The heart

Left atrium

Chamber of the heart that receives oxygen-rich blood from the lungs through the pulmonary veins.

Mitral (bicuspid) valve

Valve between the left atrium and left ventricle that prevents blood from flowing backward.

Left ventricle

Heart chamber that pumps oxygenated blood to the body through the aorta.

Aorta

Largest artery that carries oxygen-rich blood from the left ventricle to the rest of the body.

Systemic arteries

Blood vessels that carry oxygenated blood away from the heart to body tissues.

Systemic capillaries

Tiny blood vessels in body tissues where gas exchange occurs between blood and cells.

Gas exchange (systemic)

Process where oxygen diffuses from the blood into body cells and carbon dioxide diffuses from cells into the blood.

Venules

Small blood vessels that collect deoxygenated blood from capillaries.

Veins

Blood vessels that return deoxygenated blood to the heart.

Superior and inferior vena cava

Large veins that carry oxygen-poor blood from the body back to the right atrium.

Right atrium

Heart chamber that receives deoxygenated blood from the body.

Tricuspid valve

Valve between the right atrium and right ventricle that prevents backflow of blood.

Right ventricle

Heart chamber that pumps deoxygenated blood to the lungs.

Pulmonary valve

Valve that controls blood flow from the right ventricle into the pulmonary artery.

Pulmonary artery

Blood vessel that carries deoxygenated blood from the heart to the lungs.

Pulmonary capillaries

Tiny blood vessels surrounding the alveoli where gas exchange occurs in the lungs.

Alveoli

Small air sacs in the lungs where oxygen and carbon dioxide are exchanged.

Gas exchange (pulmonary)

Process where carbon dioxide diffuses out of the blood and oxygen diffuses into the blood in the lungs.

Pulmonary veins

Blood vessels that carry oxygen-rich blood from the lungs back to the left atrium.

Concentration gradient

Difference in gas concentration that allows oxygen and carbon dioxide to diffuse across membranes.

Thin membranes

1-cell-thick walls of capillaries and alveoli that allow gases to diffuse easily.

Large surface area

Many capillaries and alveoli that increase the efficiency of gas exchange.