Human Heart Anatomy: Four Chambers, Dual Circulation

The human heart has four chambers—not two—and operates as a dual (double) circulatory system.

Chamber Functions

Chamber	Receives	Pumps To	Blood Type
Right atrium	SVC, IVC, coronary sinus	Right ventricle	Deoxygenated (systemic return)
Right ventricle	Right atrium	Pulmonary artery → lungs	Deoxygenated
Left atrium	Pulmonary veins (4)	Left ventricle	Oxygenated (pulmonary return)
Left ventricle	Left atrium	Aorta → systemic circulation	Oxygenated

Dual Circulation Advantages

• Complete separation of oxygenated/deoxygenated blood.
• High-pressure systemic flow (LV generates 120 mmHg) without damaging delicate pulmonary capillaries (RV generates 25 mmHg).
• Efficient O₂ delivery to meet high metabolic demands of endothermy.

Valves Ensure Unidirectional Flow

• Tricuspid (RA→RV), Pulmonary (RV→PA)
• Mitral (LA→LV), Aortic (LV→Ao)

Clinical Correlate

Congenital defects (VSD, ASD, PDA) allow mixing → cyanosis, heart failure. Single-ventricle physiology requires staged surgical palliation (Fontan).