Blood leaves the heart at speeds around 12-16 miles per hour

An interactive guide to the cardiovascular system

The cardiovascular or circulatory system moves blood throughout the body, ensuring cells have necessary nutrients and removing any waste. Click through this interactive 3D guide to explore the system as it crisscrosses the body via arteries, veins, and capillaries. This guide also includes similar breakdowns of the body and its other processes.

Explore the heart in this interactive 3D model

The heart is the fleshy muscle at the heart (pun intended) of the circulatory system. The heart is segmented into four chambers: two for intake (the right side) and two for output (the left side). Controlled via the autonomic nervous system, also known as the involuntary nervous system, the heart typically beats 60 to 100 times per minute, sending nutrient- and oxygen-rich blood throughout the body.

Blood pressure readings correspond to the peaks and valleys of heart beats

Pushing 2,000 gallons of blood through the body every day exerts a force known as blood pressure. Blood pressure is highest during the heart's contractile phase, known as systole, which forces blood through the circulatory system, and lowest during the heart's resting phase between beats, known as diastole.

Blood transports oxygen and vital nutrients throughout the body

Blood is the most vital substance in a body, ferrying oxygen, nutrients, and hormones to cells in need while regulating body temperature and collecting cellular waste and byproducts, such as carbon dioxide, for removal. Every adult human has over a gallon of the red liquid coursing through their veins.

Seven things you might not know about blood

The red stuff currently pumping throughout your body is a type of connective tissue that is both a solid and a liquid. The liquid portion—plasma—acts as a carrier for the solid portion, which includes blood cells and their biological brethren. Your body is constantly refreshing its supply of blood, creating new cells to replace those that have expired or died. This article overviews some lesser-known facts about blood (and why it's not always red).

What does a beating human heart look like?

Tucked behind your rib cage and between your lungs sits your heart. This knot of cardiac muscle will (typically) beat billions of times throughout your lifetime, sending oxygenated and nutrient-rich blood throughout the body, powering countless biological processes that have enabled you to read this very paragraph. This two-minute video provides a glimpse of the mechanics happening inside your chest via an animated anatomical model.

Ten things to know about your heart

Your heart does amazing things day in and day out. Its main job is crucial: It keeps oxygenated blood circulating throughout your body. Did you know that, other than your cornea, every cell in your body gets blood from your heart? You may not think...

See how the Ebola virus affects blood circulation in the human body

Ebola infects and disables immune cells, causing a cascade of events that result in small blood clots throughout the body, weakening blood vessels, and interrupting blood flow to key organs.

Pregnancy causes a woman's blood volume to increase by up to 50%

This change, to support the developing fetus, puts stress on the heart and blood vessels. A pregnant woman's heart rate also increases as she pumps more blood each minute to support fetal growth.

What is cardiovascular disease?

Cardiovascular diseases are a range of related health conditions that develop in the heart and blood vessels. This article and related infographics detail cardiovascular disease types and treatments.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

Blood evolved many times over hundreds of millions of years

The earliest evidence of a blood-like substance comes from ancient arthropods, which appear to have had copper-based blood. In the 500 million years since then, some creatures have grown to rely on other variants, such as humanity's iron-based blood.

Donated hearts remain viable three times longer now with new tech

Advances in organ perfusion systems have significantly lengthened the amount of time donated hearts can remain viable for transplant, expanding the possibilities for donor organs to wider geographic areas. "Heart in a box" devices, developed in recent years, enable effective oxygen flow in the donor heart during transport, which means that hearts can now travel farther to potential recipients and still be in good condition.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

What is the blood brain barrier?

Every blood vessel is lined with endothelial cells that act as filters between blood and the rest of the body. In the brain, these cells are tightly packed together to keep a close watch on what substances can access the vital organ. This protective measure poses an obstacle to drugmakers looking to deliver drugs to the well-defended brain for conditions like Alzheimer's. Watch a quick overview here.

How does food move through the body?

Food passes through the digestive system via muscle movement known as peristalsis, during which a rippling contraction slowly pushes content through tubular organs, such as the esophagus and intestines. This is similar to what happens when one squeezes a tube of toothpaste, contracting the tube behind the content and forcing the tube in front of the content to expand, allowing the content to move forward.

Each part of the human body experiences aging differently

With global average life expectancy cresting at 73 years, understanding how the body ages is imperative to effective medical treatment and maintaining a desired quality of life. This 13-minute video dives into how the body and its organs age "from head to toe."

Transpiration drives water movement through a plant’s vascular system

Water evaporates from the leaves, creating tension that pulls more water upward from the roots through the xylem—the equivalent of plant blood vessels. This process is supported by water molecules sticking to each other (cohesion) and xylem walls (adhesion).

How much your blood really costs

In the US, donating plasma twice a week can earn you $400 a month. But this system only works by targeting people who need the money most. Plasma clinics are placed in low-income zip codes, and frequent donation may increase health risks.

Hemorrhagic strokes make up roughly 13% of stroke events

A hemorrhagic stroke occurs when a faulty blood vessel within the brain bleeds. Though this is less common than an ischemic stroke, it is often far more deadly. This in-depth resource from the American Stroke Association provides a comprehensive overview of the two main subtypes of hemorrhagic stroke along with a useful animation of the condition.

Watch a video that visualizes what really happens inside a credit card network when you make a purchase.

Every tap sets off a lightning-fast relay. When someone buys coffee with their Visa, a tiny "runner" races between the coffee shop's bank, Visa's network, and their bank—all in under a second. The catch? No money has actually moved yet. Here's what really happens behind that instant "Approved."

Laminar flow moves in smooth, parallel layers, while turbulent flow is chaotic

In laminar flow, particles that make up a fluid move in consistent paths that do not cross each other. Contrastingly, differences across the speed of these particles cause them to mix, creating turbulence when viscosity cannot suppress the differences.

Fire engines are among the most complex vehicles on the road

These vehicles are purpose-built to carry water, foam, hoses, ladders, and lifesaving equipment to a scene in minutes. This animated video pulls apart every system inside a pumper truck, showing exactly how the machinery that fights fires actually works.

An overview of Earth's atmospheric cells and how they distribute Earth's uneven heating

The Hadley, Ferrel, and Polar cells are circulation patterns that act like gears, moving warmer air from the equator to the poles. The rising and falling of air currents within these patterns creates semi-persistent regions of low and high pressure, which contribute to the formation of regional climates, such as tropical zones.

The deadliest aspect of volcanic eruptions is often not lava, but pyroclastic flows—avalanches of ash, gas, and rock that can move more than half the speed of sound.

How does your body turn food into energy?

Cells get energy via a process known as cellular respiration, which involves turning glucose into ATP or adenosine triphosphate. Breaking the phosphate bonds of ATP results in usable energy being released into cells, which can then use that energy to power biological processes. This 10-minute video explains how glucose turns into ATP, giving the body the energy it needs to survive.

Take a journey to the Earth's core

This animated video takes you on a journey through the different layers of the Earth's core, with insight into what makes up each shell. Earth's outer core, which is about 1,400 miles thick, is made up of liquid iron and nickel at a blistering...

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

The deadliest aspect of volcanic eruptions is often not lava, but pyroclastic flows—avalanches of ash, gas, and rock that can move more than half the speed of sound.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

Exploring the Larry Bird punch that almost changed March Madness

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak each year.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Hear about the 250-year history of the United States Postal Service, complete with some of its strangest deliveries, important innovations, and the figures that made it an American institution.

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.

Play the role of a student in a game where you try to navigate college and remain debt-free, selecting different income levels, high school experience, race, ethnicity, and more.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.