hi let's talk about the coronary arteries in this video we'll discuss the arterial supply
of the heart by diagramming the pathways and branches of the left and right coronary arteries
so the coronary arteries begin their journey and the root of the aorta that's the portion of
the ascending aorta that is most proximal to the heart there is a right coronary sinus of valsalva
and a left coronary sinus of valsalva that feed the right and left coronary arteries
respectively notice that these arteries are traveling through the coronary sulcus coronary
sulcus gets its name from the coronal plane well the largely coronal plane that it occupies
coronary doesn't mean heart coronal means crown and so the arteries are named for the sulcus
that largely contains them also recall that the aortic valve only closes
during diastole and so the rca and the lca only fill with blood during diastole
let's start our tour with the right coronary artery hereby referred to as the rca
so that is originating in the right coronary sinus it leaves the ascending aorta and enters
into the coronary sulcus and its first branch is the sinoatrial nodal branch or the sa nodal branch
this is supplying the sa node of the heart as well as portions of the wall of the right atrium
this is a branch of the rca in about six out of every ten individuals in the remaining four out of
ten individuals it's a branch of the left coronary artery the rca then travels down in the coronary
sulcus down towards where that right border meets the inferior border and along the way it will
give off branches to serve the right ventricle and one of these is a named branch called the
right marginal branch the right marginal branch is going to hug the inferior border of the heart
the rca then wraps around here let's pick this up here wraps around within the coronary sulcus
and goes out typically to a region known as the crux of the heart this is going to be important
later on that crux region is typically the area where two other branches arise there's the av
nodal branch or the atrioventricular nodal branch and then the posterior interventricular branch the
posterior interventricular branch is communicated along the posterior interventricular sulcus
and that branch is going to have septal branches that supply the interventricular septum
now in almost 70 percent of individuals these branches are supplied exclusively by the rca
in the remaining amount of individuals
they are either supplied by both the rca and the lca a condition known as codominance
so rca and lca serving the crux is codominance
or exclusively by the lca in a minority of cases and that's a condition known as
left dominance so if it's by the rca it's right dom by both codominance and by
the lca left dominance and we'll we'll see this further so let's look at these branches
categorically here's the origin of the rca there's the sa nodal branch there's the coronary
right coronary artery descending down in that coronary sulcus at the bottom there we can see
the right marginal branch we can get a better look at it from this
anterolateral view you can see more of the the right surface and border of the heart and there
is that right marginal branch going out along the inferior border so the rca then wraps around
so it's coming around there this is an interesting orientation my apologies for it and we can see the
rca continuing to serve the crux of the heart where we have the posterior interventricular
branch and the av nodal branch so this is an example of a right dominant heart here
the septal branches are drilling deep into that myocardium and into the interventricular septum
so let's take a look at the lca the lca arises from the left coronary sinus it travels behind the
pulmonary trunk into that coronary sulcus and it branches into the anterior interventricular branch
also known as the left anterior descending or the lad that will host septal branches supplying
the interventricular septum the other branch is the circumflex branch the circumflex branch
stays within the coronary sulcus and wraps around to the posterior aspect of the heart sometimes
getting to that crux of the heart but most of the time not getting there one branch off of the
circumflex is the left marginal branch that hugs the left border of the heart curiously enough out
of all of the branches of the coronary arteries the left marginal is the only one designated as
an artery and not a branch but let's look at these on the kind of varic photos there's the origin of
the lca we can see that we have a very early split for the anterior interventricular branch
then we have the circumflex branch and that wraps around there is our left marginal artery you can
probably see it better here in fact we can there's the anterior iv branch here's the circumflex
coming down and then there is the left marginal artery so as i've said before heart dominance
is determined by the coronary artery supply to the crux of the heart whichever arteries get
to the crux which is where the av nodal branch and posterior interventricular branches arise
are the arteries that are going to determine dominance most hearts are right dominant hearts
so 67 of them and then there is no clear consensus in the literature for exact percentages that
vary between codominance and left dominance but codominance where both the rca and lca
supply the crux is the next most frequent condition and the least frequent condition
is left dominance where the lca supplies the crux of the heart let's for a moment imagine why left
dominant hearts are at a selective disadvantage with a left dominant heart we would have the
anterior interventricular branch as well as the posterior interventricular branch supplying the
interventricular septum by the lca so that's a lot of real estate that's quite a bit of the walls of
the ventricle that would be supplied exclusively by the left coronary artery if there was any
occlusion of the lca it would be absolutely catastrophic not just for the walls
of the ventricles but also for the cardiac conduction system so the uh the bundle of
his and the bundle branches that are conducted down along through that interventricular septum
so we've discussed the left and right coronary arteries and their branches and what they supply
and how they contribute to heart dominance this is your summary slide thank you for your time