Skin
When you think of vital organs, you probably picture your heart, your brain, or your lungs. But there is a massive, incredibly complex organ that covers you from head to toe, holding everything else inside! Let us take a closer look at the science of your skin.
What is the Largest Organ in Your Entire Body?
Your skin! It makes up about 16 percent of your total body weight. It is a living, breathing shield that regulates your temperature and keeps out dangerous germs.
Dead skin cells! Humans shed millions of dead skin cells every single day. Your skin is constantly renewing itself from the inside out to keep your protective armour fresh.
Put Your Instincts to the Test
Think about what you already know about your body. Pick an answer for each question, then see if your instincts were right.
Completely dead cells! The top layer of your skin is dead, which is actually a great thing. It creates a tough, waterproof shield that protects the living cells underneath.
To cool your body down! When the water in your sweat turns into a gas (evaporates), it pulls heat away from your skin, acting like a built-in air conditioner.
A special pigment called melanin! Melanin acts like natural sunscreen, absorbing harmful rays from the sun to protect the delicate cells deep inside your body.
Understanding the Science
Let us peel back the layers and break down the amazing science of the integumentary system with Bill Nye the Science Guy.
Key Concepts
Epidermis
Tap to learn moreThe epidermis is the thin, tough outer layer of your skin. The very top is made of dead cells that constantly flake off, while the bottom of this layer is constantly dividing to make new ones to replace them.
Dermis
Tap to learn moreThe dermis is the thicker, living inner layer of your skin right beneath the epidermis. It is a busy place, packed with blood vessels, sensitive nerves, hair roots, and sweat glands.
Melanin
Tap to learn moreMelanin is a special pigment produced in the epidermis. It gives skin its colour and acts like a powerful shield, absorbing harmful ultraviolet rays from the sun to prevent damage to your DNA.
Sweat Glands
Tap to learn moreSweat glands are tiny coiled tubes in the dermis that release salty water onto the surface of your skin. As this water turns to vapour and evaporates, it carries body heat away into the air.
Sebaceous (Oil) Glands
Tap to learn moreThese tiny glands produce a natural oil called sebum. This oil constantly coats your skin and hair, keeping it soft, making it waterproof, and stopping it from drying out and cracking.
Goosebumps
Tap to learn moreTiny muscles attached to your hair follicles contract when you are cold, pulling the hairs straight up to form goosebumps. In furry animals, this traps a layer of warm air, but humans do not have enough hair for it to work very well!
Nerve Endings
Tap to learn moreMillions of tiny sensors called nerve endings live in your dermis and send messages up to your brain. They act like warning systems, allowing you to feel touch, pressure, heat, cold, and pain.
Fingerprints
Tap to learn moreFingerprints are tiny friction ridges on your hands and feet. They help you grip objects tightly, and because of how they form before you are born, no two people on Earth have the exact same pattern!
Try It: Interactive Skin Cross-Section
Take control of the environment! Adjust the "Temperature" and "Sunlight" sliders to watch how the layers of skin react. See sweat drops form to cool you down, and watch melanin darken to protect the cells from UV rays.
Apply Your Knowledge
Let us see if you can match the parts of your skin to the real-world technologies that do similar jobs.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real-World Challenge
Imagine you are a biomedical engineer designing a new spacesuit for astronauts. Based on the amazing functions of human skin, list three specific systems your spacesuit must have to keep the astronaut alive and comfortable in the harsh environment of space.
What Has Changed Since This Episode Aired
This episode first aired in the early 1990s. While the biology of our skin has not changed, medical science and our understanding of how to protect it have advanced incredibly!
Updated: Not quite! In the 1990s, sunscreens mostly only protected against "UVB" rays (the ones that cause immediate sunburns). Today, we know that "UVA" rays penetrate even deeper and cause long-term skin damage. Modern sunscreens are "Broad Spectrum", meaning they protect against both types of harmful rays. We also now have reef-safe sunscreens that protect delicate marine life when we swim in the ocean!
Updated: In the past, treating severe burns meant moving skin from one part of the body to another (a skin graft), which was painful and limited by how much healthy skin a person had. Today, scientists can take a few of a patient's own skin cells, grow them in a laboratory, and even use 3D bioprinters to print new, living sheets of skin to heal severe injuries!
Updated: Yes! We now know that your immune system is what makes tattoos permanent. When the needle puts ink into the dermis, white blood cells called "macrophages" rush over to eat the ink because they think it is an invading germ. When those immune cells eventually die, they pass the ink onto brand new macrophages, holding the art safely in place forever.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
Your score:
Reflection
Your skin works incredibly hard every single day to regulate your temperature, keep out germs, and let you feel the world. What are three things you can do to take better care of your largest organ?
Episode Discussion
Share your thoughts on this Bill Nye episode