Middle mediastinum - heart - conducting system and blood supply (Dave's notes)

Question 1

List the components of the conducting system of the heart in sequence

Answer 1

SA node ->atrial cardiac muscle fibres -> AV node -> AV bundle -> R and L -> subendothelial purkinje fibres

Question 2

Describe the SA node. What does it contain?

Answer 2

The SA node is made of specialised muscle fibres. Crescent shaped, 1-2cmx5mm thick. Contains central stellate cells.

Question 3

What differentiates the central stellate cells of the SA node from the rest of the myocardium?

Answer 3

They have fewer myofilaments than ordinary cardiac muscle.

Question 4

Where is the AV node located?

Answer 4

Buried in the muscle of the interatrial septum.

Question 5

What path does cardiac lymph follow?

Answer 5

Cardiac lymph follows the arteries.

Question 6

Where is cardiac innervation from?

Answer 6

The cardiac plexus. Also NB baroreceptors

Question 7

What two main arteries comprise the blood supply to the myocardium?

Answer 7

R) coronary artery and the L) coronary artery

Question 8

Describe the path of the right coronary artery

Answer 8

Passes between the auricle, vertically downwards and then posteriorly

Question 9

List the branches of the right coronary artery

Answer 9

Conus artery
SA nodal artery
Right marginal artery
AV nodal artery
Posterior interventricular artery

Question 10

Describe the path of the left coronary artery

Answer 10

Arises behind the pulmonary trunk, dividing into the circumflex (continuation of) and anterior interventricular (LAD)

Question 11

What is the conus artery a branch of? What is its path?

Answer 11

The RCA. Passes upwards and medial

Question 12

What is the SA nodal artery a branch of.

Answer 12

The RCA in 60% of cases, the LCA in 40% of cases

Question 13

What is the right marginal artery a branch of?

Answer 13

The inferior margin of the RCA

Question 14

What is the AV nodal artery a branch of? Where is it found?

Answer 14

The RCA. Found lying posteriorly.

Question 15

What is the posterior interventricular artery a branch of? What is its course?

Answer 15

The RCA. Passes along the interventricular groove to the apex.

Question 16

List the branches of the left coronary artery

Answer 16

SA nodal
Circumflex
Anterior IV (LAD)
Left conus branch

Question 17

What is the circumflex artery a branch of? What is its course?

Answer 17

The LCA. Passes down the back of the heart, giving off various branches.

Question 18

What is the anterior IV (LAD) a branch of? What is its course?

Answer 18

Runs down in the interventricular groove, to anastomose with the posterior interventricular branch

Question 19

Describe the left conus branch. What is its clinical significance?

Answer 19

The left conus branch comes off the LCA near its origin and runs onto the upper part of the right ventricle, providing a potential anastomosis with the conus branch of the right coronary.

Question 20

What are the diagonal and obtuse marginal branches of?

Answer 20

The LCA - these are several large ventricular branches given off, named diagonal and obtuse by radiologists.

Question 21

What is notable about cardiac blood supply?

Answer 21

There is considerable variation in the way major branches end and anastomose, in particular the interventricular vessels. SEE TEXT PAGE 274 FOR VARIANTS.

Question 22

Where is the coronary sinus found?

Answer 22

In the posterior part of the AV groove to the right atrium