The Cardiovascular
System
• Presented by : Jagruti Marathe

The Cardiovascular System
 A closed system of the heart and blood vessels
 The heart pumps blood
 Blood vessels allow blood to circulate to all parts of
the body
 The function of the cardiovascular system is to deliver
oxygen and nutrients and to remove carbon dioxide and
other waste products

The Heart and Homeostasis
The heart contributes to homeostasis by pumping blood
through blood vessels to the tissues of the body to deliver
oxygen and nutrients and remove wastes.

• Blood to reach body cells and exchange materials with them,
it must be pumped continuously by the heart through the
body’s blood vessels.
• The heart beats about 100,000 times every day, which adds
up to about 35 million beats in a year, and approximately 2.5
billion times in an average lifetime.
• The left side of the heart pumps blood through an estimated
100,000 km (60,000 mi) of blood vessels, which is
equivalent to traveling around the earth’s equator about three
times.
• The right side of the heart pumps blood through the lungs,
enabling blood to pick up oxygen and unload carbon
dioxide.

Location of the Heart
• The scientific study of the normal heart
and the diseases associated with it is
known as cardiology

Location of the Heart
 Location
Thorax between the lungs
Pointed apex directed toward left hip
 About the size of your fist
Less than 1 lb.

• The heart is relatively small, roughly the same size (but
not the same shape) as your closed fist.
• It is about 12 cm (5 in.) long, 9 cm (3.5 in.) wide at its
broadest point, and 6 cm (2.5 in.)
• thick, with an average mass of 250 g (8 oz) in adult
females and 300 g(10 oz) in adult males.
• The heart rests on the diaphragm, near the midline of the
thoracic cavity.
• Recall that the midline is an imaginary vertical line that
divides the body into unequal left and right sides.
• The heart lies in the mediastinum (mē′-dē-as-TĪ-num),
an anatomical region that extends from the sternum to
the vertebral column, from the first rib to the diaphragm,
and between the lungs.

• The pointed apex is formed by the tip of the left ventricle
(a lower chamber of the heart) and rests on the
diaphragm.
• It is directed anteriorly, inferiorly, and to the left .
• The base of the heart is opposite the apex and is its
posterior aspect.
• It is formed by the atria (upper chambers) of the heart,
mostly the left atrium .

The Heart
Position of the heart and associated structures in the mediastinum.
The positions of the heart and associated structures in the mediastinum are
indicated by dashed outlines. The heart is located in the mediastinum, with
two-thirds of its mass to the left of the midline.

• the heart has several distinct surfaces.
• The anterior surface is deep to the sternum and
ribs.
• The inferior surface is the part of the heart between
the apex and right surface and rests mostly on the
diaphragm (Figure ).
• The right surface faces the right lung and extends
from the inferior surface to the base.
• The left surface faces the left lung and extends from
the base to the apex.

The Heart: Coverings
 Pericardium – a double serous
membrane
Visceral pericardium
Next to heart
Parietal pericardium
Outside layer
 Serous fluid fills the space between the
layers of pericardium

The Heart: Heart Wall
 Three layers
Epicardium
 Outside layer
 This layer is the parietal pericardium
 Connective tissue layer
Myocardium
 Middle layer
 Mostly cardiac muscle
Endocardium
 Inner layer
 Endothelium

External Heart Anatomy
Figure 11.2a

The Heart: Chambers
 Right and left side act as separate pumps
 Four chambers
Atria
 Receiving chambers
 Right atrium
 Left atrium
Ventricles
 Discharging chambers
 Right ventricle
 Left ventricle

The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
Atrioventricular valves – between atria and
ventricles
 Bicuspid valve (left)
 Tricuspid valve (right)
Semilunar valves between ventricle and
artery
 Pulmonary semilunar valve
 Aortic semilunar valve

The Heart: Valves
 Valves open as blood is pumped
through
 Held in place by chordae tendineae
(“heart strings”)
 Close to prevent backflow

Operation of the Atrioventricular Valves
• Because they are located between an atrium and a ventricle,
the tricuspid and bicuspid valves are termed atrioventricular
(AV) valves.
• When an AV valve is open, the rounded ends of the cusps
project into the ventricle.
• When the ventricles are relaxed, the papillary muscles are
relaxed, the chordae tendineae are slack, and blood moves
from a higher pressure in the atria to a lower pressure in the
ventricles through open AV valves .
• When the ventricles contract, the pressure of the blood drives
the cusps upward until their edges meet and close the opening
. At the same time, the papillary muscles contract, which pulls
on and tightens the chordae tendineae

• This prevents the valve cusps from everting (opening into
the atria) in response to the high ventricular pressure.
• If the AV valves or chordae tendineae are damaged, blood
may regurgitate (flow back) into the atria when the
ventricles contract.

Operation of the Semilunar Valves
• The aortic and pulmonary valves are known as the semilunar
(SL) valves because they are made up of three crescent
moon–shaped cusps .
• Each cusp attaches to the arterial wall by its convex outer
margin.
• The SL valves allow ejection of blood from the heart into
arteries but prevent backflow of blood into the ventricles.
• The free borders of the cusps project into the lumen of the
artery.
• When the ventricles contract, pressure builds up within the
chambers.

• The semilunar valves open when pressure in the ventricles
exceeds the pressure in the arteries, permitting ejection of
blood from the ventricles into the pulmonary trunk and aorta
• As the ventricles relax, blood starts to flow back toward the
heart.
• This backflowing blood fills the valve cusps, which causes
the free edges of the semilunar valves to contact each other
tightly and close the opening between the ventricle and
artery .
• Surprisingly perhaps, there are no valves guarding the
junctions between the venae cavae and the right atrium or
the pulmonary veins and the left atrium.
• As the atria contract, a small amount of blood does flow
backward from the atria into these vessels.
• However backflow is minimized by a different mechanism;
as the atrial muscle contracts, it compresses and nearly
collapses the weak walls of the venous entry points.

Operation of Heart Valves
Figure 11.4

Blood Circulation
Figure 11.3

Systemic and Pulmonary Circulation

Systemic and Pulmonary Circulation
 In postnatal (aft er birth) circulation, the heart pumps
blood into two closed circuits with each beat—
systemic circulation and pulmonary circulation
(pulmon- = lung)
 The two circuits are arranged in series: The output
of one becomes the input of the other.
The left side of the heart is the pump for systemic
circulation; it receives bright red oxygenated (oxygen-rich)
blood from the lungs.

Systemic and Pulmonary Circulation
• The left side of the heart is the pump for systemic
circulation; it receives bright red oxygenated (oxygen-
rich) blood from the lungs.
• The left ventricle ejects blood into the aorta .
• From the aorta, the blood divides into separate streams,
entering progressively smaller systemic arteries that
carry it to all organs throughout the body—except for the
air sacs (alveoli) of the lungs, which are supplied by the
pulmonary circulation.
• In systemic tissues, arteries give rise to smaller-diameter
arterioles, which finally lead into extensive beds of
systemic capillaries.

Systemic and Pulmonary Circulation
• Exchange of nutrients and gases occurs across the thin
capillary walls. Blood unloads O2 (oxygen) and picks up
CO2 (carbon dioxide).
• In most cases, blood flows through only one capillary
and then enters a systemic venule. Venules carry
deoxygenated (oxygen-poor) blood away from tissues
and merge to form larger systemic veins.
• Ultimately the blood flows back to the right atrium.

Systemic and Pulmonary Circulation
• The right side of the heart is the pump for pulmonary
circulation; it receives all of the dark-red deoxygenated
blood returning from the systemic circulation. Blood
ejected from the right ventricle flows into the pulmonary
trunk, which branches into pulmonary arteries that carry
blood to the right and left lungs.
• In pulmonary capillaries, blood unloads CO2, which is
exhaled, and picks up O2 from inhaled air.
• The freshly oxygenated blood then flows into pulmonary
veins and returns to the left atrium.

Systemic and Pulmonary Circulation
• walls of the two ventricles with oxygenated blood. The marginal
branch beyond the coronary sulcus runs along the right margin
of the heart and transports oxygenated blood to the wall of the
right ventricle.
• parts of the body receive blood from branches of more than one
artery, and where two or more arteries supply the same region,
they usually connect. These connections, called anastomoses (a-
nas′-toˉ-MŌ-sēs), provide alternate routes, called collateral
circulation, for blood to reach a particular organ or tissue.
• .

Systemic and Pulmonary Circulation
• The myocardium contains many anastomoses that connect
branches of a given coronary artery or extend between branches
of different coronary arteries.
• They provide detours for arterial blood if a main route becomes
obstructed. This is important because the heart muscle may
receive sufficient oxygen even if one of its coronary arteries is
partially blocked.

Systemic and Pulmonary Circulation
• The right side of the heart is the pump for pulmonary
circulation; it receives all of the dark-red deoxygenated
blood returning from the systemic circulation. Blood
ejected from the right ventricle flows into the pulmonary
trunk, which branches into pulmonary arteries that carry
blood to the right and left lungs.
• In pulmonary capillaries, blood unloads CO2, which is
exhaled, and picks up O2 from inhaled air.
• The freshly oxygenated blood then flows into pulmonary
veins and returns to the left atrium.

Valve Pathology
• Incompetent valve = backflow and repump
• Stenosis = stiff= heart workload increased
• May be replaced
• Lup Dub Heart Sound

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

Coronary Circulation
 Blood in the heart chambers does not
nourish the myocardium
 The heart has its own nourishing
circulatory system
Coronary arteries
Cardiac veins
Blood empties into the right atrium via the
coronary sinus

• Nutrients are not able to diff use quickly enough from
blood in the chambers of the heart to supply all layers
of cells that make up the heart wall.
• For this reason, the myocardium has its own network
• of blood vessels, the coronary circulation or cardiac
circulation (coron- = crown).
• The coronary arteries branch from the ascending
aorta and encircle the heart like a crown encircles the
head.
• While the heart is contracting, little blood flows in the
• coronary arteries because they are squeezed shut.
• When the heart relaxes, however, the high pressure of
blood in the aorta propels blood through the coronary
arteries, into capillaries, and then into coronary veins
.

The principal tributaries carrying blood into the coronary
sinus are the following:
• Great cardiac vein in the anterior interventricular sulcus,
which
drains the areas of the heart supplied by the left coronary
artery (left
and right ventricles and left atrium)
• Middle cardiac vein in the posterior interventricular sulcus,
which
drains the areas supplied by the posterior interventricular
branch of
the right coronary artery (left and right ventricles)
• Small cardiac vein in the coronary sulcus, which drains the
right
atrium and right ventricle
• Anterior cardiac veins, which drain the right ventricle and
open
directly into the right atrium

The coronary circulation. The views of the heart from the
anterior aspect in (a) and(b) are drawn as if the heart were
transparent to reveal blood vessels on the posterior aspect.
The left and right coronary arteries deliver blood to the heart; the
coronary veins drain blood from

Cardiac Pathology
• Rapid heart beat
• = Inadequate blood
• = Angina Pectoris

The Heart: Conduction System
 Intrinsic conduction system
(nodal system)
Heart muscle cells contract, without nerve
impulses, in a regular, continuous way

The Heart: Conduction System
Special tissue sets the pace
Sinoatrial node (right atrium)
 Pacemaker
Atrioventricular node (junction of r&l atria
and ventricles)
Atrioventricular bundle (Bundle of His)
Bundle branches (right and left)
Purkinje fibers

The Heart: Conduction System
Cardiac action potentials propagate through the conduction
system in the following sequence :
• Cardiac excitation normally begins in the sinoatrial (SA)
node, located in the right atrial wall just inferior and
lateral to the opening of the superior vena cava. SA node
cells do not have a stable resting potential. Rather, they
repeatedly depolarize to threshold spontaneously. The
spontaneous depolarization is a pacemaker potential.
When the pacemaker potential reaches threshold, it
triggers an action potential . Each action potential from
the SA node propagates throughout both atria via gap
junctions in the intercalated discs of atrial muscle fibers.
Following the action potential, the two atria contract at
the same time.

The Heart: Conduction System
• By conducting along atrial muscle fibers, the action
potential reaches the atrioventricular (AV) node, located
in the interatrial septum, just anterior to the opening of the
coronary sinus. At the AV node, the action potential slows
considerably as a result of various differences in cell
structure in the AV node. This delay provides time for the
atria to empty their blood into the ventricles.
• From the AV node, the action potential enters the
atrioventricular (AV) bundle (also known as the bundle
of His, pronounced HIZ). This bundle is the only site
where action potentials can conduct from the atria to the
ventricles. (Elsewhere, the fibrous skeleton

The Heart: Conduction System
• Aft er propagating through the AV bundle, the action potential
enters both the right and left bundle branches. The bundle
branches extend through the interventricular septum toward
the apex of the heart.
• Finally, the large-diameter Purkinje fibers (pur-KIN-jē)
rapidly conduct the action potential beginning at the apex of
the heart upward to the remainder of the ventricular
myocardium. Then the ventricles contract, pushing the blood
upward toward the semilunar valves.

Heart Contractions

Heart Contractions

• Three formations
– P wave: impulse across atria
– QRS complex: spread of impulse down septum,
around ventricles in Purkinje fibers
– T wave: end of electrical activity in ventricles
Electrocardiograms (EKG/ECG)

Electrocardiograms (EKG/ECG)
(cont.)
Figure 8.15B, C

Electrocardiograms (EKG/ECG)
(cont.)

Pathology of the Heart
• Damage to AV node = release of ventricles from control = slower
heart beat
• Slower heart beat can lead to fibrillation
• Fibrillation = lack of blood flow to the heart
• Tachycardia = more than 100 beats/min
• Bradychardia = less than 60 beats/min

The Heart: Cardiac Cycle
 Atria contract simultaneously
 Atria relax, then ventricles contract
 Systole = contraction
 Diastole = relaxation

The Heart: Cardiac Cycle
 Atrial Systole = contraction(Systole During atrial
systole, which lasts about 0.1 sec , the atria are contracting. At
the same time, the ventricles are relaxed.)
• Ventricular Systole = relaxation(During
ventricular systole, which lasts about 0.3 sec, the ventricles are
contracting. At the same time, the atria are relaxed in atrial
diastole.)

The Heart: Cardiac Cycle
 Atrial Systole
1Depolarization of the SA node causes atrial depolarization,
marked by the P wave in the ECG.
2 Atrial depolarization causes atrial systole. As the atria contract,
they exert pressure on the blood within, which forces blood through
the open AV valves into the ventricles.
3 Atrial systole contributes a final 25 mL of blood to the volume
already in each ventricle (about 105 mL). The end of atrial systole is
also the end of ventricular diastole (relaxation). Thus, each ventricle
contains about 130 mL at the end of its relaxation period (diastole).
This blood volume is called the end-diastolic volume (EDV).
4 The QRS complex in the ECG marks the onset of ventricular
depolarization.

The Heart: Cardiac Cycle
 Ventricular Systole
5 Ventricular depolarization causes ventricular systole. As ventricular
systole begins, pressure rises inside the ventricles and pushes blood
up against the atrioventricular (AV) valves, forcing them shut. For
about 0.05 seconds, both the SL (semilunar) and AV valves are closed.
This is the period of isovolumetric contraction(ī-soˉ-VOL-ū-met′-rik;
iso- = same). During this interval, cardiac muscle fibers are contracting
and exerting force but are not yet shortening. Thus, the muscle
contraction is isometric (same length). Moreover, because all four
valves are closed, ventricular volume remains the same (isovolumic).
6 Continued contraction of the ventricles causes pressure inside the
chambers to rise sharply. When left ventricular pressure surpasses
aortic pressure at amillimeters of mercury (mmHg) and right ventricular
pressure rises above the pressure in the pulmonary trunk (about 20
mmHg), both SL valves openbout 80. At this point, ejection of blood
from the heart begins. The period when the SL valves are open is
ventricular ejection and lasts for about 0.25 sec. The pressure in the
left ventricle continues to rise

The Heart: Cardiac Cycle
 Ventricular Systole
to about 120 mmHg, and the pressure in the right ventricle climbs to
about 25–30 mmHg.
7 The left ventricle ejects about 70 mL of blood into the aorta and
the right ventricle ejects the same volume of blood into the
pulmonary trunk. The volume remaining in each ventricle at the end
of systole, about 60 mL, is the end-systolic volume (ESV). Stroke
volume, the volume ejected per beat from each ventricle, equals
end-diastolic volume minus end-systolic volume: SV = EDV − ESV.
At rest, the stroke volume is about 130 mL − 60 mL = 70 mL (a little
more than 2 oz).
8 The T wave in the ECG marks the onset of ventricular
repolarization.

The Heart: Cardiac Cycle
 Relaxation Period
• During the relaxation period, which lasts about 0.4 sec, the atria and
the ventricles are both relaxed. As the heart beats faster and faster, the
relaxation period becomes shorter and shorter, whereas the durations
of atrial systole and ventricular systole shorten only slightly.

The Heart: Cardiac Cycle
• Ventricular repolarization causes ventricular diastole. As the ventricles
relax, pressure within the chambers falls, and blood in the aorta and
pulmonary trunk begins to flow backward toward the regions of lower
pressure in the ventricles. Backflowing blood catches in the valve cusps
and closes the SL valves. The aortic valve closes at a pressure of about
100 mmHg. Rebound of blood off the closed cusps of the aortic valve
produces the dicrotic wave on the aortic pressure curve. Aft er the SL
valves close, there is a brief interval when ventricular blood volume
does not change because all four valves are closed. This is the period of
isovolumetric relaxation.
10 As the ventricles continue to relax, the pressure falls quickly. When
ventricular pressure drops below atrial pressure, the AV valves open, and
ventricular filling begins. The major part of ventricular filling occurs just
aft er the AV valves open. Blood that has been flowing into and building
up in the atria during ventricular systole then rushes rapidly into the
ventricles. At the end of the relaxation period, the ventricles are about
three-quarters full. The P wave appears in the ECG, signaling the start of
another cardiac cycle.

Cardiac cycle. (a) ECG. (b) Changes in left atrial pressure
(green line), left ventricular pressure (blue line), and aortic
pressure (red line) as they relate to the opening and closing of
heart valves. (c) Heart sounds. (d) Changes in left ventricular
volume. (e) Phases of the cardiac cycle.
A cardiac cycle is composed of all of the events associated with
one heartbeat

Filling of Heart Chambers –
the Cardiac Cycle
Slide
Figure 11.6

The Heart: Cardiac Output
 Cardiac output (CO)
Amount of blood pumped by each side of
the heart in one minute
CO = (heart rate [HR]) x (stroke volume
[SV])
 Stroke volume
Volume of blood pumped by each ventricle
in one contraction

Cardiac output, cont.
• CO = HR x SV
• 5250 ml/min = 75 beats/min x 70 mls/beat
• Norm = 5000 ml/min
• Entire blood supply passes through body once per minute.
• CO varies with demands of the body.

Cardiac Output Regulation
Figure 11.7

The Heart: Regulation of Heart
Rate
 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

Regulation of Heart Rate
 Increased heart rate
Sympathetic nervous system
Crisis
Low blood pressure
Hormones
Epinephrine
Thyroxine
Exercise
Decreased blood volume

The Heart: Regulation of Heart
Rate
 Decreased heart rate
Parasympathetic nervous system
High blood pressure or blood volume
Dereased venous return
In Congestive Heart Failure the heart is
worn out and pumps weakly. Digitalis
works to provide a slow, steady, but
stronger beat.

Congestive Heart Failure (CHF)
•Decline in pumping efficiency of heart
•Inadequate circulation
•Progressive, also coronary atherosclerosis, high
blood pressure and history of multiple Myocardial
Infarctions
•Left side fails = pulmonary congestion and
suffocation
•Right side fails = peripheral congestion and edema

Blood Vessels: The Vascular
System
 Taking blood to the tissues and back
Arteries
Arterioles
Capillaries
Venules
Veins

The Vascular System
Slide
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.8b

Blood Vessels: Anatomy
 Three layers (tunics)
Tunic intima
Endothelium
Tunic media
Smooth muscle
Controlled by sympathetic nervous
system
Tunic externa
Mostly fibrous connective tissue

Differences Between Blood Vessel
Types
 Walls of arteries are the thickest
 Lumens of veins are larger
 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

Movement of Blood Through
Vessels
 Most arterial blood is
pumped by the heart
 Veins use the milking
action of muscles to
help move blood
Figure 11.9

Capillary Beds
 Capillary beds
consist of two
types of vessels
Vascular shunt –
directly connects an
arteriole to a venule
Figure 11.10

Capillary Beds
True capillaries –
exchange vessels
Oxygen and
nutrients cross to
cells
Carbon dioxide
and metabolic
waste products
cross into blood
Figure 11.10

Diffusion at Capillary Beds
Figure 11.20

Vital Signs
• Arterial pulse
• Blood pressure
• Repiratory Rate
• Body Temperature
• All indicate the efficiency of the system

Pulse
 Pulse –
pressure wave
of blood
 Monitored at
“pressure
points” where
pulse is easily
palpated
Figure 11.16

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

Measuring Arterial Blood Pressure
Figure 11.18

Blood Pressure: Effects of Factors
 Neural factors
Autonomic nervous system adjustments
(sympathetic division)
 Renal factors
Regulation by altering blood volume
Renin – hormonal control

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

Variations 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)
Can be dangerous if it is chronic

Thank-You
Jagruti Marathe