The Heart
What Is the Heart?
The heart is a muscular organ that pumps blood around the body through the circulatory system.
It delivers oxygen and nutrients to cells and removes carbon dioxide and waste.
💡 Key Concept: The heart is a double circulatory system – one circuit sends blood to the lungs, and the other sends blood to the rest of the body.
Structure of the Heart
The heart has four chambers:
Chamber | Function |
Right atrium | Receives deoxygenated blood from the body via the vena cava |
Right ventricle | Pumps deoxygenated blood to the lungs via the pulmonary artery |
Left atrium | Receives oxygenated blood from the lungs via the pulmonary vein |
Left ventricle | Pumps oxygenated blood to the body via the aorta |
Valves in the Heart
✔ Prevent backflow of blood
✔ Ensure one-way flow
✔ Found between atria and ventricles, and at the exits of the heart
Major Blood Vessels
Vessel | Function |
Vena cava | Carries deoxygenated blood from the body to the heart |
Pulmonary artery | Carries deoxygenated blood from the heart to the lungs |
Pulmonary vein | Carries oxygenated blood from the lungs to the heart |
Aorta | Carries oxygenated blood from the heart to the body |
💡 The left ventricle has a thicker wall than the right because it must pump blood all around the body, not just to the lungs.
Double Circulatory System
1️ Pulmonary circuit
✔ Right side of the heart
✔ Sends blood to the lungs to collect oxygen and remove CO₂
2️ Systemic circuit
✔ Left side of the heart
✔ Sends oxygenated blood to the rest of the body
💡 This system is efficient – oxygenated and deoxygenated blood don’t mix.
Questions
- How many chambers does the heart have?
- What does the pulmonary artery do?
- Why does the left ventricle have a thicker wall?
- What do valves in the heart do?
- Which blood vessel brings oxygenated blood back from the lungs?
Summary
- The heart pumps blood in a double circulatory system – to the lungs and body.
- It has four chambers and is connected to major blood vessels.
- Valves ensure blood flows in one direction.
- The left side pumps oxygenated blood; the right side handles deoxygenated blood.