If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Unit 28: Principles of physiology

About this unit

How is your body organized? How do your organ systems work together to keep you running? What keeps your blood at the right pH or your body at the right temperature? Learn more about tissues, organs, and organ systems and the control mechanisms that keep internal conditions steady in humans and other animals.

What makes a tissue different from an organ? How does your stomach collaborate with your small intestine to make sure you get nutrients? And most important, how do the systems of your body keep things like your temperature and blood pH from getting too high or too low? Keep reading and watching to find answers to all of these questions!
You may think of metabolism as something that humans have (such as a fast or a slow metabolism). But metabolism is just the sum total of chemical reactions that occur in an organism's body, and all organisms must metabolize to keep their bodies running. Learn more about metabolism and how it's connected to thermoregulation (temperature regulation) in different species of animals.