1.2 Structure of the Coronary Circulation

Question 1

What does it mean that coronary arteries are “end arteries”?

Answer 1

They supply the myocardium without sufficient overlap or anastomoses; if one is blocked, then the corresponding section of the heart will be starved of oxygen

Question 2

What two sets of coronary arteries are likely to anastomose with one another?

Not shown in textbooks or in Noted Anatomist’s video, but inferred by Ha

Answer 2

• LAD and RPD
• Circumflex branches of RCA and LCA

Question 3

Which coronary artery supplies the AV node? Which supplies the bundle of His?

Answer 3

AV Node: Posterior descending
Bundles of His: Left anterior descending

Question 4

What are the names of the three cusps of the aortic valve?

Answer 4

• Left coronary cusp
• Right coronary cusp
• Non-coronary cusp

Question 5

What are the openings of the coronary arteries within the aortic wall called?

Answer 5

Ostium

Question 6

What structures does the left coronary artery travel between?

Answer 6

• Pulmonary trunk
• Left auricle

Question 7

Left dominant vs right dominant coronary circulation

Answer 7

Left Dominant: Left Circumflex gives rise to posterior interventricular artery
Right Dominant: Right coronary artery gives rise to posterior interventricular artery

Question 8

In what percentage of cases does the AV nodal branch come from the left/right coronary arteries?

Answer 8

Right: 60%
Left: 40%

Question 9

How much of the interventricular septum is supplied by the LAD vs the posterior descending artery?

Answer 9

LAD: 66%
Posterior Descending: 33%

Question 10

Describe the structures supplied by the left coronary artery in a normal, balanced distribution

Answer 10

• 2/3 of IV septum
• AV Bundle
• Left ventricle
• Part of right ventricle
• Left atrium
• SA Node (40%; not normal)

Question 11

What is the branch of the left circumflex artery on the postero-inferior surface of the heart called?

Answer 11

Posterior left ventricular branch

Question 12

Describe the structures supplied by the right coronary artery in a normal, balanced distribution

Answer 12

• Most of the right ventricle
• Right atrium
• Sinoatrial node
• Atrioventricular node (60%)
• 1/3 of interventricular septum

Question 13

Are the coronary arteries perfused during systole at all?

Answer 13

Yes; just less than during diastole

Question 14

Are the right coronary arteries perfused during systole at all?

Answer 14

Yes; just less than during diastole

Question 15

True or false: there is a valve between the great cardiac vein and coronary sinus

Answer 15

True

Question 16

What valve connects the coronary sinus to the right atrium?

Answer 16

Thebesian valve

Question 17

Is the thebesian valve really a valve?

Answer 17

No; it is merely a layer of membrane that can direct blood flow.

Question 18

Describe the three sources of coronary venous drainage directly into the RA, and their corresponding percentages

Answer 18

Coronary sinus: 65%
Directly into RA via anterior cardiac veins: ~25%
Thebesian veins: 10%

Question 19

List three neuro-humoral factors that contribute to coronary autoregulation

Answer 19

• Acetylcholine
• Noradrenaline
• Adrenaline

Question 20

List four endothelial factors that contribute to coronary autoregulation

Answer 20

• NO
• PGI2
• Endothelium Derived Hyperpolarisation Factors
• Endothelin

Question 21

This three metabolic factors that contribute to coronary autoregulation

Answer 21

• PO2 and PCO2
• [H+] and [K+]
• Adenosine

Question 22

List three endocrine and paracrine factors that influence coronary autoregulation

Answer 22

• Bradykinin
• Histamine
• Angiotensin II

Question 23

Do sensory neurons travel from the heart to the brain? Why?

Answer 23

Yes; to ensure that perfusion and blood pressure remains in normal, healthy ranges

Question 24

What structures of the heart does the sympathetic nervous system innervate?

Answer 24

• SA Node
• AV Node
• Coronary Arteries
• Cardiomyocytes

Question 25

What structures of the heart does the parasympathetic nervous system innervate?

Answer 25

• SA Node
• AV Node
• Coronary Arteries

Question 26

What is the effect of parasympathetic/sympathetic innervation on coronary arteries

Answer 26

Sympathetic: Constricts (relocates more blood to ventricles, where there is no constriction)
Parasympathetic: Dilates