Basic Anatomy

Question 1

What are the vessels that arise from the Right coronary artery

Answer 1

Acute marginal branches

AV nodal artery

Posterior interventricular artery (PIV) = posterior descending artery (PDA)

Question 2

What are the vessels that arise from the Left coronary artery

Answer 2

Left anterior descending artery

Left circumflex artery

Question 3

Right dominant circulation and the percentage of people that have this

Answer 3

PIV and at least one posterolateral branch arise from RCA (80%)

Question 4

Left dominant circulation and the percentage of people that have this

Answer 4

PIV and at least one posterolateral branch arise from LCx (15%)

Question 5

Balanced cardiac circulation and the percentage of people that have this

Answer 5

dual supply of posteroinferior LV from RCA and LCx (5%)

Question 6

SA node blood supply

Answer 6

SA nodal artery, which may arise from the RCA (60%) or

LCA (40%)

Question 7

Where does venous blood enter the heart?

Answer 7

Most venous blood from the heart drains into the RA through the coronary sinus, although a small
amount drains through Thebesian veins into all four chambers

Question 8

What is the physiological effect of venous blood entering 4 chambers through Thebesian veins

Answer 8

Contributes to the physiologic R-L shunt since there is resultant deoxygenated blood on the left side of the heart

Question 9

Draw a diagram demonstrating blood pressure and corresponding LV volume, heart sounds and ECG strip

Answer 9

TN C3

Question 10

What are the layers of the heart

Answer 10

endocardium, myocardium, epicardium, visceral pericardium, pericardial cavity, parietal pericardium

Question 11

What are the semilunar valves of the heart and the number of leaflets of each

Answer 11

◆ aorti valve - 3 valve leaflets

◆ pulmonic valve - 3 valve leaflets

Question 12

What are the atrioventricular valves, what are they composed of and how many leaflets do each have

Answer 12

Subvalvular apparatus present in the form of chordae tendinae and papillary muscles

◆ Tricuspid valve - 3 valve leaflets
◆ Mitral/bicuspid valve - 2 valve leaflets

Question 13

Describe the conduction system of the heart

Answer 13

■SA node governs pacemaking control

■ anterior, middle, and posterior-internal nodal tracts carry impulses in the right atrium and along
Bachmann’s bundle in the left atrium from the SA node

■ atrial impulses converge at the AV node (except Bachmann’s bundle)
◆ the AV node is the only conducting tract from the atria to the ventricles because of electrical isolation by the annulus fibrosis (except when accessory pathways are present)

■ The bundle of His bifurcates into left and right bundle branches (LBB and RBB)

■ LBB further splits into anterior and posterior fascicles

■ RBB and fascicles of LBB give off Purkinje fibres which conduct impulses into the ventricular myocardium

Question 14

What are the annulus fibroses

Answer 14

The right and left fibrous rings of heart (anuli fibrosi cordis) surround the atrioventricular and arterial orifices

Question 15

Describe the cardiac innervation

Answer 15

■ Sympathetic nerves
◆ innervate the SA node, AV node, ventricular myocardium and vasculature
◆ SA node (β1) fibres increase pacemaking activity (chronotropy - HR)
◆ cardiac muscle (β1) fibres increase contractility (inotropy - SV)
◆ stimulation of β1- and β2-receptors in the skeletal and coronary circulation causes vasodilatation

■ Parasympathetic nerves
◆ innervate the SA node, AV node, atrial myocardium but few vascular beds
◆ basal vagal tone dominates the tonic sympathetic stimulation of the SA node and AV node
resulting in slowing of pacemaker activity and conduction
◆ parasympathetics have very little impact on total peripheral vascular resistance

Question 16

What is reduced dromotropy

Answer 16

Decreased conduction speed in the AV node