THE HEART

The heart is the most important

muscle in the body.
The heart is about the same size as your
fist
 STRUCTURE OF THE HEART
The heart can be found at the center of the chest,
underneath the sternum in a thoracic compartment.
It is made up of four chambers and several valves
that regulate the normal flow of blood within the
body.
⦿ Two chambers called atria are located in the
upper portion of the heart and receive
oxygen-free blood. The valves that separate these
chambers are called atrioventricular valves which
is composed of the tricuspid valve on the left and
the mitral valve on the right.
⦿ On the other hand, ventricles are chambers
found on the lower portion of the heart; they
pump oxygen-enriched blood into all organs
of the body, reaching even the smallest cells.
Similar to the atria, the ventricular chambers
are also separated by valves.
Collectively-termed as semilunar valves,
these are comprised of the pulmonary and
aortic valve.
⦿ The septum is a thick wall of muscle that
separates the two sets of chambers. It
separates the left and rights sides of the
heart.
⦿
⦿ The heart also has a wall that is composed of
three layers:
1. the outer layer epicardium (thin layer),
2. the middle layer myocardium (thick layer),
3. the innermost layer endocardium (thin
layer).
The myocardium is think because it is made up
of cardiac muscle fibers.
⦿ The structure of the heart is made more
complex because of the mechanisms that
allow blood to be distributed throughout the
body and to return into the heart.
Facilitating this continuous process are two
types of blood vessels: veins and arteries
⦿ The vessels that bring oxygen-free blood
back into the heart are called veins; those
that bring oxygen-rich blood away from the
heart and to other body parts are
called arteries. Functioning in the left
ventricle, the largest artery is called aorta.
The aorta is considered a main artery in the
body. It further splits into two smaller
arteries called common iliac arteries.
TWO PATHWAYS COME FROM THE
:HEART

⦿ The pulmonary circulation is a short loop

from the heart to the lungs and back again.

⦿ The systemic circulation carries blood from

the heart to all the other parts of the body
and back again.
:IN PULMONARY CIRCULATION
⦿ The pulmonary artery is a big artery that
comes from the heart. It splits into two main
branches, and brings blood from the heart to
the lungs. At the lungs, the blood picks up
oxygen and drops off carbon dioxide. The
blood then returns to the heart through the
pulmonary veins.
:IN SYSTEMIC CIRCULATION
⦿ Next, blood that returns to the heart has
picked up lots of oxygen from the lungs. So it
can now go out to the body. The aorta is a
big artery that leaves the heart carrying this
oxygenated blood. Branches off of the aorta
send blood to the muscles of the heart itself,
as well as all other parts of the body. Like a
tree, the branches gets smaller and smaller
as they get farther from the aorta.
HEART VALVES
⦿ The valves of the human heart can be
grouped in two sets:[6]
⦿ Two atrioventricular (AV) valves to
prevent backflow of blood from the
ventricles into the atria
◼ Tricuspid valve, located between the right
atrium and right ventricle
◼ Bicuspid or mitral valve, located between
the left atrium and left ventricle
⦿ Two semilunar valves to prevent the
backflow of blood into the ventricle
◼ Pulmonary semilunar valve, located at the
opening between the right ventricle and
the pulmonary trunk
◼ Aortic semilunar valve, located at the
opening between the left ventricle and the
aorta
 FUNCTION OF THE HEART

⦿ The heart is the main organ in the circulatory

system, the structure primarily responsible for
delivering the circulation of blood and
transportation of nutrients in all parts of the body.
This continuous task uplifts the role of the heart as
a vital organ whose normal operation is constantly
required.
CARDIAC CYCLE
⦿ The heart’s blood-pumping cycle,
called cardiac cycle, ensures that blood is
distributed throughout the body. The oxygen
distribution process begins when oxygen-free
blood enters into the heart through the right
atrium, goes into the right ventricle, enters the
lungs for oxygen refill and release of carbon
dioxide, and transfers into the left chambers,
ready for redistribution. About 5.6 liters of
blood circulate the body and three cardiac
cycles are completed per minute.
⦿ The heart gets messages from the body that tell
it when to pump more or less blood depending
on a person's needs. For example, when you're
sleeping, it pumps just enough to provide for the
lower amounts of oxygen needed by your body at
rest. But when you're exercising, the heart
pumps faster so that your muscles get more
oxygen and can work harder.
⦿ How the heart beats is controlled by a
system of electrical signals in the heart.
The sinus (or sinoatrial) node is a small area
of tissue in the wall of the right atrium. It
sends out an electrical signal to start the
contracting (pumping) of the heart muscle.
This node is called the pacemaker of the
heart because it sets the rate of the
heartbeat and causes the rest of the heart to
contract in its rhythm.
⦿ These electrical impulses make the atria
contract first. Then the impulses travel down
to the atrioventricular (or AV) node, which
acts as a kind of relay station. From here,
the electrical signal travels through the right
and left ventricles, making them contract.

⦿
⦿ The systole is a short period that occurs when the
tricuspid and mitral valves close;

⦿ the diastole is a relatively longer period when the

aortic and pulmonary valves close.

The systole-diastole relationship is the reference in

measuring blood pressure. Other ways of physically
determining the regular functioning of the heart is
through examining the pulse rate (beats per minute). A
normal heart rate of an adult is at 72 beats per minute,
while children normally yield higher heart rates.
THE CARDIAC CYCLE

SYSTOLE : contraction
DIASTOLE : relaxation

ATRIAL DIASTOLE
* begins when both atria and ventricles are relaxed
* blood enters atria
* atrio-ventricular valves are closed
* as atria fill with blood, the pressure rises until it is
greater than that in the ventricles, and the valves are
pushed open
⦿ ATRIAL SYSTOLE
* when atrial diastole ends, the atria contract,
pumping blood into the ventricles
⦿ VENTRICULAR SYSTOLE
* the ventricles then contract, causing a rise in
pressure
* the atrio-ventricular valves close - the first
heart sound
⦿ *the pressure forces open the semi-lunar
valves, and the blood flows out
 ⦿ VENTRICULAR DIASTOLE
⦿ *high pressure in the aorta and pulmonary
artery forces blood back towards the
ventricles, and this closes the semi-lunar
valves : the second heart sound

NB the pulse is caused by ventricular

systole, and the elastic recoil of the
arteries
 HEART SOUNDS
⦿ Heart sounds are sounds produced by the
mechanical activities of the heart during each
cardiac cycle. They are due to movements of
Blood flow through the chambers of the heart
⦿ Some of the common mechanisms by which
heart sounds are generated include
⦿ (1) opening or closing of the heart valves
⦿ (2) flow of blood through the valve orifice
⦿ (3) flow of blood into the ventricular chambers
⦿ (4) rubbing of cardiac surfaces.
⦿ A healthy heart makes a “lub-dub”
sound, which comes from the valves
shutting inside the heart.
⦿ The “Lub” sound happens when the
blood hits valves between the atria
and ventricles.
⦿ The “Dub” sound happens when the
blood hits the aortic and pulmonic
valves the close up as the heart
relaxes to fill the blood for the next
beat.
⦿ There are four heart sounds produced during
each cardiac cycle.
⦿ First & second heart sounds are more
prominent, appear as “LUB & DUB” these
sounds are heard by stethoscope.
⦿ Third heart sound is mild it cannot be heard
by stethoscope in normal conditions, but can
be heard by microphone.
⦿ Fourth heart sound is an inaudible, become
audible in pathological conditions only by
phonocardiogram.