Major Vessels of the Heart

Arteries carry oxygenated blood away from the heart (except pulmonary arteries).
Veins bring deoxygenated blood to heart (except pulmonary veins).
Vena cava (inferior & superior) is the main vessel feeding the heart and delivers approx. 65% of volume from the venous system. 
Blood flows from the heart into arteries, arterioles, capillaries, venules, veins, back to heart.
Increased energy demands (i.e. exercise) require increased blood flow.
SNS (sympathetic nervous system) stimulation is responsible for majority of fluctuations in flow during exercise (vasodilation and vasoconstriction simultaneously).

Blood flow through the vessels of the heart

Deoxygenated blood from Inferior & Superior vena cava and the Coronary sinuses flows into Rt atrium -> Tricuspid valve -> Rt ventricle -> Pulmonic valve -> Pulmonary artery -> Pulmonary circulation into lungs (picks up O2).

Oxygenated blood from Pulmonary veins flows into Lt atrium -> Mitral valve -> Lt ventricle -> Aortic valve -> Aorta -> Systemic circulation (gives up O2).

Rt ventricle ejects blood thru Lt & Rt pulmonary arteries to lungs.
Lt ventricle ejects blood into aortic arch to body (from the arch 3 main arteries branch to brain (carotids) and upper thorax (subclavian artery).

Coronary Arteries

Heart’s own blood supply that begin at epicardium and ends at endocardium.                                                                                               Blood flows into coronary arteries during diastole.                                                                                                                                         Distribute O2 and nutrients.  Even at rest cardiac cells extract 75% of O2 from coronary arteries.                                                      Heart is entirely dependent on these arteries for any increases on cardiac workload.

RCA( right coronary artery) comes from aorta. Serves Rt atrium, ventricle, SA node, AV node. 
Left main – from left border of aorta opposite to RCA.                                                                                                             
Splits into 2 arteries:  Circumflex – wraps around surfaces of heart (also serves SA and AV node.                                                                                                    Left anterior descending – travels down anterior surface of Lt ventricle.
Coronary veins drain into Rt atrium via coronary sinus.

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