Chapter 11 The Cardiovascular System

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Chapter 11The Cardiovascular System
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The 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 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 Heart
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The 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 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 Anatomy
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The 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 Circulation
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The 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 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 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 Valves
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Coronary 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 Surgery

• Website
• Coronary Bypass Surgery

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Balloon Angioplasty Coronary Angioplasty
Stenting
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Heart View
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The 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 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 Contractions
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Electrocardiograms (EKG/ECG)

• 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

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Electrocardiograms (EKG/ECG)
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Abnormal EKG
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Pathology of the Heart

• Abnormal ECG
• Heart Block
• Damage to AV node ? Ventricles are partially or
  totally released from the control of the SA node
  ? Result slower heart beat
• Other conditions can damage the SA node resulting
  in a slower heart rate
• Surgically 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 adults
• Tachycardia (If prolonged, can lead to
  fibrillation)
• 100 beats/min
• Bradycardia
• Less than 60 beats/min

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The 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 the Cardiac Cycle
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The 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 Rate

• Stroke volume usually remains relatively constant
• Starlings 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 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 Rate

• 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 Regulation
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Congestive Heart Failure (CHF)

• Decline in pumping efficiency of the heart ?
  Leading to inadequate circulation
• Progressive condition
• Causes Coronary atherosclerosis, high blood
  pressure and a history of multiple myocardial
  infarctions
• Left side fails
• Pulmonary congestion ? suffocation
• Right side fails
• Peripheral congestion and edema

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Blood Vessels The Vascular System

• Taking blood from the heart to the tissues and
  back
• Arteries
• Arterioles
• Capillaries
• Venules
• Veins

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Blood 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 System
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Differences Between Blood Vessel Types

• 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 Vessels

• 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 Beds

• Capillary beds consist of two types of vessels
• Vascular shunt directly connects an arteriole
  to a venule

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Capillary 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 Beds
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Vital Signs

• Arterial pulse
• Blood pressure
• Respiratory Rate
• Body Temperature

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Pulse

• Pulse pressure wave of blood
• Monitored at pressure points where pulse is
  easily palpated

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Blood 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 Pressure
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Blood 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 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 Pressure

• Human normal range is variable
• Normal
• 140110 mm Hg systolic
• 8075 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