Transport In Humans: Circulatory System

11.1 Circulatory System

Definition

• Circulatory system = system of blood vessels with a pump (heart) and valves to ensure one-way blood flow.

Double Circulation

• Blood passes through the heart twice in one complete circuit:

1. Pulmonary circulation
   • Right side of heart → lungs → left side of heart.
   • Low pressure.
   • Function: exchange of CO₂ for O₂.
2. Systemic circulation
   • Left side of heart → body → right side of heart.
   • High pressure.
   • Function: delivers O₂ and nutrients to body tissues.

Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course

Importance Of Double Circulation

• Maintains higher blood pressure in systemic circulation.
• Ensures efficient oxygen delivery.
• Prevents mixing of oxygenated and deoxygenated blood.

Key Points To Remember

• Right side of heart → deoxygenated blood to lungs.
• Left side of heart → oxygenated blood to body.
• Valves prevent backflow of blood.

Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course