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The Cardiovascular System


The Cardiovascular System Chapter 11 – PowerPoint PPT presentation

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Title: The Cardiovascular System

The Cardiovascular System
  • Chapter 11

The Cardiovascular System
  • Cardiovascular system is a closed system
  • Consists of
  • Heart The heart pumps blood
  • Blood vessels Blood vessels allow blood to
    circulate to all parts of the body
  • Function
  • To deliver oxygen and nutrients and to remove
    carbon dioxide and other waste products

  • Heart is transport system pump for the blood
  • Heart is two pumps in one
  • Pulmonary Circulation
  • R side of heart receives blood
  • from body, pumps blood to lungs
  • and returns to L heart
  • Systemic Circulation
  • L side of heart pumps blood to
  • tissues of the body return to
  • R heart
  • Heart of healthy person pumps
  • approx. 7200 L of blood each day
  • at the rate of 5L/min.

Anatomy of the Heart
  • Location, size and shape of Heart
  • Size size of a closed fist
  • Shape
  • Apex Blunt rounded cone
  • Base larger flat part
  • Location
  • Located in thoracic cavity in left of mediastinum
    (midline) between the two lungs
  • Superior surface of diaphragm
  • Important clinically when using a stethoscope,
    performing an ECG, or performing CPR

Anatomy of the Heart
  • Heart is enclosed by a double-walled sac called
  • Composed of
  • A superficial fibrous pericardium
  • A deep two-layer serous pericardium
  • Parietal pericardium lines the internal surface
    of the fibrous pericardium
  • The visceral pericardium or epicardium lines the
    surface of the heart
  • separated by fluid-filled pericardial cavity
  • Helps in reducing friction as heart moves within
    the pericardial sac

Anatomy of the Heart
  • Heart Wall composed of 3 layers of tissues
  • Epicardium visceral layer of the serous
    pericardium, lines the surface of the heart
  • Myocardium Middle layer, cardiac muscle layer
    forming the bulk of the heart, responsible for
    heart contraction
  • Endocardium Lines inner surface of heart

Heart Chambers and Vessels
  • Heart consists of 4 chambers
  • Two atria, two ventricle
  • Atria Thin walled, forms the superior
  • part of heart
  • Ventricle Thick-walled, forms the
  • inferior part of heart
  • Large veins carry blood to the heart
  • Superior and inferior venae cavae
  • carry blood from body to R atrium
  • 4 pulmonary veins carry blood from lungs to L.
  • Arteries conveying blood away from heart
  • Aorta carries blood from L. ventricle to the
  • Pulmonary trunk carries blood from R. ventricle
    to lungs

Heart Chambers and Valves
  • Atria
  • Right atrium three major openings to receive
    blood returning from the body (superior vena
    cava, inferior vena cava, coronary sinus)
  • Left atrium four openings that receive blood
    from 4 pulmonary veins from lungs
  • Two atria are separated from each other by
    Interatrial septum

Heart Chambers and Valves
  • Ventricles
  • Atrioventricular valves openings between atria
    and ventricles
  • Right ventricle opens to pulmonary trunk
  • Left ventricle opens to aorta
  • Interventricular septum between the two ventricle

Heart Valves
  • Heart valves ensure unidirectional blood flow
    through the heart
  • Atrioventricular (AV) valves lie between the
    atria and the ventricles
  • AV valves allow blood flow from atria to
  • But prevent backflow into the atria when
    ventricles contract
  • AV valve between L atrium L ventricle has 2
    cusps Bicuspid Valve
  • AV valve between R atrium R ventricle has 3
    cusps Tricuspid Valve

Heart Valves
  • Semilunar Valves
  • Aortic semilunar valve lies between the left
    ventricle and the aorta
  • Pulmonary semilunar valve lies between the right
    ventricle and pulmonary trunk
  • Semilunar valves prevent backflow of blood into
    the ventricles

Blood Flow Through the Heart
  • Superior and inferior vena cava dump blood into
    the right atrium
  • From right atrium, through the tricuspid valve,
    blood travels to the right ventricle
  • From the right ventricle, blood leaves the heart
    as it passes through the pulmonary semilunar
    valve into the pulmonary trunk
  • Pulmonary trunk splits into right and left
    pulmonary arteries that carry blood to the lungs

Blood Flow Through the Heart
  • Oxygen is picked up and carbon dioxide is dropped
    off by blood in the lungs
  • Oxygen-rich blood returns to the heart through
    the four pulmonary veins from lungs
  • Blood enters the left atrium and travels through
    the bicuspid valve into the left ventricle
  • From the left ventricle, blood leaves the heart
    via the aortic semilunar valve and aorta
  • From aorta, supply blood to all body parts

Blood Flow Through the Heart
Cardiac Circulation
  • Blood in the heart chambers does not nourish the
    heart muscles
  • Coronary arteries in heart supply blood to heart
  • Coronary arteries branch from the aorta to supply
    the heart muscle with oxygenated blood
  • Cardiac veins from heart drain blood into a
    large venous cavity called Coronary sinus
  • Coronary sinus then empties into the right atrium

Physiology of Heart
  • Heart muscle cells contract, without nerve
    impulses, in a regular, continuous way
  • Heart is autorhythmic
  • Initiate, conduct and impulse
  • Heart contains special tissue that produces
    sends electrical impulses to the heart muscle to

Physiology of Heart
  • The heart's conducting system consists of
  • Sinoatrial (SA) node
  • Atrioventricular (AV)node
  • Bundle of His
  • Bundle branches
  • Purkinje fibers

Physiology of Heart
  • Sinoatrial (SA) Node
  • Mass of autorhythmic cells
  • Electrical impulse that causes rhythmic
    contraction of heart muscles arises in the SA
  • Pacemaker of the heart
  • Located in R. atrium
  • Send impulse 70 to 80 times a minute

Physiology of Heart
  • AV Node
  • The electrical impulse from the SA node spreads
    over the right and left atria
  • causes atrial contraction
  • Then impulses are conducted to the
    atrioventicular (AV) node

Physiology of Heart
  • Bundle of His (AV bundle)
  • Then electrical impulse is relayed down to Bundle
    of HIS
  • Conducts impulse to right and left bundle
  • Bundle Branches
  • Right and left branches
  • Branch into purkinje fibers
  • Purkinje Fibers
  • Enter myocardium of ventricle walls
  • Carry impulse to ventricles
  • Ventricular contraction

Sinoatrial Node
AV Node
AV Bundle
Bundle Branches
Purkinje Fibers
Cardiac Cycle
  • Cardiac cycle Is the sequence of events in one
  • It is the repetitive pumping process that begins
    with onset of cardiac muscle contraction and ends
    with beginning of next contraction
  • Cardiac muscle contraction is responsible for
    pressure and blood movement. How?
  • Blood moves from high pressure to low pressure

Cardiac Cycle
  • The length of cardiac cycle is about 0.8 sec
  • Interval from end of one contraction to the
    following contraction
  • Consists of Two Phases
  • Systole phase
  • Diastole phase

  • Systole Phase
  • Contraction phase
  • Atrial Systole (0.1 sec.)
  • After passive filling with blood
  • Atrial pressure rises above ventricular pressure
  • And AV valves open
  • Blood is ejected from atria to ventricle
  • semilunar valves closed
  • Ventricles fill with blood

  • Ventricular Systole (0.3 sec.)
  • AV and semilunar valves closed until Ventricle
    pressure rises above aorta and pulmonary trunk
  • opens semilunar valves
  • Blood pushed into pulmonary trunk and Aorta
  • 120 mm Hg pressure
  • Atria in diastole

  • Diastole Phase
  • Relaxation phase
  • Ventricular Diastole
  • Follows ventricular systole
  • AV valves reopen and filling begins
  • 80 mm Hg pressure

Electrocardiogram ECG
  • When impulse pass through the heart, electric
    currents are generated
  • Electric current that can be measured at the
    surface of the
  • body - ECG
  • P wave Atrial depolarization
  • QRS complex Ventricular
  • depolarization
  • T wave Ventricular
  • repolarization

Heart Contractions
  • Tachycardiarapid heart rate over 100 beats per
  • Bradycardiaslow heart rate less than 60 beats
    per minutes

Heart Sounds
  • First heart sound or lubb
  • Atrioventricular valves vibrations as valves
    close at beginning of ventricular systole
  • Second heart sound or dupp
  • Results from closure of aortic and pulmonary
    semilunar valves at beginning of ventricular
    diastole, lasts longer

Cardiac Output
  • Cardiac output (CO)
  • Amount of blood pumped by heart in one minute
  • Stroke volume (SV)
  • Volume of blood pumped by each heartbeat
  • Usually remains relatively constant
  • About 70 mL of blood is pumped out of the left
    ventricle with each heartbeat
  • Heart rate (HR)
  • Typically 75 beats per minute

Cardiac Output
  • CO HR ? SV
  • CO HR (75 beats/min) ? SV (70 mL/beat)
  • CO 5250 mL/min
  • Starlings law of the heart the more the cardiac
    muscle is stretched, the stronger the contraction
  • Important factor for stretching the heart muscle
    is venous return
  • The greater the volume of blood returned to the
    heart by the veins, the greater the volume of
    blood the heart will pump

Regulation of the Heart
  • To maintain homeostasis, amount of blood pumped
    by heart must vary
  • Eg. Cardiac output increases more during
    exercise than resting
  • Intrinsic regulation Results from normal
    functional characteristics of heart, not depend
    on neural or hormonal regulation

Regulation of the Heart
  • Extrinsic regulation Involves neural and
    hormonal control
  • Neural Control
  • Parasympathetic stimulation
  • Supplied by vagus nerve, acetylcholine is
  • decreases heart rate, maintain
  • heart beat average of 70 beats/min.
  • Sympathetic stimulation
  • Supplied by cardiac nerves
  • Increases heart rate and force of contraction.
  • Epinephrine and norepinephrine released.
  • Increased heart beat causes increased cardiac

Regulation of the Heart
  • Hormonal Control
  • Epinephrine and norepinephrine from the adrenal
  • Increases rate and force of heart contraction
  • Occurs in response to increased physical
    activity, emotional excitement, stress

Blood Vessels The Vascular System
  • Transport blood to the tissues and back
  • Carry blood away from the heart
  • Arteries
  • Arterioles
  • Exchanges between tissues and blood
  • Capillary beds
  • Return blood toward the heart
  • Venules
  • Veins

Generalized Structure of Blood Vessels
  • Arteries and veins are composed of three tunics
    (layers) tunica intima, tunica media, and
    tunica externa
  • Lumen central blood-containing space surrounded
    by tunics
  • Capillaries are composed of endothelium

Blood Vessels Microscopic Anatomy
  • Three layers (tunics)
  • Tunic intima
  • Endothelium
  • Basement membrane
  • Tunic media
  • Smooth muscle
  • Blood flow is regulated by smooth muscle of
    Tunica Media
  • Vasoconstriction smooth muscles contract,
    decrease in blood flow
  • Vasodilation smooth muscles relax, increase in
    blood flow
  • Controlled by sympathetic nervous system
  • Tunic externa
  • Mostly fibrous connective tissue
  • Thickness of each layer varies with type and
    diameter of blood vessel

Differences Between Blood Vessels
  • Walls of arteries are the thicker than veins
  • Lumens of veins are larger than arteries
  • Because BP is low in veins and work against
  • Larger veins have valves to prevent backflow
  • More valves in veins of lower extremities than
    in veins of upper extremities
  • Walls of capillaries are only one cell layer
    thick to allow for exchanges between blood and

Movement of Blood Through Vessels
  • Most arterial blood is pumped by the heart
  • Veins use the milking action of muscles to help
    move blood

Capillary Beds
  • Capillary beds consist of two types of vessels
  • Vascular shunt vessel directly connecting an
    arteriole to a venule
  • True capillaries exchange vessels
  • Oxygen and nutrients cross to cells
  • Carbon dioxide and metabolic waste products cross
    into blood

Circulatory Pathways
  • The vascular system has two distinct circulations
  • Pulmonary circulation short loop that runs from
    the heart to the lungs and back to the heart
  • Systemic circulation routes blood through a
    long loop to all parts of the body and returns to
    the heart

Pulmonary Circulation
  • Heart pumps blood from right ventricle into
    pulmonary trunk
  • Pulmonary trunk divides into left and right
    pulmonary arteries, Transport blood to each lung
  • Two pulmonary veins exit each lung and enter left

Systemic Circulation Arteries
  • Oxygenated blood enter the heart from pulmonary
    veins through L. atrium
  • From L. atrium to L. ventricle
  • From L. ventricle to aorta
  • From aorta blood flows to all body parts

Systemic Circulation Arteries
  • Aorta
  • All arteries are derived from aorta
  • Aorta is divided into 3 parts
  • Ascending aorta
  • Aortic arch
  • Descending aorta
  • Ascending aorta Passes superiorly to heart, has
    2 branches
  • right and left coronary arteries, supply blood to
    cardiac muscles
  • Aortic arch arching posteriorly and to the left
    and has 3 branches, carry blood to head and neck
  • Brachiocephalic artery
  • Left common carotid
  • Left subclavian artery

Systemic Circulation Arteies
  • Aorta
  • Descending aorta Longest part
  • Consists of
  • Thoracic aorta portion in thorax
  • Abdominal aorta inferior to diaphragm branches
    supply blood to abdominal wall and organs
  • Ends as two common iliac arteries supply blood
    to pelvis lower limbs
  • Coronary Arteries
  • - Only branches of ascending arteries, supply
    blood to heart

Major veins of the Systemic Circulation
  • Return blood from body to right atrium
  • Major veins
  • Coronary sinus returning blood from heart walls
  • Superior vena cava Returning blood from head,
    neck, thorax, upper limbs
  • Inferior vena cava Returning blood from abdomen,
    pelvis, lower limbs
  • Types of veins
  • Superficial, deep, sinuses (cranium heart)

Special Circulations
  • Arterial Supply of Brain
  • Supply of blood to brain is crucial
  • Lack of O2 kills the brain cells that cannot be
  • The main arteries that supply blood to brain
  • Internal carotid artery
  • Vertebral artery
  • Internal carotid arteries divide into
  • Anterior and middle cerebral arteries
  • These arteries supply most of the cerebrum
  • Vertebral arteries join once within the skull to
    form the basilar artery
  • Basilar artery serves the brain stem and

Special Circulations
  • Arterial Supply of the Brain
  • Basilar artery divides to form Posterior cerebral
  • These arteries supply the posterior cerebrum
  • Anterior and posterior blood supplies are united
    by small communicating arterial branches
  • Resultcomplete circle of connecting blood
    vessels called cerebral arterial circle or circle
    of Willis around the pituitary gland

Hepatic Portal System
  • Nutrients and other substances absorbed by
    stomach and intestine are transported to liver by
    hepatic portal system
  • Hepatic portal system carries blood through
    veins from capillaries of stomach, intestine,
    spleen to liver
  • Largest vein of the system
  • From liver Hepatic veins join the Inferior vena

  • Pulse
  • Pressure wave of blood
  • Monitored at pressure points in arteries where
    pulse is easily palpated
  • Pulse averages 7076 beats per minute at rest

  • Pressure exerted on vessel walls
  • Blood pressure measured in mm Hg
  • Measured with sphygmomanometer
  • Pressure in cuff compresses artery until no pulse
  • Systolic pressure taken at first pulse as
    pressure in cuff released (ave. 120) pressure
    while heart ventricles contracting, 1st Korotkoff
  • Diastolic pressure taken when cuff released to
    point where sound no longer audible (ave. 80)
    pressure when ventricles not contracting
  • Pulse pressure systolic - diastolic (measure
    of stress exerted on small arteries)

Blood Pressure Effects of Factors
  • Blood Pressure varies directly with the
  • Cardiac Output
  • Stroke volume X heart rate
  • Normal is 5.5 liters/min.
  • Peripheral Resistance
  • Opposition to blood flow
  • ? with blood viscosity
  • ? with length of vessel
  • ? with ? in vessel diameter (has the greatest
    influence on B.P.)

  • Blood Pressure varies directly with the
  • Blood Volume
  • Mainly regulated by kidneys
  • ? in blood volume ? in B.P.
  • ? in blood vol. ? decrease in B.P.

  • Neural Factors
  • Sympathetic nerve fibers cause
  • Vasoconstriction of blood vessels
  • ? diameter, ? resistance ? ? B.P.

  • Renal Factors
  • Renin (Enzyme)
  • Renin enzyme released from kidneys in response to
    low B.P.
  • Stimulates angiotensin II, vasoconstrictor
  • Which stimulates hormone aldosterone
  • Which enhances sodium and water reabsorption
  • ? blood volume and B.P.

  • Temperature
  • Heat has a vasodilating effect
  • Cold has a vasoconstricting effect
  • Chemicals
  • Various substances can cause increase or decrease
    in B.P.
  • Diet

Variations in Blood Pressure
  • Normal human 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)
  • Can be dangerous if it is chronic