Cardiovascular system.ppt

Cardio-Vascular System
(Heart)
Malisawa, C.P. OTNS 1

Learning outcomes
• Explain an overview of the heart
• Location and associated organs of the heart
• Discuss the structure of the heart
• Explain the major vessels of the heart as seen
anteriorly or posteriorly
• Explain the mechanism of valves

Introduction
• The CVS comprise three interrelated
components namely heart, blood and
blood vessels.
• It is a closed system lined with
endothelium (a single layer of flat cells)
and filled with blood essential for
metabolic processes of all body cells.

Cont..
The CVS meets the increased demand
by increasing the blood flow to areas
of greater activity or to the entire
body if whole of it is involved.

The Heart.
• Approximately the size of owner’s fist.
• It’s hollow, cone-shaped that weighs less than a
pound (approx 225g in females and 310g in
males).
• The apex is pointed toward the left hip and rests
on the diaphragm, approximately at the level of
the 5th intercoastal space.
• It’s broader postero-superior aspect, the base,
from which the great vessels of the body emerge.

Cont..
• It pumps about 5litres of blood per minute to the
lungs and same amount to the rest of the body.
• The human heart essentially is two separate hearts
enclosed in a membrane called the pericardium.
• Fibrous tissues in the pericardium protect the heart
and anchor it to surrounding structures, such as the
diaphragm and sternum.
• It secretes a fluid that reduces friction as the heart
beats.

Location
• The heart is located within the
mediastinum.
• It rests on the superior surface of the
central tendon of the diaphragm, medial
to the lungs, anterior to the oesophagus
and vertebral column, and posterior to
the sternum.

ASSOCIATED ORGANS
• Inferiorly – Rests on the central tendon of the
diaphragm
• Superiorly – Aorta, superior vena cava,
pulmonary artery and veins
• Posteriorly – Oesophagus, trachea, left and
right bronchus, descending aorta, inferior
vena cava and thoracic vertebrae
• Laterally – Lungs
• Anteriorly – Sternum, ribs and intercoastal
muscles

Parts of the Heart
• Pericardium
• Myocardium
• Endocardium

PERICARDIUM
• A double-walled fibrous superficial layer.
• A collagenous structure that anchors the
heart and prevents it from over
distension.
• The serous pericardium, is a 2 layered
serous membrane.
• The parietal pericardium is the outer of
the 2 and the viscera lines the inner
surface of fibrous pericardium.

Cont..
• The visceral pericardium is a.k.a. the
epicardium.
• The parietal and visceral layers are
continuous with one another where
the great vessels leave the heart.

MYOCARDIUM
• The bulk of the heart wall is composed of
cardiac muscle.
There are 2 types of cardiac muscle cells.
1. The contractile cells (99%) generate the force
involved in pumping.
2. The autorhythmic cells (1%) spontaneously
depolarize to set the rate of contraction.
• They are involuntary and are linked to one
another and to the autorhythmic cells by
intercalated discs.

Cont..
• Intercalated discs consist of 2 separate
structures: Gap junctions and Desmosomes.
• Gap junctions are protein channels that allow
ions to flow between adjacent cells.
• They amount to an electrical connection
between cardiac muscle cells.
• They allow the depolarization wave initiated
by autorhythmic cells to spread through the
cardiac musculature.

Cont..
• The heart function as a single coordinated unit (a
functional syncytium), which helps maximize its
efficiency.
• Desmosomes physically connect adjacent cardiac
muscle cells. This prevents cells from separating
during contraction.
• Electrical excitation of cardiac muscle cells
causes an increase in intracellular Ca²⁺levels.
Calcium binds with troponin to produce
contraction via the familiar sliding filament
mechanism.

Cardiac muscle

ENDOCARDIUM
The endocardium is a thin inner,
glistening sheet of endothelium (simple
squamous epithelium) that lines the
heart chambers, valves and helps blood
flow smoothly through the heart.
• It is continuous with the linings of the
blood vessels leaving and entering the
heart.

External heart: major vessels of the heart (anterior
view)
Returning blood to the heart
• Superior and inferior venae cavae
• Right and left pulmonary veins
Conveying blood away from the heart
• Pulmonary trunk, which splits into right and
left pulmonary arteries
• Ascending aorta (three branches) –
brachiocephalic, left common carotid, and
subclavian arteries

External heart: vessels that supply/drain the heart
(anterior view)
• Arteries – right and left coronary (in
• interventricular groove), marginal, circumflex,
and anterior interventricular
• Veins – small cardiac vein, anterior cardiac
vein, and great cardiac vein

External heart: major vessels of the heart
(posterior view)
Returning blood to the heart
• Right and left pulmonary veins
• Superior and inferior venae cavae
Conveying blood away from the heart
• Aorta
• Right and left pulmonary arteries

External heart: vessels that supply/drain the heart (posterior
view)
• Arteries – right coronary artery (in
atrioventricular groove) and the posterior
interventricular artery (in interventricular
groove)
• Veins – great cardiac vein, posterior vein to
left ventricle, coronary sinus, and middle
cardiac vein

INTERIOR OF THE HEART.
• Frontal section showing interior chambers and
valves.
• Major vessels leading to and from the heart
• The heart is divided in to a right and left side
by the septum; this is a partition consisting of
myocardium covered by endocardium.

Cont..
• Each side is divided by an atrioventricular
valve into upper and lower chambers; these
atrioventricular valves are formed by double
folds of endocardium strengthened by fibrous
tissue.

Cont..
The valves are prevented from opening upwards
in to the atria by tendinous cords called
chordae tendineae.

Cont..
• Atria of the Heart which are the receiving
chambers of the heart with a protruding
auricle (pouch) each, Blood enters right atria
from superior and inferior venae cavae and
coronary sinus, Blood enters left atria from
pulmonary veins
• Pectinate muscles mark atrial walls.

VENTRICLES OF THE HEART
• Ventricles are the discharging chambers of the
heart
• Papillary muscles and trabeculae carneae
muscles mark ventricular walls
• Right ventricle pumps blood into the
pulmonary trunk.
• Left ventricle pumps blood into the aorta.

THE HEART VALVES
The two atrioventricular valves prevent backflow
into the atria when the ventricles contract:
• The left AV-valve/ the bicuspid or mitral valve
consists of two cusps, or flaps, of
endocardium.
• The right AV-valve/ the tricuspid valve has
three cusps.
The two semilunar valves close the two large
arteries as the ventricles relax:
• The right SL-valve and the aortic valve has
three cusps that fit tightly together.

Mechanism
• The valves of the heart and great vessels open
and close depending on the level of pressure
within the vessels/chambers of the heart.
• AV valves are open while ventricular muscles
are relaxed during atrial filling and systole.
• When the ventricles contract the pressure in
these chambers increase insidiously and as it
rises above atria pressure the AV valves closes.

Cont..
• When the ventricular pressure rises
above that of the pulmonary and aortic
pressure, the SL valve opens and blood
flows in to the great vessels.
• When the ventricles relax and the
pressure within them falls, the reverse
happens.

Learning outcomes
• Explain an overview of the heart
• Location and associated organs of the heart
• Discuss the structure of the heart
• Explain the major vessels of the heart as seen
anteriorly or posteriorly
• Explain the mechanism of valves

END OF PART ONE
•END OF PART
ONE

Learning outcomes
• Overview of coronary circulation
• Pulmonary and systemic circulation
• Discuss the cardiac conduction system
• Explain the cardiac cycle and electric changes
• State the heart sounds
• Outline the cardiac output
• State factors affecting stroke volume
• Factors affecting heart rate
• Functions of the heart and valves

CORONARY CIRCULATION
• Coronary circulation is the functional blood supply to
the heart which is about 5% of the total body needs.
• Collateral routes insure blood delivery to heart even
if major vessels are occluded.
• Although the heart chambers are continuously
bathed with blood, the blood contained in the heart
does not nourish the myocardium.
• The blood supply that oxygenates and nourishes the
heart is provided by the right and left coronary
arteries.

Cont..
• The coronary arteries branch from the base of
the aorta and encircle the heart in the
atrioventricular groove at the junction of the
atria and ventricles.
• They are compressed when the ventricles are
contracting and fill when the heart is relaxed.
• The myocardium is drained by several cardiac
veins, which empty into an enlarged vessel on
the backside of the heart called the coronary
sinus. Which in turn, empties into the right
atrium.

Pathway of blood through the heart
and lungs
• Right atrium via tricuspid valve to a right
ventricle
• Right ventricle via pulmonary semilunar valve
to pulmonary trunc, arteries to lungs
• Lungs to pulmonary veins to left atrium
• Left atrium via bicuspid valve to left ventricle
• Left ventricle to aortic semilunar valve to
aorta
• Aorta to systemic circulation

HEART MUSCLE CONTRACTION/CONDUCTING
SYSTEM
• The heart consists of muscle cells that
contract in waves.
• When the first group is stimulated, they in
turn stimulate neighboring cells.
• This chain reaction continues until all cells
contract.
• The wave of activity spreads in such a way
that the atria and the ventricles contract in a
steady rhythm.

SINOATRIAL NODE
• The wave begins in a small bundle of
specialized heart muscle cells embedded in
the right atrium near the opening of the
superior vena cava called the sinoatrial node
(SA).
• The SA-node is the natural pacemaker of the
heart.
• It initiates each heartbeat, without stimulation
from the nervous system, and sets the pace
for the heart rate.

Cont..
• The impulse spreads from the pacemaker
through the cardiac muscle cells in the
right and left atrium, causing both atria
to contract almost simultaneously.
• Then the impulse initiated by the SA-
node reaches another special area of the
heart known as the atrioventricular (AV)
node.

ATRIOVENTRICULAR NODE
• The AV-node is located in the septum
between the right and left atrium near the
atrioventricular valve (posterior wall).
• The AV-node relays the electrical impulse to
the muscle cells that make up the ventricles.
• The ventricles contract almost simultaneously
a fraction of a second after the atria
completing one full heartbeat.

Cont..
• This allows the atria to finish contracting
before the ventricles start. These contractions
cause the chambers to squeeze the blood,
pushing it in the proper direction along its
path.
• The AV node is a secondary pacemaker, takes
over from the SA if it has a problem with
transmission of impulses, however; the
intrinsic firing rate is slower than that of the
SA.

Atrioventricular bundle (AV bundle or bundle of His)
• Mass of specialised fibres with origins from
the AV node and passes the fibrous ring
(septum).
• It divides in to left and right bundle branches
at the upper end of the ventricular septum.
• It breaks in to fine fibres within the
ventricular myocardium to form purkinje
fibres.
Malisawa, C.P. OTNS
15

Cont..
• All the these structures convey electrical
impulses from the AV node to the apex of the
myocardium, to start the wave of ventricular
contraction that sweeps upwards and
downwards, pumping blood in to the
pulmonary trunk and aorta.

NERVE SUPPLY
• A.N. from the cardiovascular centre -
medulla oblongata, it consist of
parasympathetic and sympathetic
nerves with antagonistic actions
• Vagus nerves (parasympathetic)
supply mainly the SA and AV nodes
as well as atrial muscle.

Cont..
• Parasympathetic stimulation reduces the rate
at which impulses are produced, decreasing
the rate and force of the heart beat.
• The sympathetic nerves supply the SA and AV
as well as the myocardium of atria and
ventricles.
• It increases the rate and force of the heart
beat.

CARDIAC CYCLE
• In its simplest form, the cardiac cycle is the
simultaneous contraction of the two atria, followed a
fraction of a second later by the simultaneous
contraction of the two ventricles, it is the sequence
of events in one heartbeat.
A heartbeat has two phases:
• Phase 1 - Systole - Contraction.
• Occurs when the ventricles contract, closing the AV
valves and opening the SL valves to pump blood into
two major vessels leaving the heart.
• Phase 2 - Diastole - Relaxation.

STAGES OF CARDIAC CYCLE
Normal number of cycles per minute ranges
from 60 to 80 each last about 0.8 of a second
and consist of:
• Atrial systole -0.1 seconds
• Ventricular systole -0.3 seconds
• Complete cardiac diastole – 0.4 seconds
• The cycle could start at any stage.

Cont..
• The atrioventricular valves are open and blood
flows passively through to the ventricles.
• The SA node triggers a wave of contraction
that spreads over the myocardium, emptying
the atria and completing ventricular filling
(atrial systole 0.1 s)
• As the electrical impulse reaches the AV node
it is delayed to allow atria to finish emptying
in to the ventricles before the ventricles could
contract.

Cont..
• An AV node triggers its own electrical impulse,
which quickly spreads to the ventricular
muscle via the AV bundle.
• This causes a wave of contraction to sweep
upwards from apex causing ventricles to pump
blood in both the aorta and pulmonary artery
(ventricular systole 0.3 s)
• After contraction of the ventricles there is
complete cardiac diastole, a period of 0.4 s,
when atria and ventricles relax, the
myocardium recovers in preparation for the
next heart beat, and atria refill for the next
cycle.

Electrical changes in the heart.
• Body fluids and tissues are good conductors of
electricity, this activity within the heart can be
detected by attaching electrodes to the
surface of the body and this could be traced
on an electrocardiogram (ECG).
• This shows five waves namely P,Q,R.S and T.
• P – Wave arises when impulse from SA node
sweeps over the atria (atria depolarisation)

Cont..
• QRS complex – Rapid spread of impulse from
AV node through the AV bundle and the
purkinje fibres as well as electro activity of the
ventricular muscle (ventricular
depolarisation).
• T – Relaxation of the ventricular muscle
(ventricular repolarisation).

HEART SOUNDS
• Each heartbeat produces two sounds, often
called lubb-dub that can be heard with a
stethoscope.
• The first sound (S1), the loudest and longest, is
caused by the ventricular systole (contraction)
closing the AV valves.
• The second sound (S2) is caused by the closure
of the aortic and pulmonary valves (SL).

Cont..
• Third heart sound (occasional)
– Caused by turbulent blood flow into ventricles and
detected near end of first one-third of diastole
• If any of the valves do not close properly, an
extra sound called a heart murmur may be
heard.

Areas of auscultation

CARDIAC OUTPUT
• Cardiac Output (CO) is the amount of blood
pumped out of each side of the heart (each
ventricle) in 1 minute.
• It is the product of the heart rate (HR) and the
stroke volume (SV).
• Stroke volume is the volume of blood pumped
out by a ventricle with each heartbeat.

Cont..
• In general, stroke volume increases as the
force of ventricular contraction increases.
• Using the normal resting values for heart rate
(75 beats per minute) and stroke volume (70
ml - per beat), the average adult cardiac
output can be easily figured.
• CO = HR X SV
• CO = (75 beats / min) ( 70 ml / beat)
• CO = 5250 ml / min

Regulating stroke volume:
• A healthy heart pumps out about 60% of the
blood that enters it.
• The critical factor controlling stroke volume is
how much cardiac muscle cells are stretched
just before they contract.
Other factors:

Cont..
• Venous return, the amount of blood entering
the heart and distending its ventricles, is the
determining factor.
• Anything that increases the volume or speed
of venous return also increases stroke volume
and force of contraction.
• A slow heartbeat allows more time for the
ventricles to fill.

Cont..
• Exercise speeds venous return because it results in
increased heart rate and force.
• The enhanced squeezing action of active skeletal
muscles on veins returning blood to the heart, called
muscular pump, also plays a major role in increasing
venous return.
• On the other hand, low venous return, such as might
result from severe blood loss or an extremely rapid
heart rate, decreases stroke volume, causing the
heart to beat less forcefully.

REGULATING HEART RATE:
• For most of us, at rest our heart beats
between 60 and 80 beats per minute.
• Under certain conditions, that number can
increase to as many as 200 beats per minute.
• The sympathetic nervous system increases
heart rate.

Cont..
• During times of physical or emotional stress,
the SA-node and AV-node - and even the
cardiac muscle itself - can be stimulated to
increase heart rate.
• The parasympathetic nervous system
decreases it.
• When demand declines, the vagus nerves
slow and steady the heart.

Cont..
• Various hormones and ions can have a
dramatic effect on heart rate.
• Reduced Ca ²⁺ in the blood depress the heart,
while a low level of K⁺ causes the heart to beat
feebly and without rhythm.
• Gender – the heart rate is faster in women
than men

Cont..
• Autonomic nerve activity – the intrinsic rate at
which the heart beats is a balance between
sympathetic and parasympathetic activity and
this is the most important factor in
determining heart rate
• Age – in babies and small children the heart
rate is more rapid than in older ones and
adults

Cont..
• Hormones such as adrenaline, thyroxine –
have same effects as sympathetic
stimulation, they increase heart rate.
• Activity and exercise – active muscle need
more blood than resting ones which is
achieved by increased heart rate.

Cont..
• Temperature – rises and falls with change in
temperature may affect heart rate.
• Emotional stress – excitement, fear or
anxiety increases heart rate.

Cont..
• Baroreceptor reflex – the baroreceptors are
nerve endings sensitive to pressure changes
(stretch) within vessels, situated in the arch of
the aorta and the carotid sinuses and body’s
principal moment to moment regulatory
mechanism for controlling blood pressure e.g.
a rise in blood pressure leads to increase
parasympathetic activity to the heart which
slows the heart down.

Functions of the heart and valves
• Generating blood pressure
• Routing blood
– Heart separates pulmonary and systemic
circulations
Ensuring one-way blood flow
– Heart valves ensure one-way flow
Regulating blood supply
– Changes in contraction rate and force match
blood delivery to changing metabolic needs

Learning outcomes
• Overview of coronary circulation
• Pulmonary and systemic circulation
• Discuss the cardiac conduction system
• Explain the cardiac cycle and electric changes
• State the heart sounds
• Outline the cardiac output
• State factors affecting stroke volume
• Factors affecting heart rate
• Functions of the heart and valves

PART THREE
3

Learning Outcomes
• Give an overview of arteries
• The structure of arteries
• Outline the types of arteries
• Discuss capillaries and veins
• State the functions of blood vessels

BLOOD VESSELS
• Blood vessels are the tubes through which the
heart pumps blood. There are 3 major types
of blood vessels: arteries, capillaries, and
veins.
Overview
• Arteries take blood away from the heart. As
they move away from the heart, they branch
repeatedly,

Cont..
forming smaller and smaller arteries and
eventually the smallest arteries – the
arterioles. Arteries typically carry oxygenated
blood (except– the pulmonary arteries).
• Capillaries are the smallest and most
numerous vessel type. They are the sites of
exchange between blood and tissue fluid.

Cont..
• Exchange is facilitated by their thinness and
vast number. They “connect” arteries and
veins.
• Veins take blood toward the heart. As they
move toward the heart, they converge and
join, forming larger and larger vessels. The
smallest veins are the venules, which receive
blood from capillaries.

Cont..
• Veins typically carry deoxygenated blood
(except – the pulmonary veins).

Structure
• Arteries and veins have 3 basic layers or tunics
that surround a central blood-containing
space, the lumen.
• They are the: tunica interna, tunica media,
and tunica externa.
• Capillaries contain only the tunica interna.

Tunica interna
• The tunica interna is a.k.a. the tunica
intima.
• It lines the lumen and consists primarily of
endothelium.
• This helps provide a smooth surface ideal
for fluid flow.

T media
• The tunica media consists of circularly
arranged smooth muscle cells and sheets of
the protein elastin.
• The smooth muscle tone is regulated by
vasomotor fibres of the sympathetic nervous
system, hormones, and certain local
chemicals. An increase in tone leads to
vasoconstriction. A decrease in tone leads to
vasodilation

Cont
• There is a tonic release of NE onto vascular
smooth muscle by vasomotor neurons.
• Increasing NE release causes smooth muscle
contraction (vasoconstriction).
• Decreasing NE release causes smooth muscle
relaxation (vasodilation).
• The tunica media is the most prominent layer
in arteries.

T externa
• Tunica externa is a.k.a. tunica adventitia.
• It consists of mostly collagen fibres that
protect, reinforce, and support the vessel.
• It is the most prominent layer in veins.

Types of arteries
• Elastic arteries are a.k.a. conducting arteries
(elastic tissue in all 3 layers).
• They are the arteries closest to the heart, e.g.,
the aorta and its major branches (e.g.,
femoral, common carotids, etc.).
• Elastic tissues allow vessels to absorb the
surges of pressure associated with each
ventricular contraction.

Cont..
• Muscular arteries are a.k.a. distributing
arteries.
• They are primarily involved in regional
distribution of blood, i.e., delivery of blood to
specific organs (e.g., splenic artery, renal
artery, etc.).
• They contain a very thick tunica media.

Cont..
• Arterioles are the smallest vessels of the
arterial tree.
• Large arterioles have all 3 tunics.
• Smaller ones may only have smooth muscle
cells circling an endothelium.
• They are very important in regulation of blood
pressure and flow.

Cont..
• all the artery types are innervated to the
greatest extent by sympathetic vasomotor
fibres.
• Thus their level of muscle tone is the most
adjustable and the most often adjusted.

Capillaries
• They contain only a tunica interna.
• There are billions of capillaries in the human
body.
• This presents a huge surface area for
exchange.
• They’re arranged in networks (beds) and are
in rich supply in metabolically active tissues,
e.g., lungs, liver, kidneys, skeletal muscle and
cardiac muscle.

Cont..
• They’re absent in epithelia, cartilage, and the
corneas and lenses of the eyes.
• They’re quite thin, which also facilitates
exchange.

Capillaries

Types of capillaries
• Continuous capillaries are the most common
type and are abundant in skin and muscle.
• They are “continuous” in terms of each cell
(i.e., no holes within the cell membrane).
• Intercellular clefts may be found between
cells.
• Continuous capillaries are found in areas
where exchange of large items is unnecessary.

Cont..
• Fenestrated capillaries are similar to
continuous except the membranes of the
endothelial cells are riddled with pores
(fenestrations).
• They also contain intercellular clefts.
• They are much more permeable than
continuous capillaries. They are found in sites
of active absorption (e.g., intestines) or filtrate
formation (e.g., glomeruli of the kidney).

Cont..
• Sinusoidal capillaries are highly modified, very
permeable capillaries found in liver, bone
marrow, lymphoid tissues, and some
endocrine organs.
• They’re fenestrated and contain huge
intercellular clefts. Large molecules and even
blood cells can exit/enter.

Cont..
• They’re twisty, which slows down blood flow.
• Macrophages can form portions of the
capillary lining in the liver so as to monitor the
blood for bacteria and other undesirables.
• Capillaries form interconnected networks
known as capillary beds /rete.
• Capillary beds are bounded by an arteriole
and venule.

Cont..
• Venules are formed when capillaries unite.
• They coalesce (unit) to form small veins.
• Veins contain all 3 tunics, but in different
proportions than arteries.
• The most prominent layer is the tunica
externa.
• The walls of veins are thin and their lumens
are large. They have very low resistance and
are extremely compliant.

Cont..
• Venous muscle tone (the contraction of the
tunica media as controlled by the SNS)
prevents the veins from being distended too
much.
• Venous blood pressure is quite low because
they are so far from the pumping action of the
heart.

Cont..
• The low BP necessitates venous valves
(extensions of endothelium reminiscent
[significant] of the cardiac semilunar valves) to
prevent backflow.
• There are far more valves in the lower
extremities than the upper extremities.

Functions
• Heart ,arteries and veins can be regarded as
mainly specialised plumbing design to optimal
blood flow thru the capillaries
• Transport oxygen from the lungs, nutrients
from the gut
• Carry waste product from the tissues to the
lungs, kidneys and to a lesser extent to the gut
and skin for excretory

Cont..
• Carries and regulate substance from the
endocrine gland to their target tissues
• Carries heat between the body’s core and its
surface
• Carry cells and chemical factors that defends
the body against foreign substances and
organisms
• Capillaries function is that of diffusion and
absorption

Learning Outcomes
• Give an overview of arteries
• The structure of arteries
• Outline the types of arteries
• Discuss capillaries and veins
• State the functions of blood vessels

Thankyou
Good day

Cardiovascular system.ppt

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