Now that we've talked about your blood vessels, we're going to zoom in a little closer and talk about your blood itself. We'll start by outlining the basic components of blood -- including erythrocytes, leukocytes, platelets, and plasma...

Paul Andersen explains the importance of blood types in blood transfusions. He starts with a brief discussion of blood antigens and antibodies. He describes how the ABO differs from the Rh blood type. He shows you how to solve simple...

We've compiled our videos about sugar and sweetness here. Enjoy the rush!

Today Hank explains the skeletal system and why astronauts Scott Kelly and Mikhail Kornienko are out in space studying it. He talks about the anatomy of the skeletal system, including the flat, short, and irregular bones, and...

Jessi and Squeaks adopted a new fish! They have him all set up in a nice fish tank, but now they have a big question: how do fish breathe underwater?!

Our final unit of Crash Course Sociology is medical sociology. Today we’ll explain what it is and get an overview of the role of society in our notions of health and disease.

If you lined up all the blood vessels in your body, they'd be 60 thousand miles long. And every day, they carry the equivalent of over two thousand gallons of blood to the body's tissues. What effect does this pressure have on the walls...

Thanks to the University of Minnesota for sponsoring this video!

Lyme disease is spreading like wildfire around the world: here's...

What killed George Washington? Turns out it was probably related to the bloodletting and other 18th-century medicine his doctors applied.

Find out why these arachnids are among the least B of humanity's BFFs. Yeah, they're blood-sucking parasites, but that's not all of it!

A new virus emerges and spreads like wildfire. In order to contain it, researchers must first collect data about who's been infected. Two main viral testing techniques are critical: one tells you if you have the virus and the other shows...

Every time you breathe, air travels down the trachea, through a series of channels, and then reaches little clusters of air sacs in the lungs. These tiny sacs facilitate a crucial exchange: allowing oxygen from the air we breathe into...

Blood banks need a constant supply of donors to maintain their supply, but some enzymes that are already in our bodies might be able to help!

Hank gives you at least three reasons to like mosquitoes even less than you do already, and tells you how you can literally decrease world suck by fighting mosquito-borne disease.

Splinters are gross, but you might want to watch this before grabbing the tweezers.

If you've heard it once, you've heard it a thousand times: Parents blaming their kids' active behavior on sugar. But is it true? Hank gives you sweet-and-lowdown on the extent to which sugar can and can't affect behavior, in kids and...

Get to know your body’s most important muscle -- your heart -- and learn how to take your own pulse!

While you unwrap that luscious truffle, let Hank explain the science of chocolate -- where it comes from, what its active ingredient is, and how it works. Also learn the difference between chocolate, cocoa, cacao and coca, so you really...

Paul Andersen details examples of natural selection in the world. He starts by explaining how changes in global temperatures are causing plants to adapt. He explains how mutations cause changes in phenotype which give organisms varying...

Water is essentially everywhere in our world, and the average human is composed of between 55 and 60% water. So what role does water play in our bodies, and how much do we actually need to drink to stay healthy? Mia Nacamulli details the...

It's an increasingly common sight in hospitals around the world: a nurse measures our height, weight, blood pressure, and attaches a glowing plastic clip to our finger. Suddenly, a digital screen reads out the oxygen level in our...

Hank begins teaching you about your endocrine system by explaining how it uses glands to produce hormones. These hormones are either amino-acid based and water soluble, or steroidal and lipid-soluble, and may target many types of...

In the second half of our look at the endocrine system, Hank discusses chemical homeostasis and hormone cascades. Specifically, he looks at the hypothalamus-pituitary-thyroid axis, or HPT axis, and all the ways your body can suffer...

Virus hunter Nathan Wolfe is outwitting the next pandemic by staying two steps ahead: discovering deadly new viruses where they first emerge -- passing from animals to humans among poor subsistence hunters in Africa -- before they claim...