Cardiovascular system ppt

HEART
The heart is a roughly cone-shaped hollow muscular
organ found in all animals and human beings with a
circulatory system, that is responsible for pumping
blood throughout the blood vessels by repeated,
rhythmic contractions. The term cardiac means
"related to the heart" and comes from the Greek
word, kardia, for "heart".
The human heart is about the size of a fist and has a
mass of between 250 and 300 grams. It is about 10
cm long and located slightly left of middle in the
chest, anterior to the vertebral column and posterior
to the sternum.

POSITION OF HEART
The heart situated in thoracic cavity in mediasternum, the space
between the lungs. It lies little more to the left than the right, and have
base above and an apex below. The apex is about 9 cm to the left of the
midline at the level of the 5th intercostal space, little below the nipple
and slightly nearer the midline. The base extends to the level of the 2nd
rib.
ORGANS ASSOCIATED WITH THE HEART:
Inferiorly: central tendon of the diaphragm
Superiorly: the great blood vessels; aorta, superior venacova,
pulmonary artery and vein.
Posteriorly: oesophagus, trachea, bronchus, descending aorta
Laterally: the lungs
Anteriorly: the sternum, ribs and intercostal muscle.

STRUCTURE OF THE HEART
The heart is composed of three layers of tissue pericardium,
myocardium and endocardium;
Pericardium: The pericardium is a triple-layered fluid-filled sac
that surrounds the heart. The outer layer of this sac is the fibrous
pericardium. It is a strong layer of connective tissue. It adheres
to the diaphragm inferiorly, and superiorly it is fused to the roots
of the great vessels that leave and enter the heart. The fibrous
pericardium acts as a tough outer coat that holds the heart in
place and keeps it from overfilling with blood. Deep to the
fibrous pericardium is the double layered serous
pericardium. The serous pericardium is a closed sac sandwiched
between the fibrous pericardium and the heart. The outer layer
is the parietal layer of the serous pericardium and adheres to the
inner surface of the fibrous pericardium. The parietal layer is
continuous with the visceral layer of the serous pericardium,
which lies on the heart and is considered a part of the heart wall.

Myocardium: The myocardium is the basic muscle that
makes up the heart. This muscle is involuntary. The cardiac
muscle structure consists of basic units of cardiac muscle
cells known as myocytes. Coordinated contraction of the
cardiac muscles is what makes the heart propel blood to
various parts of the body. It is the function of the coronary
arteries to supply blood and oxygen to the cardiac muscles.
This is the thickest of all the layers of the heart. The cardiac
muscles cannot afford to rest even for a single second So, it is
absolutely essential that these muscles get blood supply and
nutrition continuously, as any kind of disruption in the blood
and nutrition supply to these muscles can result in death of a
part of the cardiac muscle, which is known as myocardial
infarction or heart attack. This could in turn lead to a
complete cessation of functioning of the heart muscles,
known as cardiac arrest.

Endocardium: The endocarium is the innermost, thin and
smooth layer of epithelial tissue that lines the inner surface
of all the heart chambers and valves. This layer is made of
thin and flat cells that are in direct contact with the blood
that flows in and out of the heart. Each heart valve is formed
by a fold of endocardium with connective tissue between the
two layers. However, rather than just being an inner lining of
the heart, the endocardium also has an endocrine function.
This is one of the only layers of the heart that has a single
cell lining that secretes the hormone endocardin, which is
responsible for prolonging myocardial contraction.

CHAMBERS OF HEART
The heart is a hollow organ divided into four chambers:
 Right atrium
 Right ventricle
 Left atrium
 Left ventricle

The heart is divided into a right and left side by the septum. After
birth blood can not pass through the septum from one side to
another side. Each side is divided by an atrioventricle valve into
an upper chamber , the atrium and lower chamber, the ventricle.
The atrioventricular valves are formed by double folds of
endocardium. The heart consists of four chambers in which blood
flows. Blood enters the right atrium and passes through the right
ventricle. The right ventricle pumps the blood to the lungs where
it becomes oxygenated. The oxygenated blood is brought back to
the heart by the pulmonary veins which enter the left atrium.
From the left atrium blood flows into the left ventricle. The left
ventricle pumps the blood to the aorta which will distribute the
oxygenated blood to all parts of the body.

1. Right Atrium
The right atrium is a broad, triangular structure. The superior
vena cava opens into dome of right atrium and the inferior
vena cava into its lower posterior part. It is an extensive
muscular pouch projects anteriorly to overlap the right side
of the ascending aorta. Anteriorly, the right atrium is related
to the anterior part of the surface of the right lung. Laterally,
it is related to the surface of the right lung.

The interior surface of the right atrium can be divided a
smooth-walled venous component posteriorly, the vestibule
of the tricuspid valve. The wall of the vestibule is smooth, but
its junction with the auricle is ridged all around the
atrioventricular junction. The smooth-walled part receives
the opening of the venae cavae and the coronary sinus. It
represents the venous component. The wall of the vestibule
has a ridged surface.

The coronary sinus opens into the atrial component between
the orifice of the inferior vena cava, and the vestibule of the
atrioventricular opening. Coronary sinus is often guarded by
a thin, semicircular valve.

2. Right Ventricle
The right ventricle extends from the right atrioventricular
(tricuspid) orifice nearly to the cardiac apex. It then reaching
the pulmonary orifice and supporting the cusps of the
pulmonary valve. The ventricle possesses an inlet component
which supports and surrounds the tricuspid valve.

3. Left Atrium
Although smaller in volume than the right, the left atrium
has thicker walls (3 mm on average). Its cavity and walls are
formed largely by the proximal parts of the pulmonary veins.
The left atrium is roughly cuboidal and extends behind the
right atrium, separated from it by the obliquely positioned
septum. The left part is concealed anteriorly by the initial
segments of the pulmonary trunk and aorta.
Anteroinferiorly, and to the left, it adjoins the base of the left
ventricle at the orifice of the mitral valve.

4. Left Ventricle
The left ventricle is constructed in accordance with its role as
a powerful pump that sustains the high-pressured systemic
arteries. Its long axis descends forwards and to the left. Its
cavity is oval or nearly circular, with walls about three times
thicker (8–12 mm) than those of the right ventricle. The left
ventricle has an inlet region, guarded by the mitral valve, an
outlet region, guarded by the aortic valve. The left
atrioventricular orifice admits atrial blood during diastole,
flow being towards the cardiac apex. After closure of the
mitral cusps, and throughout the ejection phase of systole,
blood is expelled from the apex through the aortic orifice.

VALVES OF HEART
Every opening between the chambers and into the vessels is
supplied with a valve that protects backward flow of blood.
 The two Atrioventricular (AV) valves , which are between
the atria and the ventricles;
I. Mitral valve
II. Tricuspid valve
 The two Semilunar (SL) valves, which are in the arteries
leaving the heart;
I. Aortic valve
II. Pulmonary valve

Atrioventricular (AV) valves: These are small valves that
prevent backflow from the ventricles into the atrium during
systole. They are anchored to the wall of the ventricle by
chordae tendineae, which prevent the valve from inverting.
The chordae tendineae are attached to papillary muscles that
cause tension to better hold the valve. Together, the papillary
muscles and the chordae tendineae are known as the
subvalvular apparatus. The function of the subvalvular
apparatus is to keep the valves from prolapsing into the atria
when they close. The subvalvular apparatus have no effect
on the opening and closure of the valves, however. This is
caused entirely by the pressure gradient across the valve.
The closure of the AV valves is heard as the first heart
sound (S1).

I. Mitral valve: Also known as the "bicuspid valve"
contains two flaps. It allows the blood to flow from the
left atrium into the left ventricle. It is on the left side of
the heart and has two cusps. A common complication
of rheumatic fever is thickening and stenosis of the
mitral valve.

II. Tricuspid valve: The tricuspid valve is the three-flapped
valve on the right side of the heart, between the right
atrium and the right ventricle which stops the backflow of
blood between the two. It has three cusps.

Semilunar valves: These are located at the base of both the
pulmonary trunk (pulmonary artery) and the aorta, the
two arteries taking blood out of the ventricles. These
valves permit blood to be forced into the arteries, but
prevent backflow of blood from the arteries into the
ventricles. These valves do not have chordae tendineae,
and are more similar to valves in veins than
atrioventricular valves.

I. Aortic valve: The aortic valve lies between the left ventricle
and the aorta. The aortic valve has three cusps. During
ventricular systole, pressure rises in the left ventricle.
When the pressure in the left ventricle rises above the
pressure in the aorta, the aortic valve opens, allowing blood
to exit the left ventricle into the aorta. When ventricular
systole ends, pressure in the left ventricle rapidly drops.
When the pressure in the left ventricle decreases, the aortic
pressure forces the aortic valve to close. The closure of the
aortic valve cause second heart sound (S2). The most
common congenital abnormality of the heart is the
bicuspid aortic valve. In this condition, instead of three
cusps, the aortic valve has two cusps. This condition is
often undiagnosed until the person develops calcific aortic
stenosis. Aortic stenosis occurs in this condition usually in
patients in their 40s or 50s, an average of over 10 years
earlier than in people with normal aortic valves.

II. Pulmonary valve: The pulmonary valve (sometimes
referred to as the pulmonic valve) is the semilunar valve
of the heart that lies between the right ventricle and the
pulmonary artery and has three cusps. Similar to the
aortic valve, the pulmonary valve opens in ventricular
systole, when the pressure in the right ventricle rises
above the pressure in the pulmonary artery. At the end of
ventricular systole, when the pressure in the right
ventricle falls rapidly, the pressure in the pulmonary
artery will close the pulmonary valve. The closure of the
pulmonary valve cause second heart sound (S2).

STRUCTURE OF VALVE
Heart valves are made up of
flaps of thin, strong, tissue
attached to the heart with
fibrous cords called as
cusps. They can only open
in one direction. Valves
have two functions. They
allow blood to flow
through them smoothly
and prevent it from leaking
back against this flow.
Valves allow blood to flow
in one direction only.

1. Chordae Tendineae: The
chordae tendineae, or heart
strings, are cord-like tendons
that connect the papillary
muscles to the tricuspid valve
and the mitral valve in the
heart. When the right
ventricle of the heart
contracts, the blood pressure
pushes the tricuspid valve
which closes and prevents a
backflow of blood into the
right atrium. The chordae
tendineae prevents the flaps
from being everted into the
right atrium. Similarly, these
cord-like tendons hold in
position other flaps like the
bicuspid or mitral valve.
Chordae tendineae are
approximately 80% collagen,
while the remaining 20% is
made up of elastin and
endothelial cells.

The chordae tendinae are
primarily responsible for the
end-systolic position of the
anterior and posterior
leaflets. Arising from the
papillary muscles, they are
classified according to their
site of insertion between the
free margin and the base of
leaflets (see figure). Marginal
chordae (primary chordae)
are inserted on the free
margin of the leaflets and
function to prevent prolapse
of the margin of the leaflet.
Intermediate chordae
(secondary chordae) insert
on the ventricular surface of
the leaflets and relieve
valvular tissue of excess
tension.

2. Papillary Muscles: The
chordae tendinae are
connected to the ventricle
via the papillary muscles,
mitral valve function is
related to the
ventricle. There are two
papillary muscles; medial
and lateral papillary
muscles. Each papillary
muscle provides chordae to
leaflets. The left circumflex
or right coronary artery
provides the blood supply
to the papillary muscles.

3.Commissures: The
commissures define a distinct
area where the anterior and
posterior leaflets come
together at their insertion
into the annulus. Sometimes
the commissures exist as well
defined leaflet segments and
can be identified using two
anatomic landmarks: the axis
of corresponding papillary
muscles and the commissural
chordae, which have a
specific configuration.

4. Leaflets: The valves has
two to three leaflets. The
anterior leaflet has a semi-
circular shape and attaches
to two fifths of the annular
circumference. There is
continuity between the
anterior leaflet of the
mitral valve and the left
and non-coronary cusp of
the neighboring aortic
valve, referred to as the
aortic-mitral curtain.

BLOOD FLOW THROUGH THE HEART
Un-oxygenated blood
enters the atrium on the
right side of the heart
through the superior and
inferior vena cava. While
the un oxygenated blood is
in the right atrium, the
tricuspid valve is closed to
keep the blood from
flowing down to the
ventricle. The atrium
contracts and the tricuspid
valve opens, forcing the
blood down into the
ventricle. The tricuspid
valve closes again so that
blood can not move back
up into the atrium.

The ventricle contracts.
This forces the un
oxygenated blood through
the pulmonary valve and
into the pulmonary
arteries.
The right pulmonary artery
takes the unoxygenated
blood to the right lung.
The left pulmonary artery
takes the unoxygenated
blood to the left lung.
PULMONARY ARTERIES ARE
THE ONLY ARTERIES THAT
CARRY UN OXYGENEATED
BLOOD IN THE BODY.

In the lungs, the
carbon dioxide in
the blood diffuses
into the alveoli.
The oxygen in the
lungs diffuses
into the blood.
This is called
gas exchange.

Oxygenated
blood from the
right lung returns
to the heart
through the right
pulmonary veins.
Oxygenated
blood from the
left lung returns
to the heart
through the left
pulmonary veins.
THE PULMONARY VEINS
ARE THE ONLY VEINS THAT
CARRY OXY GENATED
BLOOD.

The left atrium contracts.
This forces the oxygenated
blood through the mitral
valve into the right
ventricle.
The mitral valve closes
again. This keeps the
oxygenated blood from
moving back up into the
atrium. Oxygenated blood
is forced into the aorta to
be carried to the rest of the
body.

Oxygenated blood is
carried to all body cells
where oxygen diffuses into
the cells and carbon
dioxide diffuses into the
blood. Blood carrying
carbon dioxide then
returns to the heart.
And the cycle begins again.

Lub
If you listen to your
heartbeat, it makes a
lub dub sound.
The lub (S1) is when blood is
pushed out of the atria into
the ventricle and the dub
(S2) is the reloading of the
heart with more blood ready
to push it out to the body
Dub

CORONARY CIRCULATION/ BLOOD SUPPLY TO THE
HEART
The blood supply to the heart
also called as coronary
circulation. The heart
supplied by two coronary
arteries;
 Right Coronary Artery
 Left Coronary Artery
These arteries originate from
the aorta just above the aortic
valve leaflets. The heart has
large metabolic requirement
approximately 70% to 80% of
the oxygen delivered (other
organs consume, on average,
25%). The diameters of the
coronary arteries may
increase up to the 30th year.

Rt. Coronary Artery:
The right side of the
heart is supplied
by the right
coronary artery,
which progresses
around to the
bottom or inferior
wall of the heart.
The posterior wall
of the heart receive
blood supply by an
additional branch
from the right
coronary artery
called Posterior
Descending Artery
(PDA) The bottom
supply continue
with Right
Marginal Artery
(RMA).

Lt. Coronary Artery:
The left coronary
artery has three
branches. These
are The left
anterior
descending artery
(LAD), which
courses down the
anterior wall of the
heart, The Left
circumflex artery
(LCA), which
circles around to
the lateral left wall
of the heart. The
Left Marginal
Artery (LMA),
which mainly
supply to the
lateral wall of left
ventricle.

VENOUS DRAINAGE
Superficial to the coronary
arteries there are the
coronary veins. Venous blood
from these veins returns to
the heart primarily through
the coronary sinus, which is
located posterior in the right
atrium.

FUNCTION OF THE HEART/ CONDUCTION SYSTEM
The specialized heart cells of the cardiac conduction system
generate and coordinate the transmission of electrical impulses to
the myocardial cells. The result is sequential atrioventricular
contraction, which provides for the most effective flow of blood,
thereby optimizing cardiac output. Three physiologic
characteristics of the cardiac conduction cells account for this
coordination:
 Automaticity: ability to initiate an electrical impulse
 Excitability: ability to respond to an electrical impulse
 Conductivity: ability to transmit an electrical impulse from one cell
to another

The conduction system of heart has four elements;
 Sinoatrial (SA) Node
 Atrioventricular (AV) Node
 Bundle of His
 Purkinje Fibers

 Sinoatrial node (SA Node): The Sinoatrial node (SA
Node) is the impulse-generating (pacemaker) tissue located
in the right atrium of the heart. It is a group of cells
positioned on the wall of the right atrium, near the entrance
of the superior vena cava. These cells are modified cardiac
myocytes. The SA node has a firing rate of 60 to 100 impulses
per minute, but the rate can change in response to the
metabolic demands of the body. The electrical impulses
initiated by the SA node are conducted along the myocardial
cells of the atria via specialized tracts called internodal
pathways. The impulses cause electrical stimulation and
subsequent contraction of the atria. The impulses are then
conducted to the atrioventricular (AV) node.
 The Atrioventricular (AV) node: located in the right atrial
wall near the tricuspid valve) consists of another group of
specialized muscle cells similar to those of the SA node.

The AV node coordinates the incoming electrical impulses
from the atria and, after a slight delay (allowing the atria time
to contract and complete ventricular filling), relays the
impulse to the ventricles. This impulse is then conducted
through a bundle of specialized conduction cells (bundle of
His) that travel in the septum separating the left and right
ventricles.
 The bundle of His: divides into the right bundle branch
(conducting impulses to the right ventricle) and the left
bundle branch (conducting impulses to the left ventricle). To
transmit impulses to the largest chamber of the heart, the
left bundle branch bifurcates into the left anterior and left
posterior bundle branches. Impulses travel through the
bundle branches to reach the terminal point in the
conduction system, called the Purkinje fibers. This is the
point at which the myocardial cells are stimulated, causing
ventricular contraction.

PHYSIOLOGY OF CONDUCTION SYSTEM
Cardiac electrical activity is the
result of the movement of
ions (charged particles such
as sodium, potassium, and
calcium) across the cell
membrane. The electrical
changes recorded within a
single cell result in what is
known as the cardiac action
potential.
The normal electrical
conduction of the heart
allowed by electrical
movements to be transmitted
from the SA Node through
both atria and forward to the
AV Node. Normal physiology
allows further electrical
changes from the AV node to
the Ventricle. Both the SA
and AV nodes stimulate the
Myocardium. Time ordered
stimulation of the
myocardium allows efficient
contraction of all four
chambers of the heart.

A myocardial cell has a
negative membrane potential
when at rest. Stimulation
induces the opening of
voltage-gated ion channels
and cations into the cell. The
positively charged ions
entering the cell cause the
depolarization characteristic
of an action potential. After
depolarization, causes
repolarization to the resting
state.
Signals arising in the SA node
stimulate the atria to
contract. In parallel, action
potentials travel to the AV
node. After a delay, the
stimulus is conducted
through the bundle of His to
the bundle branches and
then to the purkinje fibers
and to the ventricular
myocardium.

Cardiovascular system ppt

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