CARDIOVASCULAR SYSTEM

CARDIOVASCULAR SYSTEM
 Is also called circulatory system
 Consist of heart (muscular pumping device)
& the vessels e.g. veins, arteries & capillaries
 It begins to beat regularly early in the fourth
week after fertilization
 It continually propels oxygen, nutrients,
wastes & many other substances into the
interconnecting blood vessel supplying body
organs

LOCATION OF THE HEART
 A four-chambered, shaped & sized like a
persons closed fist
 Lies in the mediastinum (middle region of the
thorax) behind the body of the sternum,
between the second rib to the fifth intercostal
space.
 Is about 12-14 cm

LOCATION (CONT.)
 Two third of its mass is to the left of the
midline of the body & one third is to the right
 Apex lie on the diaphragm, pointing to the left
 Apical pulse can be felt, this is caused by the
apex contracting the chest wall (on the fifth &
six rib)
 Base of the heart lie bellow the second rib

SIZE & SHAPE
 About size of the fist
 Hollow cone-shape
 It is broad, flat base or posterior surface
about 9cm
 At birth, it is transverse (wider) it appear
larger as oppose to the diameter of chest
cavity

SHAPE & SIZE (CONT.)
 Between puberty & 25yrs old, it attain its
adult shape & weight, about 310g for males
& 225g for females
 In adult, its shape resemble that of the chest
 For tall individuals, it is elongated, for short
ones is transverse (wide)

COVERING
 Is covered by the pericardium, which
consist of two parts
1. Fibrous portion: tough, loose fitting
inextensible sac. Its functions are as follows:
 Protect the heart
 Prevent overfilling of the heart with blood
 Anchor it to the surrounding structures.

PARTS OF PERICARDIUM (CONT.)
2. Serous portion: lies inside the fibrous
pericardium
 It is thin & slippery & consist of two layers
 Parietal layer lies inside the fibrous
pericardium & visceral layer adheres to the
outside of the heart
 Pericardial space (cavity) with pericardial
fluid separate the two layers

THE HEART (CONT.)
Functions of the heart covering
 Provides protection against friction

STRUCTURE/LAYERS OF THE HEART
Three distinct layers of tissue make up the
walls of the heart
o Epicardium: outer layer of the heart wall, it
is often infiltrated with fat in older people
o Myocardium: is thick, contractile middle
layer (layer that contracts). It compress the
heart activities and blood within them with
great force without fatigue

LAYERS (CONT.)
NB myocardium is thicker in some areas than
the other
o Endocardium: is a delicate inner layer of the
endothelial tissue (type of a membranous
tissue that lines the heart & blood vessels).
Endocardium regulate the flow of blood
through the chambers of the heart

CHAMBERS OF THE HEART
Is divided into four cavities
 Two upper chambers are called atria/atrium
 The lower chambers are called ventricles
NB: chambers are separated by the septum,
 Interatria septum (between the atria)
 Intervetricular septum (between the
ventricles)

ATRIA
 Called receiving chambers as they receive
blood from the veins (are 3, superior, inferior
vena cava & coronary sinus
 It alternately relax & contract to receive blood
then push it into the lower chamber
 They move blood to a small distance, don’t
need great pressure, so their myocardial wall
is not very thick

ATRIA
 Four pulmonary vein enter the left atrium (are
vein that transport blood from the lungs back
to the heart
 Auricle- earlike flap protruding from each
atrium

VENTRICLES
 Two lower chambers known as “pumping
chambers” or discharging chambers”
 They push blood to the large network of
blood vessels
 Are thicker than atria because great force is
needed to pump blood to a large distance
 Left ventricle is thicker than the right as it
push blood further

VENTRICLES (CONT.)
 Internal walls of ventricular chamber are
irregular ridges of muscle called trabeculae
carneae
 Right V pumps blood into pulmonary trunk
which transport the blood to the lungs
 Left V ejects blood to the aorta (which is the
largest artery (which is the largest artery in
the body)

VALVES OF THE HEART
 Are mechanical devices that permit the flow
of blood in one direction only (prevent back
flow)
 There are four sets of valves important to
normal functioning of the heart
I. Atrioventicular valves
II. Semilunar valves
III. Aortic semilunar
IV. Pulmonary semilunar valve

ATRIOVENTRICULAR VALVES
 The right AV orifice consist of the three flaps
(cup) of endocardium
 Is also called tricuspid valve
 Left AV orifice has two flaps (cup)
 Is also called bicuspid (mitral) valve
NB: AV valves prevent blood from flowing back
into the atria from the ventricle when it contract

SEMILUNAR VALVES
 Half moon-shaped flaps growing out from the
lining of the pulmonary artery & aorta
 SL valves prevent blood from flowing back
into the ventricles from the aorta &
pulmonary artery

VALVE (CONT.)
- Aortic semilunar valve: valve at the entrance
of the aorta
 Pulmonary semilunar valve: valve at the
entrance of pulmonary artery
NB: all the valves open & close in response to
the differences in pressure

FLOW OR PATHWAY OF BLOOD THROUGH HEART
 Has two side by side pumps (pulmonary &
systemic circuit)

BLOOD SUPPLY OF HEART TISSUE
How the blood get nourishment?
 It is regarded as a shortest circulation in the
body
 Myocardial cells receive blood right & left
coronary arteries(which branch from aorta &
via main branches)
 Ventricles receive blood from branches of
both right & left coronary arteries

BLOOD SYPPLY (CONT.)
 Most abundant blood supply goes to the
myocardium of the left ventricle because the left
ventricle does the most work & so needs the
most oxygen & nutrients delivered to it
 The right coronary supply the right side of the
heart, this artery branches into two, the right
marginal artery (supply the right side of the
heart) & posterior interventricular artery(which
run to the heart apex & supply posterior
ventricular wall)

BLOOD SUPPLY (CONT.)
 Few anastomoses (connections exist
between the larger branches of coronary
arteries. If main route become obstructed,
anastomoses provide collateral circulation to
a part. NB there will be inadequate supply of
nutrients
 Complete blockage leads to tissue death &
heart attack

CARDIAC VEINS(VEINS OF CORONARY
CIRCULATION)
 Veins follow a course that closely parallels
that of coronary artery
 After going through cardiac veins, blood
enters the coronary sinus to drain into the
right atrium
 Several veins drain directly into the right
atrium

CONDUCTION SYSTEM OF THE HEART
 Heart has intrinsic system, is automatically
stimulated without external stimulation
 Consist of four structures – Sinoatrial (SA)
node, Atrioventricular (AV) node,
Atrioventricular (AV) bundle & the Purkinje
fiber

CONDUCTION (CONT.)
 SA node (pace maker) : consist of hundreds
of cells located in the right atrial wall near the
opening of superior venacava
Functions
 Generate impulse about 75 times every
minute
 Sets the pace of the heart (determines the
heart rate), they possess an intrinsic rhythm

CONDUCTION (CONT.)
 This means that without any nerve impulses
from the brain & spinal cord, they themselves
initiate impulse at regular intervals.
 That means the firing of the SA node cause
atrial contraction
 AV node: small mass of special cardiac
muscle tissue, lie in the right atrium along the
lower part of the interatrial septum, is above
tricuspid valve

CONDUCTION (CONT.)
 As the action potential enter the AV node
from the right atrium, its conduction slows to
allow complete contraction of both atrial
chamber before the impulse reaches the
ventricle
 Meaning there is a delay here, electrical
signal takes 0,1 of a second to pass through
into the ventricle. This allows the atria to
finish contracting before ventricles starts

CONDUCTION (CONT.)
 AV bundle (bundle of His)- originate in AV node,
extend by two branches down the two sides on
the interventricular septum, & continue as a
purkinje fibers
 After passing slowly through the Av node,
conduction velocity increase as the impulse is
relayed through the AV bundle into the ventricles

CONDUCTION (CONT.)
 Here, right & left bundle branches and the
purkinge fibers in which they terminate
conduct the impulses throughout muscle of
both ventricles, stimulate them to contract
almost simultaneously
 Purkinge fibers extend out to the papillary
muscle & lateral wall of ventricles

CONDUCTION (CONT.)
 NB: SA node initiates each heartbeat & set
its pace- hence is called pace maker
 The SA node normally drives the heart at the
rate of 75 beats per minutes

NERVE SUPPLY TO THE HEART
 The heart is influenced by autonomic nerves
originating in the cardiovascular center in the
medulla oblongata which reach it through the
autonomic nervous system
 These consist of parasympathetic fibers
combine to form cardiac plexuses located
close to the arch of the aorta

NERVE SUPPLY (CONT.)
 The heart is influence by autonomic nerves
originating in the cardiovascular center in the
medulla oblongata which reach it through the
autonomic nervous system
 These consist of parasympathetic &
sympathetic nerve & their actions are
antagonistic

NERVE SUPPLY (CONT.)
 Both sympathetic fibers & parasympathetic
fibers combine to form cardiac plexus located
close to the arch of the aorta
 From the cardiac plexus, fibers accompany
the right & left coronary arteries to enter the
heart
 Most fibers end in the SA node, but some
end in the AV node & in the atria myocardium

NERVE SUPPLY (CONT.)
 The vagus nerves supply mainly the SA & AV
nodes & atria muscles. Parasympathetic
stimulation reduces the rate at which
impulses are produced, decreasing the rate
& force of heart beat called (inhibitory or
depressor nerves)

NEARVE SUPPLY (CONT.)
 The sympathetic nerve supply the SA & AV
node & myocardium of the atria & ventricles.
 Sympathetic stimulation increases the rate &
force of the heart beat (are called the
accelerator

ELECTROCARDIOGRAM (ECG)
 Is the graphic representation of cardiac
conduction cycle
 A graphic record of the heart electrical
activity, its conduction of impulses, a record
of electrical events that precedes the
conduction of the heart
 This record of electrical events must be
interpreted to make a difference between life
& death

TO PRODUCE ECG
 Electrodes of ECG are attached to a person
 Changes in voltages are recorded that
represent changes in the hearts electrical
activity, are observed as deflection of a line
drown on the paper or traced on the video
monitor

ECG (CONT.)
Normal ECG has three distinguishable wave or
deflection
 P wave: is the first & small wave, which
represent depolarization of the atria from the
SA node. Last at about 0.08second. 0.1
second after the P wave begins, the atria
contract

ECG (CONT.)
 QRS complex :represents depolarization of
the ventricles & repolarization of the atria.
That means the ventricle contracts & the
atria relaxes. Duration of QRS complex is
0.08 second

ECG (CONT.)
 T wave: represent repolarization of ventricles.
Duration of T wave last about 0.16 seconds.
Repolarization is slower than depolarization that
is why T wave has a lower height than QRS
wave
 NB: the measurement of the intervals between
P, QRS & T wave can provide information about
the rate of conduction of an action potential
through the heart

HEART SOUNDS
 One is not conscious of his heartbeat unless
he uses stethoscope below the left nipple to
hear the heart beat
 It make typical sound during each cardiac
cycle like “lubb-dupp”
 This is associated with the closing of heart
valves
 The pause between indicate period when the
heart is relaxing

HEART SOUND (CONT.)
 Systolic sound: first sound caused by the
contraction of the ventricles & by vibration of
closing Atrioventricular valves. It is longer
than diastolic sound
 Diastolic sound: is short, sharp sound
caused by vibrations of the closing of the
semiluner valve at the beginning of the
ventricular relaxation

HEART SOUND (CONT.)
NB: heart sounds have clinical significance
because they give information about the
functioning of the valves of the heart
Abnormal heart sounds called murmurs,
usually reflect valve problems

THE CARDIAC CYCLE
 The heart acts as a pump & its action
consists of a series of events known as the
cardiac cycle
 Cardiac cycle means a complete heat beat
 During each heart beat, the heart contracts &
then relaxes
 Period of contraction is called systole, that of
relaxation is called diastole of both atria
&both ventricles

CARDIAC CYCLE (CONT.)
NB: two atria contract simultaneously, then as
the atria relax, two ventricles contract and then
relax
Cardiac cycle include all events associated
with the blood flow through the heart during
one complete heat beat- atria systole & atria
diastole followed by ventricular systole &
diastole

PHASES OF CARDIAC CYCLE
 Phase 1 Atria systole
 Is the contraction of atria, there is a complete
emptying of blood out of the atria into the
ventricles
 AV valves are open during this phase,
semilunar valves are closed so that blood
does not re enter from pulmonary artery or
aorta

PHASE 1 (CONT.)
 Ventricles are relaxed & filling with blood
 The cycle begin with P wave of the ECG

CYCLE (CONT.)
 Phase 2 Isovolumetric ventricular contraction
 Occur between the start of ventricular systole
(contraction of the ventricles) and the
opening of semilunar valves
 The ventricular volume remain constant as
the pressure is increased rapidly

PHASE 2 (CONT.)
 The onset of ventricular systole coincides
with the R wave of the ECG & the
appearance of the first heart sound

CYCLE (CONT.)
 Phase 3 Ejection
 Semilunar valves open & blood is ejected
from the heart when the pressure gradient in
the pulmonary artery & aorta
 Reduced ejection is characterized by a less
abrupt decrease in ventricular volume.
coincide

PHASE (CONT.)
 Residual volume, normally remains in the
ventricles at the end of ejection period

CYCLE (CONT.)
 Phase 4 Isovolumetric ventricular relaxation
 Ventricular distole (relaxation) begin with this
phase
 Occurs between closure of the semilunar
valve & opening of AV