Blood – Oil for Your Body

The engine in your mom’s car has oil. The oil does lots of things. It keeps the engine clean and it keeps things running smoothly. Your blood is a little like engine oil, but even better. Blood carries oxygen and nutrients to all the cells in your body so they can grow and stay healthy. It carries waste products away from your cells so they stay clean. Blood even helps you get better when you’re sick.

Blood is made in the marrow of certain bones. This marrow is soft – sort of like jelly. Blood vessels in the bone carry the new blood cells to the rest of your body.

Blood Composition Image - Science for Kids All About Blood
All About Blood: Main Components of Human Blood

Fun Facts about Blood for Kids

  • Blood is made up of four parts – plasma, red cells, white cells and platelets. Each part has a special job.
  • Plasma is a yellow liquid. It helps give you energy and grow.
  • Red blood cells carry oxygen to your cells.
  • White blood cells clean the blood and fight germs. When a virus enters your body, white blood cells rush to destroy the virus so you get better.
  • Platelets help your blood clot. When you cut yourself, a clot forms so the blood stops running. If your blood didn’t clot, you could bleed to death.
Components of Blood Image
Percentage of different blood components

Blood Vocabulary

  1. Oxygen: a gas we need to live. Oxygen gives energy to our cells so we can grow and thrive
  2. Waste: things our bodies can’t use
  3. Vessel:  thin pipe surrounded by muscle that carries blood
  4. Plasma: a yellow liquid that delivers nutrients to the body
  5. Virus: a small organism that can make you sick
Blood Vessel Arrangement Image
Blood Vessels Arrangement and Functions

Learn More All About Blood and Human Transportation System

Check out this video all about blood and the human transportation system:

A video presentation about the main functions of blood in the human body.

Blood Q&A

Question:  Are blood vessels all the same size?

Answer: Some blood vessels, called capillaries, are thinner than a hair. Major arteries are much larger. Veins are in between.


Question: How much blood is in your body?

Answer: Between six and eight pints, depending on your age.


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