How the Cardiovascular System Transports Oxygen Throughout the Body

The cardiovascular system—heart, blood vessels, and blood—forms a closed circuit that continuously delivers oxygen to tissues and removes carbon dioxide.

Step-by-Step Oxygen Transport

1. Deoxygenated blood return: Systemic veins → superior/inferior vena cava → right atrium
2. Pulmonary circulation: Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary arteries → lung capillaries (alveoli)
3. Gas exchange in lungs: CO₂ diffuses out; O₂ binds to hemoglobin in red blood cells (each Hb binds 4 O₂)
4. Oxygenated blood distribution: Pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta → systemic arteries → arterioles → tissue capillaries
5. Tissue oxygen delivery: O₂ dissociates from hemoglobin, diffuses into cells for mitochondrial ATP production
6. CO₂ return: CO₂ (as bicarbonate, dissolved, carbamino-Hb) travels via veins back to step 1

Key Adaptations

• Hemoglobin: ~150 g/L in blood; cooperative binding enables efficient loading (lungs) and unloading (tissues)
• Bohr effect: Low pH/high CO₂ in tissues promotes O₂ release
• Capillary density: Matches metabolic demand (high in heart, brain, muscle)

This continuous, unidirectional flow—powered by the heart's dual-pump action—sustains cellular respiration in every tissue.