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eval_testing_mns

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anterior end of the right side of the heart is superior venacava (precaval
vein), which collects blood from anterior parts (head and neck) of the
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body.
The vein which brings blood from posterior parts of the the body (hands,
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legs etc.) is inferior venacava (postcaval vein).
The two atria and the two ventricles are separated from each other by
muscular partitions called septa. The openings between atria and ventricles
are guarded by valves.
The valve present on the Right Auriculo-ventricular septum between
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Right atrium and Right Ventricle is referred to as “Tricuspid Valve”. The valve present on
the left Auriculo-ventricular septum between left atrium and left ventricle is referred as
Bicuscid valve or Mitral valve. A major blood vessel that originate from right ventricle is
Pulmonary aorta. The valves present at the region of Pulmonary aorta are called
“Pulmonary valves”. A major blood vessel originates from left ventrical is systemic aorta.
The valves present at the region of systemic aorta are called Systemic valves.
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Free distribution by T.S. Government 2019-20 53
In the right atrium we can observe the openings of superior and inferior
venacava. In the left atrium, we can observe the openings of pulmonary
veins, that bring blood from lungs.
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From the upper part of the left ventricle, a thick blood vessel called
aorta arises. It supplies oxygenated blood to the body parts. From the upper
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part of the right ventricle pulmonary artery arises that supplies de-
oxygenated blood to the lungs. After careful examination we can observe
valves in the pulmonary artery and aorta as well.
The blood vessels and circulation
Let us study how we came to know about the structure and functions
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of the blood vessels.
It was not until 16th century that we really came to know how our blood
vessels functioned. In 1574, an Italian doctor, Girolamo Fabrici, was
studying the veins in the leg. He noticed that they had small valves in them.
If the blood moved in one direction, the valves folded towards the walls of
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the vessel, so that the blood could pass without trouble. If the blood moved
in the opposite direction, the valves closed.
This meant they are one-way valves. The valves permitted the blood to
move even when a person is standing upright. But not move downward.
When a person moves his legs, or just tightens his leg muscles, those
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muscles squeeze the veins and force the blood in those veins to move
upward against the pull of gravity (because that’s the only way to go). If a
person keeps his leg muscles relaxed, the blood isn’t moving much, but at
least it isn’t being pulled down by gravity. The valves won’t allow that.
Everyone thought that the blood leaving the left ventricle always moved
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away from the heart for which Fabrici paid no attention. He missed the
importance of his own discovery. But then, William Harvey (1578-1657),
an Englishman who, after he became a doctor, went to Italy for further
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education and studied under Fabrici.
Harvey dissected the hearts of dead people and studied the valves
between each atrium and its ventricle. He noticed that they were one-
way valves. They allowed the blood to flow from the atrium to the
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ventricle without any hinderance.
When the heart contracted, however, no blood in the ventricle
could flow back into the atrium. Instead, all the blood was pushed out
into the arteries.
fig-6: William Harvey began thinking about the valves his teacher, Fabrici, had
Harvey discovered in the leg veins. They were one-way, and they forced the
blood to move toward the heart.