(Hank playing Operation)

Gah! Cavity Sam here is not doing so great. He's got junk in his body that definitely should not be there. But, you know, like the fork and the knife in the belly and the heartburn and the jackhammer head are easy problems to fix because Sam's body does not come close to the incredible complexity of what's going on inside of you right now.

Your body is awesome, literally. The amount of stuff going on at any given time to keep you alive and functioning is awe-inspiring. Trying to manipulate the tiny little tweezers so you can retrieve the nail from poor Sam's fingers is nothing compared to the challenge of just trying to understand the systems that keep you operating. The human body is composed of thousands of intricate pieces of biological machinery, which is part of why we rely on two twin disciplines to talk about it here on Crash Course: anatomy and physiology. Anatomy is the study of the structure and relationships between body parts, while physiology is the science of how those parts come together to function and keep that body alive.

From grave robbers to microscopes, these fascinating disciplines have come a long way and we are still discovering new things about how it all works. I'm not going to lie to you, it's tough. We'll build on things that you learned in biology and chemistry and you'll learn more about cell specialization, how your epithelial tissue creates order out of the mayhem of your body, and look at the important protection you get from your integumentary system. And by the end of this course you're gonna understand more about all of the complicated things your body is up to right now while you're sitting there at home watching this video, and maybe you'll appreciate what a wondrous thing that body of yours truly is.

To be clear, that is not a real x-ray. It's Photoshop.

So join us for a new year of Crash Course where I, Hank Green, talk about all of this... stuff and hopefully help us all understand a little more about ourselves with Crash Course: Anatomy and Physiology.

(Game buzzes) Duh! Homeostasis.