Download Cardiovascular System notes

Chapter 15
Cardiovascular System
1
Size of Heart
Average Size of Heart
•  14 cm long
•  9 cm wide
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Location of Heart
• Hollow, cone-shaped
muscular pump
• posterior to sternum
•  medial to lungs
•  anterior to vertebral
column
•  base lies beneath 2nd rib
•  apex at 5th intercostal space
•  lies upon diaphragm
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1
Coverings of Heart
• Pericardium covering that encloses
the heart and the
proximal ends of the
large blood vessels to
which it attaches
• Fibrous pericardium
• Visceral pericardium
• Parietal pericardium
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Wall of the Heart
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Wall of the Heart
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2
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
Interatrial and interventricular steptum
• Separates the heart into left and right halves
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Heart Valves
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Heart Valves
Tricuspid Valve
Pulmonary and Aortic Valve
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3
Skeleton of Heart
•  fibrous rings to which the heart valves are attached
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Path of Blood
Through the Heart
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Blood Supply to Heart
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4
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
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5
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
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Heart Sounds
Lubb
•  first heart sound
•  occurs during ventricular systole
•  A-V valves closing
Dubb
•  second heart sound
•  occurs during ventricular diastole
•  pulmonary and aortic semilunar valves closing
Murmur – abnormal heart sound
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Heart Sounds
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6
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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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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Cardiac Cycle
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8
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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10
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
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11
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
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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
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Factors That Influence
Arterial 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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Pulmonary Circuit
•  consists of vessels that carry blood from the heart to the lungs
and back to the heart
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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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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
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Clinical Application
Arrhythmias
Ventricular fibrillation
•  rapid, uncoordinated
depolarization of ventricles
Tachycardia
•  rapid heartbeat
Atrial flutter
•  rapid rate of atrial
depolarization
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Clinical Application
Atherosclerosis
• Caused by build of plaque on the walls of the arteries
• Factors that lead to plaque build up
• Lack of exercise
• Poor diet (high in saturated fats and cholesterol)
• Smoking
• Stress
• Genetics
Blood Clots
• Thrombus-blood clot
• Embolus
• Stroke
• Myocardial infarction
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