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The Cardiovascular System:
The Anatomy of the Heart
13
Heart Anatomy
 Size: Approximately the size of your fist
 Location / Orientation
 Lies upon the superior surface of diaphragm
 Left of the midline / Apex pointed towards left hip
 Mediastinum
Heart Anatomy
Membranes of the Heart: Anatomy

Pericardium – a double-walled sac around the
heart composed of:
1. A superficial fibrous pericardium
2. A deep two-layer serous pericardium
a. The parietal layer lines the internal surface of
the fibrous pericardium
b. The visceral layer or epicardium lines the
surface of the heart

They are separated by the fluid-filled
pericardial cavity
Pericardial Layers of the Heart
Coverings of the Heart: Physiology
 The Function of the Pericardium:
 Protects and anchors the heart
 Prevents overfilling of the heart with blood
 Allows for the heart to work in a relatively frictionfree environment
Heart Wall
 Myocardium – cardiac muscle layer forming the
bulk of the heart wall
 Fibrous skeleton of the heart – crisscrossing,
interlacing layer of reticular connective tissue
 Endocardium – simple squamus epithelial inner
lining of the heart chambers
External Heart: Major Vessels of the Heart

Veins returning blood to the atria heart include:
1. Into the left atrium???
2. Into the right atrium???

Arteries carrying blood away from the ventricles of the
heart include:
1. Exiting the left ventricle (to Body)???
2. Exiting the right ventricle (to Lungs)???
External Heart: Anterior View
External Heart: Posterior View
Myocardial Thickness and Function
Thickness of myocardium varies according to the function of the
chamber
Atria are thin walled, deliver blood to adjacent ventricles
Ventricle walls are much thicker and stronger
 right ventricle supplies blood to the lungs
 left ventricle wall is the thickest to supply systemic circulation
Pathway of Blood Through the Heart and
Lungs
Right atrium  _______  Right ventricle
Pulmonary SL valve  _______ 
Pulmonary arteries Lungs  _______ 
_______  Bicuspid valve  Left ventricle 
_______  Aorta  Body  _______  Back to
the Right Atrium
Pathway of Blood Through the Heart and
Lungs
Fetal Structure of the Heart
 Fetal heart structures that bypass pulmonary
circulation
 Connects the two atria???
 Connects pulmonary trunk and the aorta???
Heart Valves: Atrioventricular
 Heart valves ensure unidirectional blood flow
through the heart
 Atrioventricular (AV) valves lie between the atria
and the ventricles (Bicuspid and Tricuspid Valve)
 AV valves prevent backflow into the atria when
ventricles contract
 Chordae tendineae anchor AV valves to papillary
muscles of the ventricles
Atrioventricular Valve Function
Heart Valves: Semilunar
 Semilunar valves prevent backflow of blood into the
ventricles
 Aortic semilunar valve lies between the left
ventricle and the aorta
 Pulmonary semilunar valve lies between the right
ventricle and pulmonary trunk
Semilunar Valve Function
Mitral Valve Prolapse
The Cardiovascular System:
The Physiology of the Heart
Chapter 13, Cardiovascular System
13
Heart Physiology: Sequence of Excitation
Intrinsic Conducting System
 Series of structures in the heart that generates and
relays the nerve impulse that triggers a heartbeat.
1. Sinoatrial (SA) node generates impulses about 75
times/minute (every .8 of a second)
2. Atrioventricular (AV) node delays the impulse
approximately 0.1 second
Heart Physiology: Sequence of Excitation
3. Impulse passes from atria to ventricles via the
atrioventricular bundle (bundle of His)
4. AV bundle splits into two pathways in the
interventricular septum, these Bundle branches
carry the impulse toward the apex of the heart
5. Purkinje fibers carry the impulse from the heart
apex up the outer ventricular walls
Heart Physiology: Sequence of Excitation
Heart Excitation Related to ECG
Electrocardiography
 Electrical activity is recorded by electrocardiogram
(ECG)
 P wave corresponds to depolarization of SA node
 QRS complex corresponds to ventricular
depolarization
 T wave corresponds to ventricular repolarization
 Atrial repolarization record is masked by the larger
QRS complex
Electrocardiography
Extrinsic Conduction of the Heart
 Medulla Oblongata
contains centers
 Heart is stimulated
by the sympathetic
cardioacceleratory
center
 Heart is inhibited by
the parasympathetic
cardioinhibitory
center
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Cardiac Cycle
 Cardiac cycle refers to all events associated with
blood flow through the heart
 Systole – contraction phase of heart muscle
 Diastole – relaxation phase of heart muscle
Phases of the Cardiac Cycle
 Ventricular filling – mid-to-late diastole
 Heart is completely at rest
 Heart blood pressure is low as blood enters atria
and passively flows into ventricles
 AV valves are open, SL valves are closed  then
atrial systole occurs
Phases of the Cardiac Cycle
 Ventricular systole (contraction)
 Atria relax
 Rising ventricular pressure results in closing of AV
valves (LUBB)
 Isovolumetric contraction phase
 Ventricular ejection phase opens semilunar valves
Phases of the Cardiac Cycle
 Isovolumetric relaxation – early diastole
 Ventricles relax causing decrease in ventricular
pressure
 Backflow of blood in aorta and pulmonary trunk
closes semilunar valves (DUPP)
 Dicrotic notch – brief rise in aortic pressure caused
by backflow of blood rebounding off semilunar
valves
Phases of the Cardiac Cycle
Ventricular volume on
average is 120 to 130 mL
… Stroke volume on
average is 70 to 80 mL.
Cardiac output is the
amount of blood pumped
by each ventricle per
minute.
CO = SV x HR
Figure 18.20