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Chapter 11The
Cardiovascular System
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The Cardiovascular SystemThe Cardiovascular System Closed system of the heart and blood vessels
Heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
Blood is the transport vehicle Carries oxygen, nutrients, cell wastes, &
hormones, to and from the cells to maintain homeostasis
Function of the cardiovascular system To deliver oxygen and nutrients and to remove
carbon dioxide and other waste products
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The HeartThe Heart
Location Mediastinum
Middle cavity of the thorax, between the lungs
Pointed apex directed toward left hip
The great vessels of the heart emerge from the base which points toward the right shoulder and lies beneath the second rib
About the size of your fist Less than 1 lb.
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The HeartThe Heart
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The Heart: CoveringsThe Heart: Coverings
Pericardium – a double serous membrane Visceral pericardium
Hugs the external surface of the heart & is part of the heart wall
Parietal pericardium Outside layer
Serous fluid fills the space between the layers of pericardium
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The Heart: Heart WallThe Heart: Heart Wall Three layers
Epicardium Outside layer This layer is the visceral pericardium Connective tissue layer
Myocardium Middle layer Mostly cardiac muscle – Allows contraction
Endocardium Inner layer Endothelium
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External Heart AnatomyExternal Heart Anatomy
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The Heart: ChambersThe Heart: Chambers Right & left sides act as separate pumps Four chambers
Atria Receiving chambers
Right atrium Left atrium
Ventricles Discharging chambers
Right ventricle Left ventricle
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Blood CirculationBlood Circulation
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The Heart: Associated Great VesselsThe Heart: Associated Great Vessels
Aorta Leaves left ventricle
Pulmonary arteries Leave right ventricle
Vena cava Enters right atrium
Pulmonary veins (four) Enter left atrium
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The Heart: ValvesThe Heart: Valves Allows blood to flow in only one direction Four valves
Atrioventricular valves – between atria and ventricles Bicuspid (mitral) valve (left) Tricuspid valve (right)
Semilunar valves between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve
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The Heart: ValvesThe Heart: Valves
Valves open as blood is pumped through
Held in place by chordae tendineae (“heart strings”)
Close to prevent backflow
Aortic Valve Replacement Surgery
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Operation of Heart ValvesOperation of Heart Valves
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Coronary CirculationCoronary Circulation Blood in the heart chambers does not nourish
the myocardium
The heart has its own nourishing circulatory system
Right and left coronary arteries & their major branches
Are compressed when the ventricles are contracting and fill when the heart is relaxed
Cardiac veins
Drain the myocardium
Blood empties into the right atrium via the coronary sinus
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Angina & Myocardial Infarctionwebsite
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Bypass SurgeryWebsiteCoronary Bypass Surgery
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Balloon Angioplasty Coronary Angioplasty & Stenting
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Heart View
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The Heart: Conduction SystemThe Heart: Conduction System Autonomic Nervous system
Nerves = brakes & accelerators to decrease or increase heart rate Accelerators = Sympathetic Nervous system
Brakes = Parasympathetic Nervous system
Intrinsic conduction system- Nodal system
Heart muscle cells contract, without nerve impulses, in a regular, continuous fashion
Built into the heart tissue & sets its basic rhythm
Causes heart muscle depolarization in only 1 direction (From the atria to the ventricles)
Enforces a contraction rate of 75 beats/minute
Heart beats as a coordinated unit
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Intrinsic Conduction SystemIntrinsic Conduction System
Special type of tissue Sets the pace Sinoatrial (SA) node
Located within the right atrium Pacemaker Starts each heartbeat
Atrioventricular (AV) node Located at the junction of the right & left atria and
ventricles Atrioventricular bundle (Bundle of His) Bundle branches (right and left) Purkinje fibers
Spread within the muscle of the ventricle walls
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Heart ContractionsHeart Contractions
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• Three formations– P wave:
– Small & signals the depolarization of the atria immediately before they contract
– QRS complex:– Complicated shape– Depolarization of the ventricles
– T wave:– Repolarization of the ventricles
Electrocardiograms (EKG/ECG)
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Electrocardiograms (EKG/ECG)
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Abnormal EKG
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Pathology of the HeartAbnormal ECG:
Heart Block:Damage to AV node Ventricles are partially or totally released
from the control of the SA node Result = slower heart beatOther conditions can damage the SA node resulting in a
slower heart rateSurgically installation of an artificial pacemaker
Fibrillation Results from a lack of blood flow to the heart (ischemia)Rapid uncoordinated heartbeat that makes the heart useless as a
pump Major cause of death from heart attacks in adultsTachycardia (If prolonged, can lead to fibrillation)
+100 beats/minBradycardia
Less than 60 beats/min
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The Heart: Cardiac CycleThe Heart: Cardiac Cycle Cardiac cycle
Events of 1 complete heartbeat
Both atria & ventricles contract and then relax
Atria contract simultaneously and then relax ventricles then contract simultaneously and then relax
Systole
Contraction of the ventricles
Diastole
Relaxation of the ventricles
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Filling of Heart Chambers – Filling of Heart Chambers – the Cardiac Cyclethe Cardiac Cycle
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The Heart: Cardiac OutputThe Heart: Cardiac Output
Cardiac output (CO)
Amount of blood pumped out by each side of the heart (each ventricle) in one minute
CO = (heart rate [HR]) x (stroke volume [SV])
Varies with the demands of the body
Stroke volume (SV)
Volume of blood pumped out by a ventricle with each heartbeat
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The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate
Stroke volume usually remains relatively constant
Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction
Changing heart rate is the most common way to change cardiac output
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Regulation of Heart RateRegulation of Heart Rate
Increased heart rate Sympathetic nervous system stimulation
Activated in times of “Fight or Flight” Hormones
Epinephrine Thyroxine
Exercise Fever
Increases the metabolic rate of heart cells
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The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate
Decreased heart rate
Parasympathetic nervous system stimulation
Congestive heart failure
Heart is worn out and pumps weakly
Digoxin
Works to provide a slow, steady, but stronger beat
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Cardiac Output RegulationCardiac Output Regulation
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Congestive Heart Failure (CHF)Decline in pumping efficiency of the heart
Leading to inadequate circulationProgressive condition
Causes: Coronary atherosclerosis, high blood pressure and a history of multiple myocardial infarctions
Left side failsPulmonary congestion suffocation
Right side failsPeripheral congestion and edema
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Blood Vessels: Blood Vessels: The Vascular SystemThe Vascular System
Taking blood from the heart to the tissues and back Arteries
Arterioles
Capillaries
Venules
Veins
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Blood Vessels: AnatomyBlood Vessels: Anatomy Three layers (tunics)
Tunic intima Lines the lumen or interior of the vessels Endothelium slick surface, decreases friction as
blood flows through
Tunic media Middle coat Smooth muscle
Controlled by sympathetic nervous system Changes the diameter of the vessels
Constriction blood pressure increases Dilation blood pressure decreases
Tunic externa Mostly fibrous connective tissue Outermost tunic
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The Vascular SystemThe Vascular System
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Differences Between Blood Vessel Differences Between Blood Vessel TypesTypes
Walls of arteries are the thickest
Lumens of veins are larger than arteries
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
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Movement of Blood Through Movement of Blood Through VesselsVessels
Most arterial blood is pumped by the heart
Veins use the milking action of skeletal muscles to help move blood
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Varicose Veinswebsite
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Capillary BedsCapillary Beds
Capillary beds consist of two types of vessels
Vascular shunt – directly connects an arteriole to a venule
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Capillary BedsCapillary Beds
True capillaries – exchange vessels
Oxygen and nutrients cross to cells
Carbon dioxide and metabolic waste products cross into blood
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Diffusion at Capillary BedsDiffusion at Capillary Beds
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Vital SignsArterial pulseBlood pressureRespiratory RateBody Temperature
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PulsePulse
Pulse – pressure wave of blood
Monitored at “pressure points” where pulse is easily palpated
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Blood PressureBlood Pressure
Measurements by health professionals are made on the pressure in large arteries
Systolic – pressure at the peak of ventricular contraction
Diastolic – pressure when ventricles relax
Pressure in blood vessels decreases as the distance away from the heart increases
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Blood Pressure Changes
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Measuring Arterial Blood PressureMeasuring Arterial Blood Pressure
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Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors
Neural factors Autonomic nervous system adjustments
(sympathetic division)
Renal factors
Regulation by altering blood volume
Renin – hormonal control
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Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors
Temperature
Heat has a vasodilation effect
Cold has a vasoconstricting effect
Chemicals
Various substances can cause increases or decreases
Diet
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Variations in Blood PressureVariations in Blood Pressure Human normal range is variable
Normal 140–110 mm Hg systolic 80–75 mm Hg diastolic
Hypotension Low systolic (below 110 mm Hg) Often associated with illness
Hypertension High systolic (above 140 mm Hg) High diastolic (above 90) Can be dangerous if it is chronic
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Varicose Veinswebsite
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Blood Distribution