For most of history, scientists weren't quite sure why our hearts were beating or even what purpose they served. Eventually, we realized that these thumping organs serve the vital task of pumping clean blood throughout the body. But how?...

Paul Andersen explains how feedback loops allow living organisms to maintain homeostasis. He uses thermoregulation in mammals to explain how a negative feedback loop functions. He uses fruit ripening to explain how a positive feedback...

Today we’ll explore how sociology defines family and the different terms used to describe specific types of family. We’ll look at marriage in different societies, as well as marital residential patterns and patterns of descent. And, of...

High elevations can be a problem for humans. Since the air is thinner, you get less oxygen with every breath, leading to all kinds of negative side effects. But there are millions of people around the world who spend their whole lives at...

In 1987, thousands of people gathered in Saudi Arabia for the annual Hajj pilgrimage. But what started out as a celebration led to a worldwide health crisis: more than 2,000 cases of meningitis broke out, spreading across Saudi Arabia...

Your cell phone is mainly made of plastics and metals. It's easy to appreciate the process by which those elements add up to something so useful. But there's another story we don't hear about -- how did we get our raw ingredients in the...

Paul Andersen describes four important homeostatic loops in biology. He begins with a brief description of the elements of a homeostatic loop. He then describes how the hypothalamus helps us maintain a stable internal body temperature....

Clinical Sexologist and Sexplanations Host Lindsey Doe teaches Hank the difference between HIV and AIDS. Then Chinchilla Ash teaches Hank about softness.

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Paul Andersen explains how epinephrine is responsible for changes in chemistry of our body associated with the fight or flight response. Epinephrine released by the adrenal medulla are received by a number of organs associated with the...

Today on Crash Course Anatomy & Physiology, Hank breaks down the parts and functions of one of your body's unsung heroes: your epithelial tissue.
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Epithelial Tissue Creates...

Paul Andersen explains how organisms regulate their internal osmolarity or not. He starts with a brief description of osmosis and why it is important for animal cell to be surrounded by an isotonic solution. He then explains how...

Between you and the rest of the world lies an interface that makes up 16% of your physical weight. This is your skin, the largest organ in your body: laid out flat, it would cover close to 1.7 square meters of ground. But besides keeping...

At this moment, three hundred million women across the planet are experiencing the same thing: a period. The monthly menstrual cycle that gives rise to the period is a reality that most women on Earth will go through in their lives. But...

Bones might seem rock-solid, but they’re actually quite porous inside. Most of the large bones of your skeleton have a hollow core filled with soft bone marrow. Marrow's most essential elements are blood stem cells and for patients with...

Each time you take a step, 200 muscles work in unison to lift your foot, propel it forward, and set it down. It's just one of the many thousands of tasks performed by the muscular system: this network of over 650 muscles covers the body...

Hank takes us on the fascinating journey through our excretory system to learn how our kidneys make pee.

You put a dying person in suspended animation until, possibly thousands of years from now, medical science is able to cure them... or their brain can be put in a sweet robot body. It's an age-old sci-fi trope, but there are scientists...

Humans’ experiences with ventilators have taught us that sighing isn’t just a way to express yourself: it’s a vital part of our everyday breathing.

Our skin is the largest organ in our bodies, with a surface area of about 20 square feet in adults. When we are cut or wounded, our skin begins to repair itself through a complex, well-coordinated process. Sarthak Sinha takes us past the...

Today we're going to discuss the Binomial Distribution and a special case of this distribution known as a Bernoulli Distribution. The formulas that define these distributions provide us with shortcuts for calculating the probabilities of...

Quick Questions explains why, when it comes right down to it, there are really only eight kinds of people in the world.

Paul Andersen discusses the specifics of phylogenetics. The evolutionary relationships of organisms are discovered through both morphological and molecular data. A specific type of phylogenetic tree, the cladogram, is also covered.

If you don't have vision problems, getting an eye exam probably hasn't been your top priority, however visiting an ophthalmologist won't just tell you about your eyes, it can reveal a lot about your health.

Paul Andersen explains the importance and location of interstitial fluid. He describes both the hydrostatic and osmotic pressures that move fluid between the interstitial fluid and the capillary. He also explains the major function of...