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JSS2
Basic Science

The Circulatory System

Uploaded on October 8, 2025

The Circulatory System:

What is it?

  • The Circulatory System is the body's transport system (or Cardiovascular System).

  • It ensures we stay alive and healthy by moving essential substances around.

  • Job 1 (Delivery): Oxygen and nutrients reach all body cells.

  • Job 2 (Cleanup): Waste products (like carbon dioxide and urea) are carried away.

Components of the Circulatory System

The system is made of three main parts: The Heart, Blood Vessels, and Blood.

1. The Heart (The Pump)

  • A muscular organ, about the size of a clenched fist, located in the chest.

  • Its main function is to pump blood continuously to circulate it.

  • It is divided into four chambers (Right atrium, Left atrium, Right ventricle, Left ventricle).

2. Blood Vessels (The Pipes)

These are tubes that carry blood around the body:

  • a. Arteries: Carry blood AWAY from the heart. They are thick and elastic. (Example: Aorta)

  • b. Veins: Carry blood TO the heart. They have valves to prevent blood from flowing backward. (Example: Vena Cava)

  • c. Capillaries: Tiny, thin vessels where the crucial exchange of oxygen, nutrients, and waste takes place between blood and cells.

3. Blood (The Fluid/Cargo)

A red fluid that transports materials.

  • Plasma: The yellowish liquid part; it carries nutrients, hormones, and waste.

  • Red Blood Cells (RBCs): Contain haemoglobin and carry oxygen.

  • White Blood Cells (WBCs): Fight infections and diseases.

  • Platelets: Help in blood clotting to prevent excessive bleeding.

Functions of the Circulatory System

  • 1. Transports oxygen from the lungs to the body cells.

  • 2. Carries nutrients from the digestive system to cells.

  • 3. Carries carbon dioxide and waste products away from cells.

  • 4. Helps fight diseases through White Blood Cells.

  • 5. Helps in blood clotting.


Types of Circulation

  1. a. Pulmonary Circulation: Movement of blood between the heart and the lungs. (For gas exchange.)

  2. b. Systemic Circulation: Movement of blood between the heart and the rest of the 

  3. body. (For delivery and collection.)

Diseases:

  • Common Diseases are:

    • Hypertension (High Blood Pressure): Caused by stress, obesity, etc.

    • Heart Attack: Blockage of blood flow to the heart muscle.

    • Stroke: Blocked or burst blood vessels in the brain.

    • Anaemia: Shortage of red blood cells.

  • Care of the Circulatory System:

    • Eat a balanced diet (rich in fruits/vegetables).

    • Avoid fatty foods.

    • Exercise regularly.

    • Avoid smoking and excessive alcohol.

    • Go for regular health checks.