What causes a Nosebleed?

Summary

Who Smarted? – “What Causes a Nosebleed?” (Nov 19, 2025)

Episode Overview

In this engaging and humorous episode, the Trusty Narrator finds himself in a spooky Transylvanian gift shop, where an accidental paper cut leads to an unexpected adventure with Valentina—a mysterious (possibly vampiric) shopkeeper. Together, they explore the science of blood and answer the central question: what causes a nosebleed? Along the way, they unravel the components of blood, why we bleed, and other fascinating facts about the human circulatory system, all while maintaining a light-hearted tone and playful banter fit for kids and families.

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Key Discussion Points and Insights

1. Blood Basics: What’s in Blood?

• Red Blood Cells: Carry oxygen throughout the body. Determine blood type (A, B, AB, or O, with positive or negative).
• White Blood Cells: Fight infections and help keep us healthy.

  “Do you know the very important job that white blood cells have?... If you said A, help fight infections, you’re right.” – Trusty Narrator (07:35)

• Platelets: Clump together to stop bleeding by forming clots.

  “Platelets are cell fragments that clump together to stop the bleeding when a cut occurs.” – Valentina (08:04)

• Plasma: Yellowish liquid part of blood, holds water, proteins, nutrients, and hormones.

  “It's also very important... mostly water, but it contains important proteins, nutrients, and hormones.” – Valentina (09:18)

2. Why Do We Bleed?

• Cuts and Blood Vessels: When skin is broken, blood escapes from vessels much like water from a punctured bag.

  “If you cut yourself, you break through layers of skin and you cut open blood vessels, too.” – Valentina (10:13)

• Superficial vs. Deeper Cuts: Shallow cuts may not bleed if only the outer skin (without blood vessels) is affected.

  “...your skin has many layers, and the outermost layer does not contain blood vessels. So if the cut isn’t very deep, you might not bleed at all.” – Valentina (14:29)

3. The Science of Nosebleeds (Main Theme)

• Why Do Nosebleeds Happen?
  • The lining inside your nose contains lots of tiny blood vessels close to the surface.
  • Two main causes:
    • Dry air dries and cracks the lining, causing vessels to break.
    • Nose picking irritates vessels, leading to bleeding.

  “The two most common reasons your nose might bleed are if the air is too dry and/or you pick your nose. Ew.” – Valentina (11:51)

• Other Causes: Strong chemicals (like ammonia) or blood-thinning medications can also trigger nosebleeds.
• Not Random: There are always causes behind a nosebleed; it’s not truly spontaneous.

4. Why Are Some Cuts Bloodless?

• Only deeper cuts that reach the layers containing blood vessels will bleed.
• Superficial scratches, or even punctures like a vampire bite or a cat scratch, might not bleed much if they miss blood vessels.

5. Bleeding—Where and Why?

• Eye’s Surface (Cornea): It doesn’t bleed—the cornea has no blood vessels, so nutrients and oxygen come from tears and “aqueous humor.”

  “The outermost surface of your eyeball is called the cornea. The cornea has no blood vessels and therefore cannot bleed.” – Valentina (15:50)

• Parts that Bleed Most: The head bleeds the most when cut, due to its dense network of blood vessels.

  “Which part of the human body tends to bleed the most if it becomes cut or wounded? ... If you said your head, you’re right.” – Valentina (17:24) “Because your brain is super hard working, it needs lots of oxygen to function. So a lot of blood is pumped up towards your head.” – Valentina (18:23)

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Notable Quotes & Memorable Moments

• Vampire Tease:

  “My name is Valentina, but I’m also a vampire. Very helpful person.” – Valentina (03:25)

• Blood Color Explained:

  “Blood gets its color from something called hemoglobin. It's a molecule that contains iron. The iron is what gives your blood its scrumptious red color.” – Valentina (08:51)

• Vampire Humor:

  “...puncture wound could be from a nail, a knife, or…or a tooth.” – Valentina (14:45)

• Blood Type Joke:

  “I'll take the fake meat cake one and this one that says always B positive. Wait, did I get blood on it? Oh, it’s just a picture of blood. Oh, I get it. B positive. Like one of the four main blood types. How fun.” – Trusty Narrator (19:23)

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Important Segments & Timestamps

• [01:44] – The narrator’s adventure begins in a Transylvanian gift shop.
• [03:28] – Introduction to Valentina, the vampire-esque shopkeeper.
• [05:15] – The science journey officially begins.
• [06:33] – “Museum of Blood”: exploring what’s in blood.
• [09:31] – Plasma’s role and what’s really in your blood.
• [10:13] – Why do we bleed? Blood vessels and cuts explained.
• [11:08] – What causes nosebleeds? Dry air and nose picking revealed.
• [12:57] – Why do some cuts not bleed? Layers of skin explained.
• [15:23] – Which body parts don’t bleed: the cornea.
• [16:40] – Which parts bleed most: the scalp and head.
• [19:02] – Wrap up with blood-type jokes and postcards.

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Tone and Style

The episode is kid-friendly, blending playful banter and gentle spookiness (appropriate for the vampire theme) with clear, scientific explanations. The co-hosts joke, tease, and quiz listeners throughout, using silly humor and lots of encouragement to keep the learning lighthearted and memorable.

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Summary

This episode of “Who Smarted?” transforms the mystery of nosebleeds into a fun, science-rich adventure. Listeners discover the layers of blood, why we sometimes bleed (or don’t), and what really causes those pesky nosebleeds (hint: it’s usually dry air or nose picking). More broadly, kids learn fascinating details about their own bodies, all while engaging with memorable, vampire-tinged humor and interactive quiz moments. Whether you’re a kid, parent, or teacher, you’ll finish the episode knowing exactly what to say next time someone gets a nosebleed—or wonders about the mysteries beneath their own skin!

Transcript

[Trusty Narrator]

Hey, smarty pants and smarty families. So today I was supposed to bring you the sad news that this would be the last day of our Special Happy Birthday. 50% off WhoSmarted plus subscription. But guess what? With Thanksgiving and Black Friday coming up, I just had to extend it another couple of weeks. So now you have until the end of November to sign up for WhoSmarted plus and get an entire year of smarting ad free, including a brand new subscriber only bonus episode every single week for just $19.98. That's right. For just $1.66 a month, you'll be supporting the show and giving the gift of smarting to the smartypants in your life just in time for the holidays. You can't even get a decent slice of pizza for $1.66. So what do you say? Go to our website, WhoSmarted.com and click Birthday Subscribe Today. That's WhoSmarted.com. click Birthday subscribe. This is only available on our [e-mail] you and I and all your friends at Whosmarted will be glad you did. And happy holidays. Hi. It's trusty. First, a big thank you to our subscribers. If you're not a subscriber, you can subscribe now, right on Apple Podcasts or on our website WhoSmarted.com youm'll get a free extra episode every week. Questions answered by me for you, the Smartypants and ad free listening, all for just a few dollars a month. Check it out now, right on Apple podcasts [e-mail] and now it's time for who's Smarty?

[Valentina]

Psst.

[Trusty Narrator]

Hey, Smartypants. Right now I am in a spooky gift shop in a spooky part of the world picking out a postcard to send my grandma. Let's see. Greetings from Transylvania. Boring. I'm having a blood sucking good time. That's a little gruesome for grandma. How about greetings from my cozy coffin? Cute, but no. As I'm sure some of you smarty pants have already guessed, I'm in Transylvania. The land of vampires, according to legend. But between you and I, we both know vampires don't really exist. Ooh, does that card have a meat cake on it? Oh, nope, just a regular cake. But also ouch. I grabbed the postcard so fast, I gave myself a nasty paper cut. Have you ever given yourself a paper cut, smarty pants? They're the worst. I should probably get a band aid. Maybe the woman behind the counter has One. Excuse me, I just gave myself a paper cut on one of your postcards. Any chance you have a band aid?

[Valentina]

A paper cut, a band aid? It must be my lucky day.

[Trusty Narrator]

Uh, excuse me.

[Valentina]

Oops. I meant what a terrible mishap. I'm sure I have a band aid in the back. Come with me and we'll go find the first aid kit.

[Trusty Narrator]

Um, you want me to come with you?

[Valentina]

What, are you afraid?

[Trusty Narrator]

No, it's just, you know, you're acting like a.

[Valentina]

Valentina.

[Trusty Narrator]

Huh.

[Valentina]

My name is Valentina, but I'm also a vampire. Very helpful person. I found the first aid kit. Let me see your verrry bloody thing. Actually, it's not too bad, but it's so beautifully bloody.

[Trusty Narrator]

Actually, it's just a tiny spot. Maybe I don't even need a band.

[Valentina]

There. All done. And what is your name again?

[Trusty Narrator]

I'm the trusty narrator from the Whosmarted podcast.

[Valentina]

Oh, is that the show where you teach the smartypants about fun things like blood?

[Trusty Narrator]

Hey, are you sure you're not a vampire?

[Valentina]

Who, me? No, I'm just a mild mannered gift shopkeeper with a thirst. I mean, fascination with blood.

[Trusty Narrator]

Right? That's not creepy at all. So, Valentina, if you know so much about blood, why do we bleed anyway? And what makes blood red? Oh, and what's the deal with nosebleeds? They seem so random. One minute you're walking down the street, when suddenly, bam. You got a gusher.

[Valentina]

Seems you're fascinated by the red stuff too. Come, follow me down this long, dark, cobweb filled hallway and I'll answer all your bloody quest questions.

[Trusty Narrator]

Oh boy. Smarty pants, get ready to join me and this woman who may or may not be a vampire, as we take a big bloody whiff of science and history on who's smarted.

[Whosmarted Theme Singer]

Who'S smarted, who's smart? Is it you? Is it me? Is it science or history? Listen up, everyone. We make smarting lots of fun. But who's smart?

[Trusty Narrator]

And who? Wow, this is some long hallway. Are we still in the gift shop?

[Valentina]

Okay, Mr. Narrator, before we get into the how and the why of bleeding, let's cover some blood basics. Humans are just full of blood. Your hearts pump blood throughout your body to keep you from being undead. I mean alive. Blood also provides your organs and tissues with nutrients and oxygen so they can function properly. But blood itself has many different parts to it.

[Trusty Narrator]

Parts? What do you mean parts? Isn't it just red liquid? Smarty pants, do you know about these blood parts?

[Valentina]

You have much to learn. Come, let us enter the museum of blood.

[Trusty Narrator]

Do most gift shops have a museum.

[Valentina]

Of blood in Transylvania? All shops have a museum of blood. As I was saying, many things make up your blood. First, you have red blood cells, which carry oxygen throughout your body.

[Whosmarted Theme Singer]

Oh.

[Valentina]

It's your red blood cells that also determine your blood type.

[Trusty Narrator]

Smarty pants. Do you know the four main blood types? There's A, B, A, B, and O. And they come in positive or negative. There's a lot to cover in blood types, so we'll probably make that a separate episode. All you need to know for now is that your blood type is inherited from your parents. And you need to know it in case you donate or have to get blood.

[Valentina]

I take all blood types.

[Trusty Narrator]

Right. Anyway, moving on. Next.

[Valentina]

You also have white blood cells.

[Trusty Narrator]

Smarty pants. Do you know the very important job that white blood cells have? Is it to A, fight infections, B, regulate body temperature, or C, clean the red blood cells? If you said A, help fight infections, you're right.

[Valentina]

Well done, smarty pants. Moving on. We have platelets.

[Trusty Narrator]

Yech. They look nothing like plates. More like spiders.

[Valentina]

Platelets are cell fragments that clump together to stop the bleeding when a cut occurs. Kind of like that delicious paper cut you just got.

[Trusty Narrator]

Did you just say delicious?

[Valentina]

Maybe.

[Trusty Narrator]

Anyway, is that what's happening under this band aid right now?

[Valentina]

Yes. The platelets are coming together to help stop the flow of blood. You're yummy. Warm, bright red blood. Speaking of bright red, you were wondering where blood gets its wonderful color? No.

[Trusty Narrator]

Yes. I'm also going to ignore that crazy outburst and evil laughing.

[Valentina]

Blood gets its color from something called hemoglobin. It's a molecule that contains iron. The iron is what gives your blood its scrumptious red color. If you step this way, you'll see the final component of blood.

[Trusty Narrator]

Ew. What's that yellow, watery liquid? Don't tell me that's in our blood.

[Valentina]

I know, I know. I prefer the red parts too. But yes, this yellowy, watery liquid is in your blood. It's also very important.

[Trusty Narrator]

What is it?

[Valentina]

Mostly water. But it contains important proteins, nutrients, and hormones.

[Trusty Narrator]

Smarty pants, what do you think this watery liquid in your blood is called? Is it A, magma, B, plasma, or C, omega? If you said B plasma. Nice. Wow, Valentina. I never realized there was so much stuff inside blood.

[Valentina]

It takes a village. Or in the case of blood, it takes cells, hormones, nutrients, molecules and proteins.

[Trusty Narrator]

Okay, now that we know what's in blood, we want to know, why do we bleed?

[Valentina]

Simple. If you cut Yourself, you break through layers of skin and you cut open blood vessels, too. Blood vessels are the tiny little tubes your blood flows through. When you have a cut, the blood spills out of those blood vessels through whatever opening was created. Like if you had a plastic bag full of water and you made a little incision in the bag with a knife, that water's gonna spill out.

[Trusty Narrator]

Okay, okay, that almost makes sense.

[Valentina]

Almost? What do you mean almost?

[Trusty Narrator]

Well, so called blood expert who does not identify as a vampire. What about nosebleeds? There's no cut. When a nosebleed happens, it just happens. How?

[Valentina]

Why.

[Trusty Narrator]

Why do noses just start spontaneously bleeding? Oh, spontaneous is a fancy word for unexpected.

[Valentina]

Oh, it's neither spontaneous nor unexpected. You see, the inside of your nose contains lots of teeny tiny blood vessels along the surface. There's two main causes that irritate those tiny vessels and cause nosebleeds.

[Trusty Narrator]

Smarty pants. Any idea what they are? Are nosebleeds caused by A, allergies and minty smells, B, dry air and nose picking, or C hot weather and prickly nose hair? The answer is B.

[Valentina]

The two most common reasons your nose might bleed are if the air is too dry and. Or you pick your nose. Ew. Both of these irritate your nose's blood vessels. But other things can cause a nosebleed, such as inhaling a strong chemical like ammonia or taking medications that thin your blood.

[Trusty Narrator]

So what you're saying is nosebleeds aren't random?

[Valentina]

No, there is always a cause. Just like delectable vapor guts.

[Trusty Narrator]

Okay, okay, relax. There's another scenario I'm curious about. One time, I was slicing vegetables when I accidentally cut myself with a kitchen knife. I yelled, ouch. But when I looked out at the cutting board, instead of seeing blood covered broccoli, there was no blood. There was definitely a cut in my skin. So how is it possible that no blood started gushing out?

[Valentina]

Excellent question. The answer is coming up right after.

[Trusty Narrator]

This quick break and a word from our sponsors. WhoSmarted is brought to you by Squarespace. Now, you know I'm good about creating new adventures and episodes of Whosmarted, but you don't know that I procrastinate on other stuff. Like a website for one of our new projects. Oops. When the website builder Squarespace reached out about sponsoring WhoSmarted, I decided to test it out. And now I feel silly for putting off building that website. Squarespace's blueprint AI thing literally built me a custom website in minutes. I just told it a few details about the project and boom, it generated everything. And everything you need is right there. I can schedule guest interviews, send email campaigns, even sell merch, all from one dashboard. Now it's your turn to stop procrastinating and start building. You can use Squarespace to launch that business site or any site that you've been dreaming about. But putting off today, there's no excuse anymore. Especially since you can head to squarespace.com smarted for a free trial. And when you're ready to launch, you can use Code smarted to save 10% on your first purchase of a website or domain. That's squarespace.com smarted code smarted. Now back to who's smarted. Ouch. I just nicked my finger with a knife. I better get a band aid only. Where's the blood? Why are some cuts bloodless?

[Valentina]

Well, you see, your skin has many layers, and the outermost layer does not contain blood vessels. So if the cut isn't very deep, you might not bleed at all.

[Trusty Narrator]

Whoa. Did you know that, smarty pants? That's so cool.

[Valentina]

Same goes for a puncture wound. A puncture wound could be from a nail, a knife, or. Or a tooth.

[Trusty Narrator]

A tooth? Oh, you mean like from a vampire?

[Valentina]

Or a cat or dog Or a teething little brother. Puncture wounds tend to be straight and long, and so it may not cause as much damage to the blood vessels, possibly resulting in no bleeding.

[Trusty Narrator]

Wow. Are there any parts of the body that can't ever bleed?

[Valentina]

Nothing. Aside from the obvious ones like hair, teeth and nails, there is one part of your body that sadly doesn't bleed.

[Trusty Narrator]

What do you think it is, smarty pants? Is it, A, the surface of your eye, B, the surface of your brain, or C, the skin of your elbows? It's a tricky one, smarty pants, but the answer is, A.

[Valentina]

The outermost surface of your eyeball is called the cornea. The cornea has no blood vessels and therefore cannot bleed.

[Trusty Narrator]

But you said blood carries oxygen and nutrients to all the parts of our body. So does that mean our eyes are not oxygenated or nutritious?

[Valentina]

Oh, they're nutritious alright. Just not very delicious.

[Trusty Narrator]

Huh?

[Valentina]

Sorry, I'm just hungry. You see, instead of blood bringing oxygen and nutrients to your cornea, it's actually your tears, along with a watery substance behind the cornea called aqueous humor, that supply the cornea with its nutrients and oxygen.

[Trusty Narrator]

Interesting. So if the cornea is the part of the body that doesn't bleed at all, is there a part of the body that bleeds the most?

[Valentina]

Indeed. There is. There is a very special, very important part of your body practically bursting at the seams with rich, red, warm, gushing blood. Sorry, I got a little carried away.

[Trusty Narrator]

I'll say. But before you say the answer, let's see if the smarty pants can get it. Which part of the human body tends to bleed the most if it becomes cut or wounded? Is it your stomach, your head, or your appendix? Which do you think?

[Valentina]

If you said your head, you're right.

[Trusty Narrator]

Good job if you got that. But why would your head bleed the most? I figured it would be your chest or stomach near your heart.

[Valentina]

That makes sense. Bull. It's your head. And the reason is simple. As you've learned, bleeding occurs when blood vessels break. And your head contains lots of blood vessels. More blood vessels means more blood loss from head injuries.

[Trusty Narrator]

Ah, that makes sense.

[Valentina]

These injuries can include deep ones where there may be bleeding on or around the brain. Or more superficial head injuries like a cut to your scalp, because the skin of the scalp also contains lots and lots of blood vessels.

[Trusty Narrator]

Is there a reason your head has so many blood vessels in it?

[Valentina]

Absolutely. As you also learned earlier, blood carries oxygen to various body parts. Because your brain is super hard working, it needs lots of oxygen to function. So a lot of blood is pumped up towards your head.

[Trusty Narrator]

You know, Valentina, if you told me this morning that picking up a postcard would result in a paper cut, which would result in learning tons of cool facts about blood and bleeding, I'd say you had a very active imagination. Like the kind that believes in vampires.

[Valentina]

Well, you know how it is. Transylvania is an aim place full of many mysteries. It's easy to get caught up in strange myths and legends. So have you decided which postcard to buy?

[Trusty Narrator]

Yes. I'll take the fake meat cake one and this one that says always be positive. Wait, did I get blood on it? Oh, it's just a picture of blood. Oh, I get it. B positive. Like one of the four main blood types. How fun. Ring me up. Valentina. Valentina.

[Valentina]

Sorry, trusty, the sun will be up soon. I got a fly. My associate will take care of you. Nice meeting you.

[Trusty Narrator]

A big shout out to Grace in Aurora, Colorado. Thanks for smarting with us. We love hearing how much fun you have listening to who Smarted. Because you enjoy all the silly stuff we do while helping you learn lots of new things. That's what we do, Grace this episode. Blood was written by Phil Plasma Jeremy and voiced by Charlotte Coagulate Cohn and Jerry Colbert. Technical direction and sound design by Josh Hemoglobin Hahn. Our associate producer is Max Antibody Kamasky. The theme song is by Brian Be Positive Suarez with lyrics written and performed by Adam Type O Negative Davis. Who Smarted was created and produced by Adam, Tex Davis and Jerry Colbert. This has been an Atomic Entertainment production.

[Whosmarted Theme Singer]

Who Smarted.