Pathway of blood flow through the heart

step 1

blood enters right atrium from superior and inferior venae cavae

step 9

blood flows through aortic valve into ascending aorta

step 4

blood flows through pulmonary valve into pulmonary trunk

step 10

blood in aorta is distributed to every organ in the body, where it unloads O2 and loads CO2

step 2

blood in right atrium flows through right AV valve into right ventricle

step 7

blood in the left atrium flows through left AV valve into left ventricle

step 5

blood is distributed by right and left pulmonary arteries to the lungs where it unloads CO2 and loads O2

step 6

blood returns from the lungs via pulmonary veins to left atrium

step 11

blood returns to right atrium via venae cavae

step 8

contraction of left ventricle (simultaneous with step 3) forces aortic valve open

step 3

contraction of right ventricle forces pulmonary valve open