Middle mediastinum - heart - conducting system and blood supply (Dave's notes) Flashcards
List the components of the conducting system of the heart in sequence
SA node ->atrial cardiac muscle fibres -> AV node -> AV bundle -> R and L -> subendothelial purkinje fibres
Describe the SA node. What does it contain?
The SA node is made of specialised muscle fibres. Crescent shaped, 1-2cmx5mm thick. Contains central stellate cells.
What differentiates the central stellate cells of the SA node from the rest of the myocardium?
They have fewer myofilaments than ordinary cardiac muscle.
Where is the AV node located?
Buried in the muscle of the interatrial septum.
What path does cardiac lymph follow?
Cardiac lymph follows the arteries.
Where is cardiac innervation from?
The cardiac plexus. Also NB baroreceptors
What two main arteries comprise the blood supply to the myocardium?
R) coronary artery and the L) coronary artery
Describe the path of the right coronary artery
Passes between the auricle, vertically downwards and then posteriorly
List the branches of the right coronary artery
Conus artery SA nodal artery Right marginal artery AV nodal artery Posterior interventricular artery
Describe the path of the left coronary artery
Arises behind the pulmonary trunk, dividing into the circumflex (continuation of) and anterior interventricular (LAD)
What is the conus artery a branch of? What is its path?
The RCA. Passes upwards and medial
What is the SA nodal artery a branch of.
The RCA in 60% of cases, the LCA in 40% of cases
What is the right marginal artery a branch of?
The inferior margin of the RCA
What is the AV nodal artery a branch of? Where is it found?
The RCA. Found lying posteriorly.
What is the posterior interventricular artery a branch of? What is its course?
The RCA. Passes along the interventricular groove to the apex.
List the branches of the left coronary artery
SA nodal
Circumflex
Anterior IV (LAD)
Left conus branch
What is the circumflex artery a branch of? What is its course?
The LCA. Passes down the back of the heart, giving off various branches.
What is the anterior IV (LAD) a branch of? What is its course?
Runs down in the interventricular groove, to anastomose with the posterior interventricular branch
Describe the left conus branch. What is its clinical significance?
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.
What are the diagonal and obtuse marginal branches of?
The LCA - these are several large ventricular branches given off, named diagonal and obtuse by radiologists.
What is notable about cardiac blood supply?
There is considerable variation in the way major branches end and anastomose, in particular the interventricular vessels. SEE TEXT PAGE 274 FOR VARIANTS.
Where is the coronary sinus found?
In the posterior part of the AV groove to the right atrium
