So moving on to the left ventricle just a bit about its position so remember the
the heart is
angled in the mediastinum so the right ventricle forms
most of the anterior surface
and the left ventricle which is this part of the heart
actually sits a bit
posterior to the right ventricle
and it sits anterior to the left atrium
so that's just a bit about the position
of the left ventricle
So I've just dissected away the wall of the left ventricle and we're looking inside at
some of the structures
so when blood enters from the left atrium into the left ventricle it passes through
the left
atrioventricular orifice
so this orifice forms this
fibrous ring
on which you've got the mitral valve attaching
so the mitral valve is also sometimes called the bicuspid valve because it has two
cusps
you've got anterior cusp which is larger
and you've got a posterior cusp at the back which is a little bit smaller
so you've got these two cusps. So anteriorly you've got the anterior cusps
and you've got the
smaller posterior cusps at the back
and just like in the right ventricle it's attached to a papillary muscle by
these
chordae tendinae, so these
cords which you can see here and I'm just highlighting them in yellow and
you've got the
the papillary muscle here anchoring it to the
ventricular wall
so the reason it's called a mitral valve is because apparently it resembles
a bishops mitre
so i guess you could say that you've got these two cusps, so you've got an anterior cusp
and you've got a posterior cusp
so that may help you remember
the sort of shape of the mitral valve, so it was supposed to resemble a
bishops mitre
and this view here shows a horizontal section, wo we are looking at it from
the top, and you can see the two valves here
of the bicuspid valve, or mitral valve
so they open IN
towards the ventricle
so just like the right ventricle you've got
trabeculae carneae
in the left ventricle
so they're a little bit different in that they're a little bit
finer and smaller
but the general appearance is the same where you have the three different
types of trabeculae carneae
so you've got the papillary muscles
which are not tethered at one, so one is
anchored to the ventricular wall and the other
provides attachment to the chordaea tendineae
and then you've got the other two types of trabeculae carneae which are tethered
along their entire length and which
are tethered at either end and free in the middle. So check out the
video on the right ventricle for a bit more
details there
So I've removed the ventricle wall here and
just kind of
drawn a vague outline for the wall here, so you can see the two papillary
muscles, so you've got an anterior
papillary muscle
and you've got a posterior papillary muscle
so the function of the papillary muscles is the same as the right ventricle
so together with the chordae tendinaea they holds the mitral valves in place, so you've
got the mitral valves held
so that they're pointing in towards the left ventricle
If you didn't have these structures tethering the valve in place
when the left ventricle contracts, and blood is forced backwards against
the valves
without being anchored in place like this
the valves would
invert, so they'd be
reflected back into the atrium and then
blood would be
allowed to flow back into the left atrium which wouldn't be good
So just rotating the model around again
Just to mention the left ventricular wall
is very thick, it's much thicker than the right ventricular wall
and the reason for this is that it has to pump blood
to the entire body into the head
So it's pumping against a much higher resistance then the right ventricle
so the right ventricle just pumps blood to the lungs, but the left
ventricle need a thicker
myocardium so that can pump blood
to the whole body so
when blood is pumped out of the left ventricle, it ascends through this outflow tract, this
left ventricular outflow tract
which is known as the aortic vestibule
so this outflow tract is continuous with the ascending aorta above
and if i rotate the model around, you can see
the relationship of the aortic vestibule to the right ventricular outflow tract
so the right ventricular outflow tract here, sits anteriorly to the
left ventricular outflow tract
So I've just removed some structures from the model so you can visualize the
aortic valve
so up here we've got the ascending aorta and you'll notice that there's two
vessels coming off
here these are the coronary arteries so you've got the left and the right
coronary artery coming off right at the beginning of the ascending aorta
so if I just remove
this for a moment you can see that valve - the aortic valve
so I've just isolated that valve here and you can see that it's similar in
structure to the pulmonary valve
so you've got these three semi luna cusps
and you've got a right
and left
and posterior cusp
so what's important to talk about is the relationship of this valve
to the coronary arteries
immediately about the aortic valve
on the right and left you've got the right coronary artery
and the left coronary artery
so these arteries open in the sinuses off the right and the left
semi lunar cusps
to coming again to this horizontal section of the heart you can see the
aortic valve here
with it's
three cusps
so you've got these
right, left and posterior cusps and you can see
the opening of the
left coronary artery into the left
cusp and you can see the opening of the right coronary artery into the right cusp
so this diagram here shows nicely
the configuration of the aortic valve
so what we're looking at is, we've
cut open
a section of the aorta and the outflow tract and we've opened it out flat, so
we've got the three cusps in a row here
so you've got the left cusp
and the right cusp
and just like the pulmonary valve you've got this thickening
called the nodule
and you've got to this thin part which is called the lunulus
and then you've got the aortic sinus which is this area between
the wall of the vessel
and the cusp
so you've got this area called the aortic sinus
and in the
right and the left cusp, you've got the openings, the origins of the right and
left coronary arteries
opening into this sinus
so this is important to know about, because during systole, during
ventricular contraction you get blood
rushing out through the ventricles
and out through the aortic valves into the ascending aorta
and then during diastole, when the ventricles relax
you get blood flowing back
down the ascending aorta
and you get pooling of the blood in the sinuses
so during diastole, the sinuses fill with blood and it then fills
the coronary arteries with blood
so this is important to know, and essentially
you get most of the coronary blood flow during
diastole
because of this relationship of the origins of the coronary arteries
to the aortic sinuses
so that's the left side of the heart, and that completes my series on the
for chambers of the heart and some of the features that you need to know about