventricle à Aorta à Systemic arteries à Arterioles à Systemic capillaries à Organsà Systemic venules à Systemic veins à Superior/Inferior vena
cava/Coronary sinus à Right atrium
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Pulmonary CirculaEon
RIGHT side of heart pumps deoxygenated blood to lungs
Right atrium à Right ventricle à Pulmonary trunk à Pulmonary arteries à Pulmonary capillaries à Lungs à Pulmonary Veins
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Oxygen-rich blood
Path of blood flow through heart
Oxygen-poor blood
10. 8.
5.
7.
2.
1.
3.
5.
6.
10.
4. Pulmonary capillaries of right lung
Key:
4. Pulmonary capillaries of left lung
9. Systemic capillaries of head and upper limbs
9. Systemic capillaries of trunk and lower limbs
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Coronary CirculaEon
Blood flow into the myocardium
Supplies the cardiac muscle Cssue of the heart wall
Many anastomoses
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Coronary Arteries
Right coronary artery
Marginal branch Posterior interventricular branch
LeK coronary artery
Anterior interventricular branch
or Le6 anterior descending (LAD)
Circumflex branch
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Coronary Veins
Collect wastes from myocardium
Great cardiac vein, Middle cardiac vein, Small cardiac vein, Anterior cardiac vein
Drain into coronary sinus
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Cardiac Muscle Tissue
Striated, branching,
shorter fibers of heart
Intercalated discs with gap juncEons
One central nucleus per fiber
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Cardiac Muscle Histology
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Cardiac Muscle Tissue
Same acCn & myosin
arrangement as skeletal muscle
Autorhythmic
Longer contracCons (longer Ca+2 delivery)
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Cardiac Myofibril
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ConducEon System
Autorhythmic fibers à
spontaneous APs
Propagate APs through
myocardium
Sinoatrial (SA) node =
pacemaker
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SA node
AV node
AV bundle (of His)
Right & leK bundle branches
Purkinje fibers
ConducEon System
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RegulaEon of the ConducEon System
Autonomic Nervous System
(ANS)
Hormones (epinephrine)
Modify heart rate & strength of contracCon
They do NOT establish the fundamental
rhythm
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AcEon PotenEal
DepolarizaEon
Plateau
RepolarizaEon
Refractory period
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Physiology of ContracEon
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Electro-‐cardiogram (ECG or EKG)
Visual record of all APs during each cardiac cycle (heartbeat)
Detected at body’s surface
DiagnosCc value
Detects abnormal conducCon,
enlargement, muscle damage, & reasons for
chest pain
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ECG
P wave
QRS complex
T wave
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DiagnosEc Value of the ECG
P-‐Q interval
S-‐T segment
Q-‐T interval
Ventricular diastole (relaxation)
6 Repolarization of ventricular contractile fibers produces T wave
5 Ventricular systole (contraction)
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Depolarization of ventricular contractile fibers produces QRS complex
3 Atrial systole (contraction)
2 Depolarization of atrial contractile fibers produces P wave
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Action potential in SA node
P P P
P P P
R
Q S
T
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Cardiac Cycle
Systole = ContracCon Diastole = RelaxaCon
At 75 beats/min, 1 cycle = 0.8 sec
Pressure & volume changes during
cycle
Blood pumped from high to low pressure areas
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Atrial systole (contrac'on)
Atrial diastole (relaxa'on)
Ventricular systole
Ventricular diastole
Cardiac Cycle
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Blood Volumes
End Diastolic Volume (EDV)
= 130 ml
End Systolic Volume (ESV)
= 60 ml
Stroke Volume (SV)
= 70 ml
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SV = EDV -‐ ESV
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Phases of the Cardiac Cycle
Isovolumetric RelaxaEon
(all valves close)
Ventricular Filling
(AV valves open)
Isovolumetric ContracEon
(AV valves close)
Ventricular EjecEon
(SL valves open)
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Ventricular Pressures
AorCc BP = 120 mmHg
Pulmonary trunk BP = 30 mmHg
Why? How?
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Heart Sounds
AuscultaEon
Produced when valves close
S1: “lubb” = AV valves close (louder, longer)
S2: “dupp” = SL valves close (quiet, shorter)
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Heart Sounds
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Heart Murmurs
Abnormal sounds before, b/w, or a6er normal sounds
May also mask normal sounds
Caused by valve disorders (stenosis,
incompetency)
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Cardiac Output Volume of blood ejected each
minute from either ventricle
CO = Stroke Volume (SV) x Heart Rate (HR)
70 ml SV x 75 beats/min = 5.25 L/min
Cardiac reserve
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RegulaEon of Stroke Volume
Preload
ContracElity
AKerload
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Preload The greater the stretch, the
greater the force of contracCon
The greater the blood volume, the greater the force of contracCon
Frank-‐Starling Law of the Heart
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ContracElity
PosiEve inotropic agents
SCmulaCon of he SympatheCc division of the Autonomic Nervous
System (ANS)
Hormones: epinephrine & norepinephrine
Higher intersCCal Ca+2
Drugs (digitalis)
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ContracElity
NegaEve inotropic agents
InhibiCon of the SympatheCc division of the Autonomic Nervous
System (ANS)
Anoxia, acidosis, some anestheCcs
Higher intersCCal K+
Drugs (Calcium channel blockers)
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AKerload
The back pressure in the arteries that
the ventricles must overcome…
…in order to open the semilunar
valves
The greater the BP = the greater the a6erload
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CongesEve Heart Failure
If a6erload is high, more blood remains in the ventricles…
…which increases the preload
Le? ventricular failure = pulmonary
edema
Right ventricular failure = peripheral
edema
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Neural RegulaEon of Heart Rate
Cardiovascular center in medulla
oblongata
SympatheEc impulses increase HR & force of contracCon
ParasympatheEc impulses
decrease HR
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Nervous System
Receptors
Proprioceptors: monitor
movements
Chemoreceptors: monitor blood chemistry
Baroreceptors: monitor BP
Cardiovascular (CV) center
Key: Sensory (afferent) neurons Motor (efferent) neurons
Medulla oblongata
Glossopharyngeal nerves (cranial nerve IX)
Vagus nerves (cranial nerve X, parasympathetic)
SA node
Sympathetic trunk ganglion
Cardiac accelerator nerve (sympathetic)
Ventricular myocardium
AV node
Baroreceptors in arch of aorta
Baroreceptors in carotid sinus
Spinal cord
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Biochemical RegulaEon of Heart Rate
Oxygen level: hypoxia
pH: acidosis and alkalosis
Hormones: Epinephrine, norepinephrine, thyroid
hormones
CaEons: Na+, K+, Ca+2
Other factors: Age, gender, physical fitness, body temperature, stress
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High blood cholesterol High BP Smoking
Obesity Lack of regular exercise
Family history
Male gender Diabetes Le6
ventricular hypertrophy
Risk Factors for Heart Disease
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Plasma Lipids & Heart Disease High blood cholesterol:
promotes plaques
High-‐Density Lipoproteins
(HDLs)
Low-‐Density Lipoproteins
(LDLs)
Very Low-‐Density Lipoproteins
(VLDLs)
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Coronary Artery Disease (CAD)
Ischemia
Reduced blood flow through
coronary arteries
Causes hypoxia & weakens
cardiac muscle
Angina Pectoris
Narrowing of coronary arteries
Leads to reduced blood flow, chest pain, pressure, discomfort
Myocardial InfarcEon
Complete obstrucCon of coronary blood
flow causing heart amack
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Coronary Artery Disease ObstrucEons
Atherosclerosis
Coronary artery spasm
Coronary artery thrombosis
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Coronary Artery Bypass GraKing (CABG)
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Congenital Heart Defects
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Congenital Heart Defects, cont.
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Arrhythmia
Irregularity in heart rhythm due to
conducCon system defect
Bradycardia
Tachycardia
FibrillaEon
(d) Ventricular tachycardia
Ventricular fibrillation
(e) Ventricular fibrillation
Ventricular tachycardia
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