Heart Chambers and Blood Flow: Deoxygenated to Lungs & Oxygenated Return

The heart functions as a dual pump: **right side** (pulmonary circuit) and **left side** (systemic circuit). Blood flows in a precise sequence:

Deoxygenated Blood Path (Systemic → Pulmonary)

1. Superior/Inferior Vena Cava → Right Atrium (RA).
2. Tricuspid Valve → Right Ventricle (RV).
3. Pulmonary Valve → Pulmonary Trunk → Right/Left Pulmonary Arteries → **Lungs** (gas exchange: CO₂ out, O₂ in).

Oxygenated Blood Path (Pulmonary → Systemic)

1. Pulmonary Veins (4) → Left Atrium (LA).
2. Mitral (Bicuspid) Valve → Left Ventricle (LV).
3. Aortic Valve → **Aorta** → Systemic arteries → Capillaries → Tissues.

Key Features

• **Valves** prevent backflow (AV: tricuspid/mitral; Semilunar: pulmonary/aortic).
• **Coronary Circulation:** Right/Left coronary arteries arise from aortic root → supply myocardium.
• **Pressure Differences:** RV/LV generate ~25/120 mmHg respectively (systemic resistance >> pulmonary).
• **Fetal Circulation:** Foramen ovale, ductus arteriosus bypass lungs; close after birth.

Clinical Correlates

• Shunts (ASD, VSD, PDA) mix circuits → cyanosis/heart failure.
• Valve stenosis/regurgitation alters flow dynamics.
• Pulmonary embolism blocks pulmonary artery → right heart strain.