Cells, Tissues & Organs
Understand that the body is organised in a hierarchy: tiny cells are the building blocks, groups of similar cells form tissues, tissues combine into organs (like the heart or stomach), and organs work together in organ systems (like the circulatory system)
What a learner can do afterwards
- State that cells are the smallest building blocks of the body, too small to see without a microscope
- Describe the hierarchy: cells → tissues → organs → organ systems
- Give an example: muscle cells form muscle tissue, which forms the heart organ, which is part of the circulatory system
The lesson
Your body is made of trillions of tiny living parts called cells. Cells are so small that you cannot see even one without a special tool called a microscope. Everything in your body, your heart, your brain, your lungs, starts out as cells.
When many similar cells group together, they form a tissue. When different tissues work together, they form an organ, like your heart or your stomach. When organs team up to do one big job, they form an organ system.
Think about your heart. Tiny muscle cells join together to make muscle tissue. That muscle tissue, plus other tissues, makes the heart, an organ. The heart works with your blood vessels to form the circulatory system, which moves blood all around your body.
When you learn about a body part, ask yourself: is this a cell, a tissue, an organ, or a whole system working together?
Cells are tiny building blocks that group into tissues, tissues build organs, and organs team up to form organ systems.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.