Transcript Chapter 13 The Heart and Heart Disease

Chapter 13
The Heart
Location, Size, and
Position of the Heart
• In mediastinum
• 2/3 to the left of the body midline
• Apex = point
– Most inferior portion
• Shape and size of a closed fist
• Septum divides right and left sides
(internally)
Pericardium
• Two-layered fibrous sac
– Inner layer = visceral pericardium or epicardium
– Pericardial Cavity filled with pericardial fluid
– Outer layer = parietal pericardium
Three layers of the Heart Wall
– Epicardium
• Outer layer
• Connective tissue
– Myocardium
• Middle layer
• Thick
• Muscle
– Endocardium
• Inner layer (lining)
• Very thin, smooth
Summary of layers
• Outside (external) to Inside (internal)
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Parietal Pericardium
Pericardial cavity (filled with fluid)
Visceral Pericardium/Epicardium
Myocardium
Endocardium
Coronary Circulation
• Blood for the myocardium of the heart,
flows through the right and left coronary
arteries
• Blockage of blood flow through the
coronary arteries can cause myocardial
infarction (heart attack)
Anatomy of the Heart
• Heart chambers
– Two upper chambers are
• Right and left atria (atrium)
• Small chambers
• Receive blood
– Two lower chambers called ventricles
• Right and left ventricles
• Larger chambers
• Pump blood out of heart
Vessels
• Pulmonary Arteries
– Carry blood from R ventricle to lungs
– R pulmonary artery to R lung
– L pulmonary artery to L lung
• Pulmonary Veins
– Carry blood from lungs to L atria
– R pulmonary veins from R lung
– L pulmonary veins from L lung
Vessels cont.
• Vena Cava
– Inferior and superior
– Empties blood into heart from body
Valves
– Cuspid valves
• Tricuspid: between right atrium and ventricle
• Bicuspid (mitral): between left atrium and ventricle
• Open and close from chordae tendineae
– Semilunar valves
• Pulmonary Semilunar: base of pulmonary arteries
• Aortic Semilunar: base of aorta
• Open and close from pressure within heart
The heart acts as two pumps
Right atrium and ventricle
pump deoxygenate blood to the lungs
Left atrium and ventricle
pump oxygenated blood to the body
Blood Flow Pathway
• Superior and Inferior
Vena Cava
• Right atrium
• Tricuspid valve
• Right ventricle
• Pulmonary Semilunar
Valve
• Pulmonary Arteries
• Lungs
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Pulmonary Veins
Left atrium
Bicuspid valve
Left Ventricle
Aortic Semilunar
Valve
• Aorta
• Body
Conduction System of the Heart
– SA (sinoatrial) node
• The pacemaker
• In wall of right atrium near superior vena cava
– AV (atrioventricular) node
• In the floor of right atrium near septum
– AV bundle (bundle of His)
• Located in the septum of the ventricle
– Purkinje fibers—
• Located in the walls of the ventricles
• Cause contraction of myocardium
Conduction System of the Heart
• Electrocardiography
– Measures the electrical impulses that result in
contraction of the heart
– Impulses transformed into visible tracings by a
machine called an electrocardiograph
– The visible tracing of these electrical signals is
called an electrocardiogram or ECG
Conduction System of the Heart
– The normal ECG has three deflections or
waves called the P wave, the QRS complex,
and the T wave
• P wave—associated with depolarization of the atria
• QRS complex—associated with depolarization of the
ventricles
• T wave—associated with repolarization of the
ventricles
Some other odds and ends…
Heart Actions
• Contraction is called systole
• Relaxation is called diastole
Heart Sounds
• Two distinct heart sounds in every heartbeat or
cycle—“lubb-dupp”
• First (lubb) sound is caused by the vibration and
closure of AV valves during contraction of the
ventricles
• Second (dupp) sound is caused by the closure
of the semilunar valves during relaxation of the
ventricles
Cardiac Cycle
• Heart beat is regular and rhythmic—each
complete beat called a cardiac cycle—
average is about 72 beats per minute
• Each cycle, about 0.8 seconds long,
subdivided into systole (contraction phase)
and diastole (relaxation phase)
Cardiac Cycle
• Stroke volume is the volume of blood
ejected from one ventricle with each beat
• Cardiac output is amount of blood that one
ventricle can pump each minute—average
is about 5 L per minute at rest