10.3 The Circulatory and Respiratory Systems

Notes

The circulatory system moves blood; the respiratory system exchanges gases. They work closely together.

• The heart has four chambers: two atria (receive blood) and two ventricles (pump blood out).
• Arteries carry blood away from the heart; veins carry blood back to the heart; capillaries are tiny vessels where exchange happens.
• Red blood cells carry oxygen using hemoglobin; white blood cells fight infection; platelets help blood clot.
• Air path: nose → pharynx → trachea → bronchi → bronchioles → alveoli.
• In the alveoli, oxygen diffuses into capillaries and carbon dioxide diffuses out to be exhaled.
• The diaphragm contracts to pull air into the lungs.