Circulatory System in Human Beings - Transportation in Animals and Plants - CBSE Class 7 Science Video Lecture

the heart is a vital organ of the body
it works as a pump and pushes the blood
into a network of tubes the human heart
is conical in shape with the apex facing
downwards and broad-base upwards it is
situated in the thoracic cavity between
the lungs and above the diaphragm it is
oriented slightly towards the left the
heart is protected by the ribcage on all
sides and by the vertebral column on the
backside the size of human heart is
similar to the sized
of a closed fist
if we observe the cross-section of the
human heart internally it shows four
chambers the upper two chambers are
called
right atrium and left atrium and the
lower two chambers are called the right
ventricle and the left ventricle atria
are thin-walled chambers whereas the
ventricles are thick-walled chambers the
atria are separated by a thin muscular
partition the ventricles are separated
by a thick muscular partition now let us
study the circulation of blood that
occurs inside the heart the right atrium
receives deoxygenated blood from
different parts of the body through vena
cava this blood is pumped into the right
ventricle the opening between the right
atrium and the right ventricle is
guarded by a valve the valve separates
these two chambers thereby avoiding
mixing of blood the valve also allows
blood to flow only in one direction from
the upper part of the right ventricle
the pulmonary artery arises this
pulmonary artery carries deoxygenated
blood to the lungs the left atrium has
four openings of pulmonary veins the
oxygenated blood from the lungs is
brought into the left atrium through the
pulmonary veins this blood is pumped
into the left ventricle through the
valve present between the left atrium
and the left ventricle the main artery
or the aorta arises from the upper inner
part of the left ventricle this main
artery or Herto carries oxygenated blood
which is distributed to different body
organs
heartbeat the process in which blood is
distributed to different body parts and
is again collected and transported back
to the heart is described as blood
circulation the heart is a pumping organ
it undergoes rhythmic contraction and
relaxation
the rhythmic contraction and relaxation
of heart together constitute a single
heartbeat human beings have an average
of 72 heart beats per minute while at
rest
the number of heartbeats increases
during or after any physical exercise or
when a person becomes excited heartbeats
can easily be heard through an
instrument called status cope every time
the heart beats blood is forced into the
arteries the expansion of an artery each
time the blood is forced into it
constitutes a pulse each heartbeat
generates one pulse in the arteries
hence the pulse rate of a person is
equal to the number of heartbeats per
minute our trees are generally situated
deep inside the skin and hence cannot be
used to feel the pulse however at some
places in our body such as the wrist and
the neck arteries are situated close to
the skin surface therefore we can feel
the pulse at these places by pressing
the artery lightly with our fingertips