Human Circulatory System-in detail Video Lecture - NEET

the circulatory system or cardiovascular
system refers to the organs and blood
vessels involved in the transport of
blood throughout the body
it is of two types open and closed
circulatory system is found in
arthropods and mollusks
in these organisms
the heart reaches the open spaces or
body cavities called sinuses through
large blood vessels and bathe all the
organs
whereas opposed circulate
the system is found in annelids and
Chordata
in these organisms
the blood pumped from the heart passes
through the closed blood vessels to
reach the tissues
heart
our circulation
is made of cardiac muscles
it has many chambers
very between animals
for example
fishes have a two chambered heart
comprising one atrium and one ventricle
amphibians and reptiles
exception of crocodiles have a three
chambered heart comprising two atria and
one ventricle
on the other hand
dials birds and mammals have a four
chambered heart comprising two atria and
two ventricles
the blood circulation in these animals
also differs due to the difference in
the number of chambers
for example
fishes exhibit single
circulation
the oxygenated blood
is pumped from the heart to the gills
for oxygenation and the oxygenated blood
directly flows into the tissues
whereas the oxygenated blood collected
from the tissues is returned to the
heart
in this way
is through the heart only once during
circulation and hence this is called
single circulation
frogs and reptiles exhibit incomplete
double circulation
oxygenated blood from the lungs or gills
or skin reaches the left atrium while
deoxygenated blood from body tissues
reaches the right atrium
blood from the left and right atrium is
mixed in the single ventricle
twice and gets me
in the single ventricle during
circulation
and hence this is called incomplete
double circulation
birds and mammals exhibit double
circulation
oxygenated blood from
reaches the left atrium awhile
deoxygenated blood from body tissues
reaches the right atrium
the blood from both the atria is
released into their respective
ventricles thus preventing any mixing
in this way
blood passes
the heart twice during circulation and
hence this is called double circulation
during blood circulation
added to all the tissues through a set
of blood vessels called arteries
tissues reaches the heart through
another set of blood vessels called
veins
other these are large
let's carry oxygenated blood from the
heart and branch out to form small
arterioles that end in capillaries to
reach the tissues these capillaries
collect deoxygenated blood from tissues
and converge to form venules which
finally converge to form the large blood
vessels the veins
however there are two exceptions in
which the artery and vein perform
different functions the pulmonary artery
carries deoxygenated blood from the
heart to the lungs while the pulmonary
vein carries oxygenated blood from the
lungs to the heart
now let's look at the structure of the
human heart in detail
the heart is about the size of a fist
and lies in the thorax between the two
lungs
slightly tilted towards the left lung
it is protected by a double-walled
membranous sac called the pericardium
encloses pericardial fluid
it has four chambers that include two
upper small atria and two lower large
ventricles
thin muscular wall called the
interatrial septum separates the two
atria why the thick interventricular
septum separates the two ventricles
besides
you called the atrioventricular septum
separates the atria from their
respective ventricles
however there are openings between the
chambers of the heart which are guarded
by three types of valves that allow the
flow of blood in one direction
is made of three muscular flaps or cusps
and guards the opening to the right
atrial ventricular septum
the bicuspid
mitral valve is made of two muscular
flaps or cusps and guards the opening to
the left atrial ventricular septum
the semilunar valves guard the opening
between the right ventricle and
pulmonary artery
between the left ventricle and iota
when these valves closed they produce a
loved-up sound heard during a heartbeat
cuspid and bicuspid valves produces the
first sound love
the closure of the semilunar valves
produces the second sound dub
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also
specific regions in the heart consist of
specialized cardiac muscles called nodal
tissues
the first knodel tissue the sinoatrial
node or sin is present in the top right
corner of the right atrium
the hand
tissue
a node or ABN
corner of the right atrium near the
atrioventricular septum
another group of loaded tissues starts
as an atrial ventricular bundle or AV
bundle from the avian and passes through
the atrioventricular septum and then
through the interventricular septum
this finally branches into right and
left bundles in the ventricles to form
minut Purkinje fibers over the
ventricles
all these fibers together form the
bundle of His
here the sand can
to magically generate around 70 to 75
action potentials or electrical impulses
to a minute
this action potential is transmitted to
every other part of the heart through
the AV node and bundle of his to bring
about the rhythmic contraction of the
heart
this is why the average heart beats 72
times per minute
and
the sin is called the pacemaker of the
heart
in some cases
an artificial pacemaker is used in
individuals suffering from heart
problems relating to the sand
potentials or electrical impulses in
place of the natural pacemaker the sin
yes
the transmission of action potential to
different parts of the heart is
essential for blood circulation
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