Lectures

Coronary Circulation – Heart (Cor)

by Craig Canby, PhD
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    00:00 does not issue a coronary artery. So it?s a non-coronary-related cusp. So that leads us then to an understanding of the coronary circulation.

    00:09 The heart, as you might imagine, has an intense metabolic need for nutrients and for oxygen.

    00:19 And there are two arteries that will help supply the heart with arterial blood. At rest, about 225 ml per minute of blood is being delivered to the heart through the right coronary artery and through the left coronary artery. Again, coronary means ?crown? and these arteries will form a crown around the heart itself and then issue numerous branches.

    00:47 If we take a look in this view, we can see our right coronary artery travelling down within the coronary sulcus or atrioventricular sulcus. It will wrap around to the posterior diaphragmatic area of the heart and still will travel within the coronary sulcus. And we can see some branches issuing from the right coronary here in this view. And then along the right margin of the heart we see a marginal artery issuing from the right coronary.

    01:25 The left coronary artery we see here it?s going to issue from the aorta right above the left coronary semilunar cusp. It?s travelling posterior to the pulmonary trunk and underneath the left auricle. So the left auricle bridges over the left coronary artery. The left coronary artery at first is a very short segment. And then it?s going to issue its two branches.

    01:55 The one that travels in the anterior interventricular sulcus is referred to as the anterior interventricular artery. And then the other one that we see here is going around within the coronary sulcus but it?s wrapping around the left side of the heart travelling within the coronary sulcus.

    02:20 And as it wraps around, it?s when it?s called the circumflex artery.

    02:31 If we take a look at the coronary arteries, there is a dominance or dominant pattern that can be determined. And if we take a look here, we have our right coronary artery. And, if we follow our right coronary within the coronary sulcus and see it wrap around the right side of the heart as we do here, we will see that the right coronary artery will dive down into and travel within the posterior interventricular sulcus. When the right coronary artery gives rise to the posterior interventricular artery that travels in this posterior interventricular sulcus, this is called a right dominant pattern. The majority of individuals have a right dominant system. The percentage will vary from one study to another. So it might be 70%, 80% or maybe a little bit higher than that in frequency.

    03:34 Here we?re looking at the opposite dominant pattern. And if we take a look at what?s going on here, we will see our left coronary artery. We see the anterior interventricular artery travelling in the anterior interventricular sulcus, which is normal. Another name for our anterior interventricular artery is our left anterior descending artery, or the acronym LAD. And LAD is commonly used in the medical profession.

    04:09 The circumflex artery is issuing right at this point. And if we follow it around the left margin of the heart to the diaphragmatic view ? posterior view, we see it also travelling in the coronary sulcus. And if we follow it distally, we see it dives down into the posterior interventricular sulcus thereby continuing as the posterior interventricular artery.

    04:36 And when it?s the left, in this case the circumflex that gives rise to the posterior interventricular artery, you?ll want to call this a left dominant pattern. This is the second most frequent pattern that we?ll see. However, it is usually somewhere around 15, 16 maybe 17% in frequency.

    04:59 The last pattern that can be seen as a variant is a balanced pattern. In a balanced pattern, what happens is we end up with two posterior interventricular arteries, one coming from the right coronary artery and then, if we can move this one over here more in line here and running parallel to the one coming from the right we have two more clearly defined, discernible posterior interventricular arteries. That is a balanced pattern. And out of the three, this one is the least frequent pattern that we?ll see.

    05:43 Here we have a superior view of the coronary arteries. Here?s the aorta cut in cross section. Here is your right coronary cusp or right cusp. And here you can see the ostium leading into the right coronary artery. The right coronary artery in a dominant pattern is going to supply primarily the right side of the heart: right ventricle, right atrium.

    06:12 Also it will supply important structures at the conduction pathway: the SA node. And we can see the artery right here leading to the SA node. And it?ll also issue posteriorly here most commonly an artery to the atrioventricular node.

    06:32 It also helps supply the interventricular septum.

    06:36 Here is the left coronary artery. The ostium is right here, right above the left coronary cusp. And again very short. Here you can see it continuing as the anterior interventricular artery or the LAD. This is the one that?s most frequently blocked leading to a myocardial infarction. And it can lead to death. Hence it?s also referred to as the widow maker.

    07:04 And then here?s your circumflex wrapping around as we see here.

    07:12 Here?s your posterior interventricular artery. And I?ll give you a moment to think about it.

    07:17 Which coronary artery is giving rise to the posterior interventricular artery? And the answer is the right one coming around, diving down into the posterior interventricular sulcus. So this is a right dominant pattern. The left in this case is supplying mainly the left ventricle, left atrium, interventricular septum.

    07:49 Like any other organ that?s receiving a blood supply, the heart also has to have structures in place that will help drain the organ of venous blood.

    08:01 So we do have a system of veins to do that.

    08:06 The main veins to keep in mind here as a learner will be the great cardiac vein, the middle cardiac vein and the anterior cardiac veins. Here in this view ? the sternocostal anterior view ? we can see the first vein and the last bulleted veins. So travelling here in the anterior interventricular sulcus with the anterior ventricular artery or the LAD is its accompanying vein. And blood is flowing upwards here in this system. This is called the great cardiac vein and it?s going to dive into the coronary sulcus, wrap around the left margin of the heart and empty into a structure that we call the coronary sinus, a co-acting system.

    08:52 We can also see here ? on the right ventricular side ? we see in this case three anterior cardiac veins. They?re draining the right ventricle primarily of venous blood and they empty directly into the right atrium. So they?re very small ostea or openings here into the right atrium.

    09:18 The next slide will help us to understand some of the additional veins and also see what we saw on the anterior view wrapping around here to the posterior view. And so what we?ll want to focus on here, for a reference, is the great cardiac vein coming up and around to empty into the coronary sinus.

    09:46 The coronary sinus will receive most of the venous blood flow being drained from the heart.

    09:52 A separate opening, large opening into the right atrium that we saw in an earlier slide when we looked at the internal anatomy of the right atrium. We also have here, accompanying the posterior interventricular artery, we have its vein. This is called the middle cardiac vein. It drains blood also into the coronary sinus and thence into the right atrium.

    10:16 We also have some smaller veins that will empty into the coronary sinus. So the coronary sinus drains most of the heart of venous blood. The anterior cardiac veins are going to drain primarily the right ventricle. And the last system of veins that we have we cannot see in this view. They run deep within the muscle tissue itself and drain into the cardiac chambers.

    10:47 And these are the venae cordis minimae.


    About the Lecture

    The lecture Coronary Circulation – Heart (Cor) by Craig Canby, PhD is from the course Thoracic Viscera.


    Included Quiz Questions

    1. Left and right.
    2. Anterior and posterior.
    3. Superficial and deep.
    4. Medial and lateral.
    5. Superior and inferior.
    1. 2.
    2. 1.
    3. 4.
    4. 6.
    5. 8.
    1. Right dominant pattern.
    2. Left dominant pattern.
    3. Ventricular dominant pattern.
    4. Developmental defect.
    5. Genetic disorder.
    1. 15-17%.
    2. 10-12%.
    3. 8-10%.
    4. 18-20%.
    5. 20-25%.
    1. Anterior coronary veins.
    2. Great coronary vein.
    3. Middle coronary vein.
    4. Small coronary vein.
    5. Left marginal vein.

    Author of lecture Coronary Circulation – Heart (Cor)

     Craig Canby, PhD

    Craig Canby, PhD


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