Blood Carries Oxygen and Food to Every Cell
Medi stands inside a giant glowing red tunnel shaped like a blood vessel, holding a tray of tiny oxygen bubbles and nutrient packets, pointing excitedly as a cartoon red blood cell zooms past carrying its delivery toward a waiting muscle cell at the tunnel's far end.
- Explain what job the circulatory system does inside the body.
- Identify the three main parts of the circulatory system: heart, blood vessels, and blood.
- Describe how blood picks up oxygen in the lungs and delivers it to body cells.
- Explain how blood carries away waste products that cells do not need.
- Compare blood vessels to tubes that form a delivery network throughout the body.
Key terms
- circulatory system
- the team that moves blood around you
- heart
- a strong muscle that pumps your blood
- blood vessel
- a tube that carries your blood
- artery
- a tube carrying blood away from the heart
- red blood cell
- a tiny cell that carries oxygen
The Delivery Team
Every cell in your body needs oxygen and food to stay alive. Your circulatory system delivers them. It has three parts. The heart is a muscle about the size of your fist that pumps blood all day. Blood vessels are the tubes that carry blood everywhere. Blood is the delivery truck, with red blood cells that carry oxygen to every part of you.
One Delivery Trip
First, blood goes to your lungs, where red blood cells pick up fresh oxygen. Then your heart pumps that blood through arteries to every cell, even in your toes. The blood drops off oxygen and food, then picks up carbon dioxide waste. Last, blood travels back to the heart through veins to start the whole trip again.
Worked examples
How does oxygen reach a cell in your toe?
- Red blood cells pick up oxygen in the lungs.
- The heart pumps the blood out through arteries.
- Blood travels all the way down to your toe.
- The blood drops off oxygen at the toe cell.
Answer: Blood carries oxygen from the lungs to the toe cell.
Activity
Sort each item into the correct stop on the blood's delivery route: Lungs, Heart, Body Cell, or Blood Vessel.
Practice
What two things does blood deliver to your cells?
Where do red blood cells pick up fresh oxygen?
Common mistakes to avoid
- Blood only carries oxygenBlood also carries food to cells and carries waste away.
- The heart sends blood without tubesBlood vessels are tubes that carry blood everywhere it goes.
Check your understanding
What is the main job of the circulatory system?
A student says, 'Blood only carries oxygen — it does not carry food or waste.' What is wrong with that idea?
Where do red blood cells pick up fresh oxygen before delivering it to the rest of the body?
Recap
Your circulatory system has a heart, blood vessels, and blood. Blood picks up oxygen in the lungs, delivers oxygen and food to cells, and carries waste away around and around.
Reflect
Picture blood zooming through you to feed every cell!