Circulatory System — Key English Terminology

1.Right atrium receives blood from superior and inferior vena cava. Right ventricle pumps blood to the pulmonary arteries. Left atrium receives oxygenated blood from the pulmonary veins. Left ventricle pumps blood to the aorta and has the thickest wall.

2.Tricuspid valve sits between right atrium and right ventricle. Bicuspid or mitral valve sits between left atrium and left ventricle. Pulmonary semilunar valve guards the right ventricle to pulmonary artery exit. Aortic semilunar valve guards the left ventricle to aorta exit.

3.Conduction sequence: SA node, then AV node, then bundle of His, then bundle branches, then Purkinje fibers.

4.Sinoatrial SA node is the natural pacemaker, firing at sixty to one hundred beats per minute. Atrioventricular AV node delays conduction so atria finish contracting first; backup rate is forty to sixty.

5.Why is the SA node the pacemaker? Because it has the fastest intrinsic firing rate, dominating the entire cardiac rhythm. If SA fails, AV takes over but slower.

6.Pulmonary artery carries DEoxygenated blood — the only artery that does so. Pulmonary vein carries oxygenated blood — the only vein that does so. Aorta carries the most oxygenated blood. Vena cava carries deoxygenated blood.

7.Exam trap: arteries and veins are defined by leaving or returning to the heart, not by oxygenation status.

8.Full pathway: right atrium, right ventricle, pulmonary artery, lungs for gas exchange, pulmonary vein, left atrium, left ventricle, aorta, systemic circulation, vena cava, back to right atrium.

9.Artery: thick wall, elastic, smooth muscle — withstands high pressure. Capillary: single layer of endothelial cells — site of substance exchange. Vein: thin wall with valves — low-pressure return flow.

10.Clotting cascade: vascular spasm, platelet plug, coagulation cascade with clotting factors, then fibrin mesh — prothrombin to thrombin to fibrinogen to fibrin.

11.Vitamin K is essential cofactor for synthesizing clotting factors two, seven, nine, and ten. Deficiency causes bleeding tendency. Warfarin is a vitamin K antagonist.