Transcript Cardiovascular System: The Heart

Cardiovascular System: The Heart
Dr. Michael P. Gillespie
Cardiovascular System
 Blood
 Heart
 Blood vessels
Heart
 Propels the blood through the blood vessels
to reach all of cells of the body.
 It circulates the blood through an estimated
100,000 km (60,000 miles) of blood vessels.
Heart
 It beats 100,000 times every day (35 million
beats / year).
 It pumps about 5 liters (5.3 qt) each minute
and 14,000 liters (3,600 gal) each day.
 Cardiology – the study of the normal heart
and diseases associated with it.
Size And Shape
 About the size of a closed fist.
 Cone-shaped.
 12cm (5 in.) Long, 9cm (3.5 in.) Wide, and
6cm (2.5 in.) Thick.
 250g (8 oz) in adult females and 300g (10
oz) in adult males.
Location
 Lies in the mediastinum (a mass of tissue
between the sternum and the vertebral
column).
 2/3 of the mass is left of midline.
 A cone lying on its side.
Anatomical Landmarks
 The apex (pointed end) is directed anteriorly,
inferiorly, and to the left.
 The base (broad portion) is directed
posteriorly, superiorly, and to the right.
 Anterior surface – deep to sternum & ribs.
Anatomical Landmarks
 Inferior surface – rests upon diaphragm.
 Right border – faces the right lung.
 Left border (pulmonary border) – faces the
left lung.
Cardiopulmonary Resuscitation
(CPR)
 External pressure (compression) can be used to
force blood out of the heart and into the circulation.
 CPR is utilized when the heart suddenly stops
beating.
 Cardiac compressions with artificial ventilation of
the lungs keeps oxygenated blood circulating until
the heart can be restarted.
 Self CPR (coughing).
Pericardium
 Pericardium – membrane that surrounds and
protects the heart.
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Fibrous pericardium – tough, inelastic, dense irregular
CT. Prevents overstretching of the heart.
Serous pericardium – thinner, more delicate layer.
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Parietal layer.
Visceral layer (epicardium) – adheres to the heart.
Pericardial fluid lies in between these two layers in the
pericardial cavity.
Layers Of The Heart Wall
 Epicardium (visceral layer of the serous
pericardium).
 Myocardium – cardiac muscle tissue.
 Endocardium – smooth lining of the
chambers of the heart and valves (continuous
with blood vessels).
Chambers Of The Heart
 Atria – superior chambers.
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Auricle – pouchlike structure.
 Ventricles – inferior chambers.
 Sulci – grooves on the surface of the heart
that contain blood vessels.
Chambers Of The Heart
 Right atrium – receives blood from three
veins: superior vena cava, inferior vena
cava, and coronary sinus.
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Tricuspid valve.
Pectinate muscles.
Interatrial septum.
Fossa ovalis – depression (remnant of foramen
ovale).
Chambers Of The Heart
 Right ventricle – receives blood from right atrium.
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Trabeculae carneae – bundles of cardiac muscle tissue.
Chordae tendineae – connects to the cusps of the
tricuspid valve which are connected to papillary muscles.
Interventricular septum.
Pulmonary valve into pulmonary arteries.
Chambers Of The Heart
 Left atrium – receives blood from the lungs through
the pulmonary veins.
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Bicuspid (mitral) valve.
 Left ventricle – receives blood from left atrium.
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Trabeculae carneae – bundles of cardiac muscle tissue.
Chordae tendineae – connects to the cusps of the
bicuspid valve which are connected to papillary muscles.
Aortic valve into the ascending aorta (largest artery).
Myocardial Thickness
 The function of the individual chambers
determines their thickness.
 The atria pump blood a short distance and
consequently have thinner walls than the
ventricles.
 The left ventricle pumps blood a greater
distance than the right at higher pressures
and has a thicker wall.
Fibrous Skeleton Of The Heart
 Dense CT rings that surround the valves and
prevent overstretching.
 Provides insertion points for bundles of
cardiac muscle fibers.
Atrioventricular (AV) Valves
 Tricuspid and bicuspid valves.
 When the valve is open, the pointed cusps
point into the ventricle.
Atrioventricular (AV) Valves
 When atrial pressure is higher than ventricular
pressure the valves open (the papillary muscles are
relaxed and the chordae tendinae is slack.
 When the ventricles contract the pressure forces the
AV valves closed. The papillary muscles close
concurrently.
 Damaged valves allow regurgitation (flow back).
Semilunar (SL) Valves
 The aortic and pulmonary valves.
 The SL valves open when the pressure in the
ventricles exceeds the pressure in the
arteries.
Heart Valve Disorders
 Stenosis (narrowing) – failure of the heart
valve to open fully.
 Insufficiency (incompetence) – failure of a
valve to close fully.
 Mitral stenosis – due to scar formation of a
congenital defect.
Heart Valve Disorders
 Mitral insufficiency – backflow of blood
from the left ventricle to the left atrium.
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Mitral valve prolapse (MVP) – one or both cusps
protrude into the left atrium during ventricular
contraction.
 Aortic stenosis – the aortic valve is
narrowed.
Heart Valve Disorders
 Aortic insufficiency – backflow of blood
from the aorta into the left ventricle.
 Rheumatic fever – an acute systemic
inflammatory disease. Antibodies produced
to destroy the bacteria attack and inflame the
CT of joints, heart valves and other organs.
Systemic And Pulmonary
Circulations
 Two closed systems.
 The output of one becomes the input of
another with each beat of the heart.
Coronary Circulation
 The myocardium has its own blood vessels, the
coronary circulation.
 The coronary arteries branch from the ascending
aorta and encircle the heart.
 When the heart is contracting the coronary arteries
are squeezed shut.
 When the heart is relaxed, the high pressure from
the aorta pushes blood into the coronary arteries
and from the arteries to the coronary veins.
Coronary Arteries
 Two coronary arteries, right and left
coronary arteries, branch from the ascending
aorta and supply oxygenated blood to the
myocardium.
Coronary Arteries
 Left coronary artery branches into:
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Anterior interventricular or left anterior
descending LAD (supplies ventricle walls).
Circumflex branches (supplies left ventricle and
left atrium).
Coronary Arteries
 Right coronary artery branches into:
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Atrial branches (supplies right atrium).
Posterior interventricular branch (supplies the
two ventricles).
Right marginal branch (supplies the right
ventricle).
Coronary Veins
 The great cardiac vein (anterior) and the
middle cardiac vein (posterior) drain into the
coronary sinus.
 Coronary Sinus – a large bascular sinus on
the posterior surface of the heart.
Reperfusion Damage
 Reperfusion is reestablishing the blood flow
to the heart muscle after a blockage of a
coronary artery.
 Reperfusion damages the tissue further due
to the formation of oxygen free radicals from
the reintroduced oxygen.
Histology Of Cardiac Muscle
Tissue
 Cardiac muscle fibers are shorter in length
and less circular than skeletal muscle fibers.
 Cardiac muscle fibers exhibit branching.
Histology Of Cardiac Muscle
Tissue
 Usually one centrally located nucleus is present,
although it may occasionally have two nuclei.
 Intercalated disc connect neighboring fibers.
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The discs contain desmosomes, which hold the fibers
together.
 Mitochondria are larger and more numerous in
cardiac muscle fiber.
 Gap junctions allow for propagation of action
potentials.
Regeneration Of Heart Cells
 Infarcted (dead) cardiac muscle tissue is
replaced with non-contractile fibrous scar
tissue.
 A lack of stem cells limits the ability of the
heart to repair damage.
 Some stem cells from the blood migrate into
the heart tissues and differentiate into
functional muscle cells and endothelial cells.
Autorhythmic Fibers: The
Conduction System
 Autorhythmic fibers are self-excitable and
maintain the heart’s continuous beating.
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Act as a pacemaker, setting the rhythm of
electrical excitation that causes contraction of a
heart.
Form a conduction system, that provides a path
for the cycle of cardiac excitation through the
heart.
Sequence Of Cardiac
Conduction
 Sinoatrial (SA) node – undergo spontaneous
depolarization (pacemaker potential) –
propagates through the atria through gap
junctions.
 Atrioventricular (AV) node (bundle of his) –
site where action potentials are conducted
from the atria to the ventricles.
Sequence Of Cardiac
Conduction
 Right and left bundle branches – propagate
action potentials through the ventricles and
the interventricular septum to the apex of the
heart.
 Purkinje fibers – conduct the action
potentials from the apex, through the
remainder of the ventricles stimulating
contraction.
Pacemaker
 The SA node regulates the pace of the heart.
 At rest, it contracts approximately 100 time
per minute.
 Nerve impulses from the ANS and blood
born hormones (epinephrine) modify the
timing and strength of each heartbeat.
Pacemaker
 Acetylcholine from the ANS slows the heart
rate to about 75 bpm.
 If the SA node becomes damaged, the AV
node can pick up the job; However, at a
slower rate (40 – 60 bpm).
 If both nodes are damaged, an artificial
pacemaker sends out electrical currents to
stimulate the heart to contract.
Ectopic Pacemaker
 If a site other than the SA node becomes selfexcitable, it becomes an ectopic pacemaker.
 It make operate occasionally, producing extra
beats, or for a period of time.
 Triggers:
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Caffeine, nicotine, electrolyte imbalances,
hypoxia, and toxic reactions to drugs.
Refractory Period
 In cardiac muscle tissue, the refractory
period lasts longer than the contraction
period.
 This prevents tetanus (maintained
contraction).
Electrocardiogram (ECG or
EKG)
 As action potentials propagate through the
heart, they generate electrical currents that
can be detected on the surface of the body.
 An electrocardiogram is a recording of these
signals.
 An electrocardiograph is the instrument used
to record the signals.
Electrocardiogram (ECG or
EKG)
 Electrodes are positioned on the arms and
legs (limb leads) and at six positions on the
chest (chest leads).
 12 different tracings are produced from
different combinations of leads.
Electrocardiogram (ECG or
EKG)
 If these tracings are compared to one another
and to a normal tracing, it is possible to
determine the following:
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If the conducting pathway is abnormal.
If the heart is enlarged.
If certain regions of the heart are damaged.
Typical Lead II Record
 Three clearly recognizable waves appear
with each heartbeat.
 P wave – atrial depolarization.
 QRS complex – rapid ventricular
depolarization.
 T wave – ventricular repolarization.
Changes In Wave Size
 Large P waves – enlargement of the atrium.
 Large Q waves – myocardial infarction.
 Large R waves – enlarged ventricles.
 Flat T wave – insufficient oxygen.
 Large T wave – hyperkalemia (high blood
K+ levels).
Stress Electrocardiogram
(Stress Test)
 Elevate the heart’s response to stress.
 Narrowed coronary arteries may carry
adequate blood supply at rest, but not during
exercise.
Changes In Time Span
Between Waves
 Time spans between waves are called intervals or
segments.
 P-Q interval – time between the beginning of the P
wave and the beginning of the QRS complex.
 The P-Q interval represents the time required for an
action potential to travel through the atria, AV node
and remaining fibers of the conduction system.
Changes In Time Span
Between Waves
 The P-Q interval lengthens when the action
potentials must travel around scar tissue from
rheumatic fever.
 The S-T segement is elevated in acute myocardial
infarction and depressed when the heart receives
insufficient oxygen.
 The Q-T interval may be lengthened by myocardial
damage, myocardial ischemia, or conduction
abnormalities.
Terminology
 Systole – the phase of contraction.
 Diastole – the phase of relaxation.
 Cardiac cycle – all of the events associated
with one heartbeat (systole and diastole of
the atria and systole and diastole of the
ventricles).
Heart Sounds
 Auscultation – listening to sounds within the
body (performed with a stethoscope).
 During each cardiac cycle there are 4 heart
sounds, but in a normal heart, only the first
and second heart sounds (S1 and S2) are loud
enough to be heard with a stethoscope.
Heart Sounds
 The first sound (S1), described as a lubb
sound, is louder and longer than the second.
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Caused by closure of the AV valves after
ventricular systole begins.
 The second sound (S2), described as dupp
sound, is shorter and not as loud as S1.
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Caused by closure of the semilunar valves as
ventricular diastole begins.
Heart Sounds
 S3 is due to blood turbulence from rapid
ventricular filling.
 S4 is due to blood turbulence during atrial
systole.
 S3 and S4 are not normally heard.
Heart Murmurs
 A heart murmur is an abnormal sound
consisting of a clicking, rushing, or gurgling
noise that is heard before, between, or after
the normal heart sounds. It can also mask the
normal heart sounds.
 Some heart murmurs are “innocent”;
However, they usually represent a valve
disorder.
Congestive Heart Failure
 In CHF, the heart is a failing pump.
 Causes include coronary artery disease,
congenital defects, long-term high blood
pressure (increases afterload), myocardial
infarctions, valve disorders.
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Pulmonary edema – left ventricle fails first.
Peripheral edema – right ventricle fails first.
Regulation Of Heart Rate
 Autonomic regulation of heart rate.
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Proprioceptors, chemoreceptors, baroreceptors.
Cardiac accelerator nerves.
 Chemical regulation of heart rate.
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Hormones (epinephrine, norepinephrine, and
thyroid hormones) accelerate the heart rate.
Cations.
Terminology
 Tachycardia – elevated resting heart rate.
 Bradycardia – a resting heart rate under 60
bpm.
 Hypothermia – lowering of the body
temperature, which slows the heart rate.
Disorders Of The Heart
 Coronary artery disease (CAD).
 Arteriosclerosis and atherosclerosis.
Disorders Of The Heart
 Myocardial ischemia and infarction.
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Hypoxia.
Angina pectoris.
Disorders Of The Heart
 Congenital defects.
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Coarctation of the aorta.
Patent ductus arteriosus.
Septal defect.
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Atrial and ventricular.
Tetralogy of Fallot.
Disorders Of The Heart
 Arrhythmias – irregularity of the heart
rhythm.
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Heart block.
Flutter and fibrillation.
Ventricular premature contraction.
Medical Terminology
 Angiocardiography – x-ray examination of the heart
and great vessels with radiopaque dye.
 Cardiac arrest.
 Cardiomegaly.
 Cor pulmonale (CP) – ventricular hypertrophy from
disorders that bring about hypertension in the
pulmonary circulation.
 Palpitation.