Your heart is a muscular organ that pumps blood containing the oxygen and nutrients your body needs.
The pumping sections of the heart are the right atrium, right ventricle, left atrium, and left ventricle.
In your heart, oxygen-poor blood flows from your body through large veins into your right atrium.
Next, your blood moves into your right ventricle,
which contracts, sending blood out of the heart to pick up oxygen from your lungs.
Oxygen-rich blood moves out of your lungs into your left atrium, then moves into your left ventricle.
Finally, your left ventricle contracts, sending oxygen-rich blood out of your heart to your body.