Cardiovascular System
1
Size of Heart
Average Size of Heart
• 14 cm long
• 9 cm wide
2
Location of Heart
• posterior to sternum
• medial to lungs
• anterior to vertebral column
• base lies beneath 2nd rib
• apex at 5th intercostal space
• lies upon diaphragm
3
Coverings of Heart
4
Wall of the Heart
5
Wall of the Heart
6
Heart Chambers
Right Atrium
• receives blood from
• inferior vena cava
• superior vena cava
• coronary sinus
Right Ventricle
• receives blood from
right atrium
Left Atrium
• receives blood from
pulmonary veins
Left Ventricle
• receives blood from
left atrium
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Heart Valves
8
Coronal Sections of Heart
9
Heart Valves
Tricuspid Valve
Pulmonary and Aortic Valve
10
Skeleton of Heart
• fibrous rings to which the heart valves are attached
11
Path of Blood
Through the Heart
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Path of Blood
Through the Heart
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Blood Supply to Heart
14
Blood Supply to Heart
15
Angiogram of Coronary
Arteries
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Heart Actions
Atrial Systole/Ventricular Diastole
Atrial Diastole/Ventricular Systole
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Cardiac Cycle
Atrial Systole/Ventricular Diastole
• blood flows passively into ventricles
• remaining 30% of blood pushed into ventricles
• A-V valves open/semilunar valves close
• ventricles relaxed
• ventricular pressure increases
18
Cardiac Cycle
Ventricular Systole/Atrial diastole
• A-V valves close
• chordae tendinae prevent cusps of valves from
bulging too far into atria
• atria relaxed
• blood flows into atria
• ventricular pressure increases and opens semilunar
valves
• blood flows into pulmonary trunk and aorta
19
Heart Sounds
Lubb
• first heart sound
• occurs during ventricular systole
• A-V valves closing
Dupp
• second heart sound
• occurs during ventricular diastole
• pulmonary and aortic semilunar valves closing
Murmur – abnormal heart sound
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Heart Sounds
21
Cardiac Muscle Fibers
Cardiac muscle fibers form a functional
syncytium
• group of cells that function as a unit
• atrial syncytium
• ventricular syncytium
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Cardiac Conduction System
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Cardiac Conduction System
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Muscle Fibers in
Ventricular Walls
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Electrocardiogram
• recording of electrical changes that occur in the myocardium
• used to assess heart’s ability to conduct impulses
P wave – atrial depolarization
QRS wave – ventricular depolarization
T wave – ventricular repolarization
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Electrocardiogram
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Electrocardiogram
A prolonged QRS complex may result from damage to the A-V
bundle fibers
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Cardiac Cycle
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Regulation of Cardiac Cycle
Autonomic nerve impulses alter the
activities of the S-A and A-V nodes
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Regulation of Cardiac Cycle
Additional Factors that Influence HR
• physical exercise
• body temperature
• concentration of various ions
• potassium
• calcium
• parasympathetic impulses decrease heart action
• sympathetic impulses increase heart action
• cardiac center regulates autonomic impulses to the heart
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Blood Vessels
• arteries
• carry blood away from ventricles of heart
• arterioles
• receive blood from arteries
• carry blood to capillaries
• capillaries
• sites of exchange of substances between
blood and body cells
• venules
• receive blood from capillaries
• veins
• carry blood toward ventricle of heart
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Arteries and Arterioles
Artery
• thick strong wall
• endothelial lining
• middle layer of smooth
muscle and elastic tissue
• outer layer of
connective tissue
• carries blood under
relatively high pressure
Arterioles
• thinner wall than
artery
• endothelial lining
• some smooth muscle
tissue
• small amount of
connective tissue
• helps control blood
flow into a capillary
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Walls of Artery and Vein
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Arteriole
• smallest arterioles only have a few smooth muscle fibers
• capillaries lack muscle fibers
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Metarteriole
connects arteriole directly to venule
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Capillaries
• smallest diameter blood vessels
• extensions of inner lining of arterioles
• walls are endothelium only
• semipermeable
• sinusoids – leaky capillaries
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Capillary Network
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Regulation of Capillary
Blood Flow
Precapillary
sphincters
• may close a
capillary
• respond to
needs of the cells
• low oxygen and
nutrients cause
sphincter to
relax
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Exchange in the Capillaries
• water and other substances leave capillaries because of net outward pressure
at the capillaries’ arteriolar ends
• water enters capillaries’ venular ends because of a net inward pressure
• substances move in and out along the length of the capillaries according to
their respective concentration gradients
40
Venules and Veins
Venule
• thinner wall than arteriole
• less smooth muscle and elastic tissue than arteriole
Vein
• thinner wall than artery
• three layers to wall but middle layer is poorly developed
• some have flaplike valves
• carries blood under relatively low pressure
• serves as blood reservoir
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Venous Valves
42
Characteristics of Blood Vessels
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Blood Volumes in Vessels
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Arterial Blood Pressure
Blood Pressure – force the blood exerts against the
inner walls of the blood vessels
Arterial Blood Pressure
• rises when ventricles contract
• falls when ventricles relax
• systolic pressure – maximum pressure
• diastolic pressure – minimum pressure
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Pulse
• alternate expanding and recoiling of the arterial wall
that can be felt
46
Factors That Influence
Arterial Blood Pressure
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Control of Blood Pressure
Controlling cardiac output and peripheral resistance
regulates blood pressure
48
Control of Blood Pressure
If blood pressure rises, baroreceptors initiate the
cardioinhibitory reflex, which lowers the blood pressure
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Control of Blood Pressure
Dilating arterioles helps regulate blood pressure
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Venous Blood Flow
• not a direct result of heart
action
• dependent on
• skeletal muscle
contraction
• breathing
• venoconstriction
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Central Venous Pressure
• pressure in the right atrium
• factors that influence it alter flow of blood into
the right atrium
• affects pressure within the peripheral veins
• weakly beating heart increases central venous
pressure
• increase in central venous pressure causes blood
to back up into peripheral vein
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Pulmonary Circuit
• consists of vessels that carry blood from the heart to the lungs
and back to the heart
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Blood Flow Through Alveoli
• cells of alveolar wall are tightly joined together
• the high osmotic pressure of the interstitial fluid draws
water out of them
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Systemic Circuit
• composed of vessels that lead from the heart to
all body parts (except the lungs) and back to the
heart
• includes the aorta and its branches
• includes the system of veins that return blood to
the right atrium
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Major Vessels of Arterial
System
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Major Blood Vessels of the
Heart
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Principal Branches of the
Aorta
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Abdominal Aorta and Its
Major Branches
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Arteries to Neck, Head, and
Brain
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Cerebral Arterial Circle
• Circle of Willis
• formed by anterior and posterior cerebral arteries, which
join the internal carotid arteries
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Arteries to Shoulder
and Upper Limb
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Arteries to Thoracic Wall
63
Arteries to Pelvic Region
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Arteries to the Lower Limb
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Major Vessels of the Venous
System
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Major Veins of the Brain, Head
and Neck
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Veins from the Upper Limb
and Shoulder
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Veins That Drain the Thoracic
Wall
69
Veins That Drain the
Abdominal Viscera
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Veins from the Abdominal Viscera:
Hepatic Portal Vein
Hepatic portal vein drains one set of capillaries
and leads to another set
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Veins of the Lower Limb and
Pelvis
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Life-Span Changes
• cholesterol deposition in blood vessels
• heart enlargement
• death of cardiac muscle cells
• increase in fibrous connective tissue of the heart
• increase in adipose tissue of the heart
• increase in blood pressure
• decrease in resting heart rate
73
Clinical Application
Arrhythmias
Ventricular fibrillation
• rapid, uncoordinated
depolarization of ventricles
Tachycardia
• rapid heartbeat
Atrial flutter
• rapid rate of atrial
depolarization
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