Cardiovascular system

The wall of the heart has three layers. Which of the following is the thickest layer responsible for contraction?

Endocardium

Myocardium

Epicardium

Pericardium

Which of the following valves prevents backflow of blood from the left ventricle to the left atrium?

Pulmonary valve

Aortic valve

Mitral valve

Tricuspid valve

The pacemaker of the heart is:

Atrioventricular (AV) node

Purkinje fibers

Sinoatrial (SA) node

Bundle of His

Which blood vessels carry oxygenated blood from the lungs to the heart?

Pulmonary veins

Pulmonary arteries

Superior vena cava

Coronary veins

During ventricular systole, which of the following occurs?

Atria contract and push blood into ventricles

AV valves open, semilunar valves close

Ventricles contract and semilunar valves open

Both atria and ventricles relax

Cardiovascular system

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