Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET Derived Question.
If due to some injury the chordae tendinae of the tricuspid
valve of the human heart is partially non - functional, what
will be the immediate effect?
(a) The flow of blood into the aorta will be slowed down.
(b) The ‘pacemaker’ will stop working.
(c) The blood will tend to flow back into the left atrium.
(d) The flow of blood into the pulmonary artery will be
reduced.
Answer: d
If due to injury the chordae tendineae of the tricuspid valves of the human heart is partially non-functional, the flow of blood into the pulmonary artery is reduced due to backflow of blood into the right atrium.
Tricuspid
👉Heart, the mesodermally derived organ, is situated in the thoracic
cavity, in between the two lungs, slightly tilted to the left. It has the size of
a clenched fist. It is protected by a double walled membranous bag,
pericardium, enclosing the pericardial fluid. Our heart has four
chambers, two relatively small upper chambers called atria and two larger
lower chambers called ventricles.
👉A thin, muscular wall called the interatrial
septum separates the right and the left atria, whereas a thick-walled,
the inter-ventricular septum, separates the left and the right ventricles
👉The atrium and the ventricle of the same side are also
separated by a thick fibrous tissue called the atrio-ventricular septum.
👉The opening between
the right atrium and the right ventricle is guarded by a valve formed of
three muscular flaps or cusps, the tricuspid valve, whereas a bicuspid
or mitral valve guards the opening between the left atrium and the left
ventricle.
👉The openings of the right and the left ventricles into the
pulmonary artery and the aorta respectively are provided with the
semilunar valves.
👉How does the heart function? Let us take a look. To begin with, all the
four chambers of heart are in a relaxed state, i.e., they are in joint
diastole. As the tricuspid and bicuspid valves are open, blood from the
pulmonary veins and vena cava flows into the left and the right ventricle
respectively through the left and right atria. The semilunar valves are
closed at this stage. The SAN now generates an action potential which
stimulates both the atria to undergo a simultaneous contraction – the
atrial systole. This increases the flow of blood into the ventricles by about
30 per cent. The action potential is conducted to the ventricular side by
the AVN and AV bundle from where the bundle of His transmits it through
the entire ventricular musculature. This causes the ventricular muscles
to contract, (ventricular systole), the atria undergoes relaxation
(diastole), coinciding with the ventricular systole. Ventricular systole
increases the ventricular pressure causing the closure of tricuspid and
bicuspid valves due to attempted backflow of blood into the atria. As
the ventricular pressure increases further, the semilunar valves guarding
the pulmonary artery (right side) and the aorta (left side) are forced open,
allowing the blood in the ventricles to flow through these vessels into
the circulatory pathways. The ventricles now relax (ventricular diastole)
and the ventricular pressure falls causing the closure of semilunar valves
which prevents the backflow of blood into the ventricles. As the
ventricular pressure declines further, the tricuspid and bicuspid valves
are pushed open by the pressure in the atria exerted by the blood which
was being emptied into them by the veins. The blood now once again
moves freely to the ventricles. The ventricles and atria are now again in
a relaxed (joint diastole) state, as earlier. Soon the SAN generates a new
action potential and the events described above are repeated in that
sequence and the process continues.
👉During each cardiac cycle two prominent sounds are produced which
can be easily heard through a stethoscope. The first heart sound (lub) is
associated with the closure of the tricuspid and bicuspid valves whereas
the second heart sound (dub) is associated with the closure of the
semilunar valves.