Download The Heart

The Heart
Cardiology
Physical Characteristics
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Situated between the lungs in the
mediastinum
About the size of a clenched fist
Cone or pyramid shape, tilting to the
left
Apex - inferior portion
Base - superior portion
Pericardium - 3 layers
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Fibrous pericardium - outer layer
Serous pericardium - inner layer
 parietal layer
 visceral layer (epicardium)
Pericardial cavity - space between the
parietal and visceral layers that is filled
with pericardial fluid
Pericardial fluid - lubrication,reduces
friction
Heart Wall
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Epicardium - outermost layer
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visceral pericardium
Myocardium - middle layer
cardiac muscle
 involuntary, striated, short, branched cells
 intercalated discs
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Endocardium - inner layer
lines the chambers and covers the valves
 simple squamous epithelium
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Heart Chambers
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Two upper atria ; two lower ventricles
Atria are the receiving chambers
Ventricles are the distributing chambers
Interatrial septum separates atria
Interventricular septum divides
ventricles
Auricles are external flaps
Left ventricle very thick
Heart Valves
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Atrioventricular valves
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tricuspid (right)
bicuspid or mitral (left)
chordae tendineae
papillary muscle
Semilunar valves
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aortic semilunar
pulmonary semilunar
three pocketlike cusps
Valve Disorders
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Rheumatic Fever - group A, B-hemolytic
Streptococcus pyogenes
Heart Mumur
 stenosis
 incompetent valves
 Mitral valve prolapse (MVP)
Blood Flow through the Heart
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The heart receives blood from the superior
vena cava, inferior vena cava and the coronary
sinus
Right atrium->tricuspid valve->right ventricle->
pulmonary semilunar valve-> pulmonary
trunk>pulmonary arteries-> lungs-> pulmonary
veins->left atrium->mitral valve->left
ventricle>aortic semilunar valve -> aorta
Pulmonary & Systemic
Circulation
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Pulmonary circulation - refers to blood
going through the right side of the
heart to the lungs
Systemic circulation - involves the left
heart. Oxygenated blood from the lungs
flows into the left atrium, enters the left
ventricle, out through the aorta into the
body’s tissue, and back via systemic
veins to the right atrium
Coronary Circulation
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The aorta branches
into the left and
right coronary
arteries
Blood flow through myocardium
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Left coronary artery
 Anterior interventricular artery
 Circumflex artery
Right coronary artery
 Posterior interventricular artery
 Marginal artery
Arterial anastomoses
Venous Drainage
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Great cardiac veins
Coronary sinus
Right atrium
Cardiac Conduction System
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Sinoatrial (SA) node
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Pacemaker of the heart
Atrioventricular (AV) node
Atrioventricular bundle (Bundle of His)
Left and right bundle branches
Purkinje fibers
Modification by the ANS and hormones
Cardiac Physiology
Electrocardiogram - ECG
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P wave - atrial depolarization
QRS complex - ventricular depolarization
T wave - ventricular repolarization
Atrial repolarization is masked by the
larger QRS complex
Arrhythmias
Abnormal Heart Rhythms
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Heart block - blockage in the AV node
Tachycardia - >100 beats per minute
Bradycardia - <60 beats per minute
Fibrillation - uncoordinated quivering
Flutter - rapid contractions
PVC - premature ventricular contraction
PAC - preatrial contraction
Terms
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Myocardial infarction (MI) - heart attack
Infarction - tissue death due to loss of
blood supply
Ischemia - decreased blood flow
causing hypoxia
Angina pectoralis - chest pain related to
coronary problems
Cardiac Cycle
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Cardiac cycle consists of one complete
cycle of contraction and relaxation
Contraction phase - systole
Relaxation phase - diastole
Complete cycle - 0.8 seconds
Phases : relaxation period, ventricular
filling, ventricular systole
Normal heart rate - 75 beats/minute
Cardiac Output
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CO = Stroke volume x Heart rate
 Amount of blood passing through a
ventricle in 1 minute
SV = Amount of blood that is pumped by a
ventricle per beat (approx. 70 ml)
HR = number of beats per minute
Examples
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Rest - CO = 70ml/beat x 75 beats/min
= 5250ml/minute
=5.25 liters/minute
Exercise CO = 140ml/beat x 150 beats/min
= 21,000ml/minute
= 21 liters /minute
Factors influencing stroke
volume
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“Frank - Starling law of the heart”
Critical factor = stretch of cardiac muscle
Preload - how much blood enters a ventricle
during diastole
Contractility - forcefulness of a contraction
Afterload - pressure needed before ventricle
ejection occurs
Regulation of Heart Rate
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Cardiovascular Center
Medulla
Sympathetic nervous
system
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 Cardiac accelerator
nerves
Parasympathetic nervous
system
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 Vagus nerve
Baroreceptors monitor pressure
 aortic arch
 carotid arteries
Chemoreceptors monitor chemicals
 aortic/carotid
bodies
Hormones, age,
fitness,gender