Learning objectives

• Know the main parts of the circulatory system: heart, blood, and blood vessels.
• Understand the main functions: transport, protection and temperature control.
• Be able to measure pulse and explain why a healthy lifestyle helps the circulatory system.

Short introduction

The circulatory system moves blood around your body. Blood carries oxygen and food to all the cells and takes away waste like carbon dioxide. The heart is the pump that keeps blood moving through tubes called blood vessels.

Main parts

• Heart — a muscular organ that pumps blood. It is about the size of your fist.
• Blood — made of red blood cells, white blood cells, platelets and plasma.
• Blood vessels — tubes that carry blood:
  • Arteries (red) carry blood away from the heart — usually rich in oxygen.
  • Veins (blue) carry blood back to the heart — usually carrying waste and carbon dioxide.
  • Capillaries — tiny vessels where exchange of oxygen and waste happens with body cells.

Simple diagram

What is in blood? (simple view)

Functions of the circulatory system

• Transport: brings oxygen and food to cells and removes wastes like carbon dioxide.
• Protection: white blood cells fight infections; platelets help stop bleeding.
• Temperature control: moves heat around the body to keep you warm or cool.

Classroom activity: Measure your pulse

1. Sit quietly for 5 minutes.
2. Place your first two fingers on the inside of your wrist (thumb side) or on your neck beside your windpipe.
3. Count the beats you feel for 15 seconds. Multiply by 4 to get beats per minute (bpm).
4. Record result. A normal resting rate for children (about 6–15 years) is around 70–100 bpm.
5. Try again after 5 minutes of running or playing and compare the numbers.

Simple classroom model: Balloon heart

You can make a simple model of the heart using two balloons and a small pump or by squeezing a balloon to show pumping. Use red and blue straws to show arteries and veins and see how the "heart" pushes water (blood) through them.

Health and Kenyan context

• Eat balanced food such as ugali with vegetables and beans, fruits, and clean water to keep your blood healthy.
• Regular exercise (games, running, jump rope) keeps your heart strong.
• Diseases like malaria affect the blood. If you get sick, tell an adult and seek care at a nearest health centre.

Key words

Heart • Blood • Arteries • Veins • Capillaries • Red blood cells • White blood cells • Platelets • Pulse

Quick review questions

1. What are the three main parts of the circulatory system?
2. Which blood vessels carry blood away from the heart?
3. What do red blood cells do?
4. How can you measure your pulse?
5. Name one way to keep your circulatory system healthy.