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Unit: Human biology

As humans, we really like breathing oxygen. That's because the cells in our body will die if they don't get the oxygen they need to function. This tutorial describes how gases are exchanged between blood and the atmosphere in our lungs, and how oxygen is then pumped through the body by way of blood and the circulatory system.
How do we get unwanted substances out of our blood? Through the kidney. This tutorial goes into detail about how the kidney works.
Without muscles, we wouldn't be able to do much of anything. This tutorial explores what muscle cells are and how they contract to let us move our bodies.

About this unit

Your body is an amazing system! The human body is made up of groups of organs, called organ systems, that work together to keep the body in balance. In this section, we'll travel from the circulatory system, to the nervous system, to the immune system and beyond. Learn about the amazing biology that keeps your body ticking!