✧ circulation

• the heart has four chambers, two atria (upper) and two ventricles (lower)
• the heart is located between the lungs
• deoxygenated blood enters the right atrium through the superior vena cava or inferior vena cava
• from the right atrium, deoxygenated blood passes into the tricuspid valve and then into the right ventricle
• the septum separates the right and left sides of the heart
• blood from the right atrium passes into the tricuspid valve which leads to the right ventricle
• from the left atrium, oxygenated blood passes into the bicuspid valve and then into the left ventricle
• blood flows from the right side to the left side
• in the lungs, carbon dioxide diffuses out of the bloodstream and into the alveoli while oxygen diffuses into the bloodstream
• the heart consists of four chambers - two atria (right and left) and two ventricles (right and left)
• when the heart contracts, it pumps blood through the pulmonary artery into the lungs where gas exchange occurs