6. THE HUMAN HEART
The heart is a muscular organ, which act as a pump.
It is about size of your fist.
It lies the chest cavity between the lungs with its
lower end tilted a bit of the left.
The heart has four chambers- right atrium, left
atrium, right ventricle, and left ventricle.
The heart is divided into two halves by a thick wall.
7. This wall prevent oxygenated blood from mixing
with deoxygenated blood.
Deoxygenated blood carrying carbon dioxide from
all parts of the body enters the right side through two
major veins (superior & inferior vena cava).
The heart pumps in to two arteries, which carry it to
the lungs.
In the lungs, the blood gives up carbon dioxide and
picks up oxygen.
8. The oxygenated blood, blood carrying oxygen then
enters the left side of the heart which pump it in to
the artery.
Branches of this artery carry the oxygenated blood
to the rest of the portions.
9. Automatic Rhythm of Heart
Heart beat is the result from a wave of electrical
potential called the cardiac impulse.
Human heart is myogenic.
The heart beat is originated from a specialized cardiac
muscle fibres called nodal tissue.
The nodal tissue formed of two contraction centres
and a conducting system of fibrils.
The contraction centres include SA node and AV node.
10. HEART BEAT
• The function of heart is to pump blood to various parts
of the body.
This is brought about by the relaxation and
contraction of its chambers.
Contraction of the chambers of the heart is known as
systole and their relaxation is known as diastole.
A contraction and subsequent relaxation constitute a
heartbeat.
11. CARDIAC CYCLE
The relaxation of all the four chambers of the heart is
known as joint diastole.
The sequential events which occur from the beginning
of one heart beat to the beginning of the next is known
as cardiac cycle.
It consists of systole and diastole of both atria and
ventricles.
The duration of cardiac cycle is 0.8 seconds.
The heart beat once in 0.8 seconds.
