Download Chapter 2: Chemistry, Matter, and Life

Chapter 13:
The Heart
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Taylor: Memmler’s Structure and Function of the Human Body
Circulation and the Heart
Circulation
• Continuous one-way circuit of the blood vessels
• Propelled by heart
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Taylor: Memmler’s Structure and Function of the Human Body
Location of the Heart
• Between the lungs
• Left of the midline of the body
• In mediastinum
• Apex pointed toward left
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Taylor: Memmler’s Structure and Function of the Human Body
The heart in position in the thorax (anterior view).
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Taylor: Memmler’s Structure and Function of the Human Body
Structure of the Heart
Three tissue layers
• Endocardium lines heart’s interior
• Myocardium is thickest layer; the heart muscle
• Epicardium is thin outermost layer
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Taylor: Memmler’s Structure and Function of the Human Body
The Pericardium
The sac that encloses the heart
• Fibrous pericardium holds heart in place
• Serous membrane
– Parietal layer
– Pericardial cavity
– Visceral layer (epicardium)
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Taylor: Memmler’s Structure and Function of the Human Body
Special Features of the Myocardium
Cardiac muscles
• Are lightly striated (striped)
• Have single nucleus cells
• Are controlled involuntarily
• Have intercalated disks
– Modified plasma membranes
• Have branching muscle fibers
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Taylor: Memmler’s Structure and Function of the Human Body
Double pump
Divisions
of the
Heart
•
Right side pumps
blood
low in oxygen to the lungs
– Pulmonary circuit
• Left side pumps oxygenated blood to remainder of body
– Systemic circuit
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Taylor: Memmler’s Structure and Function of the Human Body
Four Chambers
• Right atrium
– Receives low-oxygen blood returning from body tissue
through superior vena cava and inferior vena cava
• Left atrium
– Receives high-oxygen blood from lungs
• Right ventricle
– Pumps blood from right atrium to lungs
• Left ventricle
– Pumps oxygenated blood to body
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Taylor: Memmler’s Structure and Function of the Human Body
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Taylor: Memmler’s Structure and Function of the Human Body
The
heart
and
great
vessels
.
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Taylor: Memmler’s Structure and Function of the Human Body
Four Valves
• Atrioventricular valves
– Entrance valves
– Right atrioventricular (AV) valve (tricuspid valve)
– Left atrioventricular (AV) valve (bicuspid valve)
• Attached by threads (chordae tendinae) to papillary
muscles
• Semilunar valves
– Exit valves
– Pulmonary valve
– Aortic valve
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Taylor: Memmler’s Structure and Function of the Human Body
Pathway
of blood
through
the
heart.
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Taylor: Memmler’s Structure and Function of the Human Body
Blood Supply to the Myocardium
Coronary circulation-own blood supply
• Right coronary artery
• Left coronary artery
• These arteries are the first to branch off from the aorta
• After passing through capillaries in the myocardium, blood
drains into a system of cardiac veins that bring blood back to
the R atrium
• Coronary sinus
– Dilated vein that opens into the R atrium near IVC
– Blood colllects here
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Taylor: Memmler’s Structure and Function of the Human Body
Blood vessels that supply the myocardium. Coronary
arteries and cardiac veins are shown. (A) Anterior
view. (B) Posterior view.
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Taylor: Memmler’s Structure and Function of the Human Body
Function of the Heart
Left and right sides of heart work together in cardiac cycle
(heartbeat)
• Systole (active phase, contraction)
• Diastole (resting phase)
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Taylor: Memmler’s Structure and Function of the Human Body
The cardiac cycle.
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Taylor: Memmler’s Structure and Function of the Human Body
Cardiac Output
Calculating cardiac output
• Cardiac output (CO)
• Stroke volume (SV)
• Heart rate (HR)
• CO = HR 3 SV
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Taylor: Memmler’s Structure and Function of the Human Body
The Heart’s Conduction System
Electrical energy stimulates heart muscle
• Nodes
– Sinoatrial (SA) node (pacemaker)
– Atrioventricular (AV) node
• Specialized fibers
– Atrioventricular bundle (bundle of His)
– Purkinje fibers (conduction myofibers)
• Intercalated disks
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Taylor: Memmler’s Structure and Function of the Human Body
The Conduction Pathway
Sinus rhythm
• Sinoatrial (SA) node
• Atria
• Atrioventricular (AV) node
• Internodal pathways
• Bundle of His
• Bundle branches and Purkinje fibers
• Ventricles
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Taylor: Memmler’s Structure and Function of the Human Body
Conduction
system of
the heart.
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Taylor: Memmler’s Structure and Function of the Human Body
Control of the Heart Rate
Influences that allow heart to meet changing needs rapidly
• Autonomic nervous system (ANS)
• Sympathetic nervous system
• Parasympathetic system
– Cranial nerve X
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Taylor: Memmler’s Structure and Function of the Human Body
Variations in Heart Rates
• Bradycardia
• Tachycardia
• Sinus arrhythmia
• Premature beat (extrasystole)
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Taylor: Memmler’s Structure and Function of the Human Body
Heart Sounds
• Lub
• Dup
• Murmurs
– Organic
– Functional
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Taylor: Memmler’s Structure and Function of the Human Body
The Heart in the Elderly
How the heart can age
• Heart shrinks
• Decreased contraction strength
• Valves become less flexible
• Murmur develops
• Cardiac output decreases
• Abnormal rhythms
• Heart block
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Taylor: Memmler’s Structure and Function of the Human Body
Maintaining Heart Health
• Risk factors that cannot be
modified
–
Age
–
Gender
–
Heredity
–
Body type
• Risk factors that can be modified
–
Smoking
–
Physical inactivity
–
Weight
–
Diet
–
Blood pressure
–
Diabetes
–
Gout
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Taylor: Memmler’s Structure and Function of the Human Body
Heart Studies
• Stethoscope
• Electrocardiograph (ECG or EKG)
– Electrodes
• Catheterization
– Fluoroscope
• Echocardiography (ultrasound cardiography)
– Oscilloscope
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Taylor: Memmler’s Structure and Function of the Human Body
Figure 13-12 Coronary angiography.
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Taylor: Memmler’s Structure and Function of the Human Body
Normal ECG
tracing.
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