Curious Kids: why dont burns bleed?  02/19/2020 01:29:00   Theresa Larkin

Why dont burns bleed?  from the year three and four students at Islington Public School in NSW

Hello year three and four students  thanks for your excellent question!

To understand burns, we need to understand some things about the skin. Did you know your skin is made up of three different layers?

You might have heard of burns being called first-degree, second-degree or third-degree burns.

This tells us how many layers of skin are affected and how deep the burn is.

First-degree burns

A first-degree burn affects just the outer layer of the skin, which is called the epidermis.

The epidermis protects the inside of our body, including our muscles, bones and organs.

It stops the suns harmful rays, sharp objects and water from getting through and damaging the inside of our body.

Read more: Curious Kids: how do wounds heal?

Could you imagine if we didnt have a waterproof outer layer? You would fill with water and burst the next time you hopped in the bath!

When we have a first-degree burn, this affects just the outer layer of skin.

A first-degree burn, such as sunburn, is red, warm and painful to touch because the cells have been damaged.

Our skin protects us from the suns harmful rays, but dont forget the sunscreen so you dont get burnt! Shutterstock

So why doesnt a first-degree burn bleed? Because there actually isnt any blood travelling in the epidermis.

The blood vessels, which carry blood around our body, are in the next layer down.

This second layer is called the dermis.

Second-degree burns

A second-degree burn affects the outer two layers of the skin: that is the epidermis and the dermis.

The dermis has blood vessels that carry our blood around our body.

The epidermis is the top layer of the skin. The dermis is the second layer. Shutterstock

Now, you might think that because of the blood vessels in the dermis, a second-degree burn would bleed.

If you cut yourself into the dermis, say, with a deep paper cut, it might bleed.

The difference with a burn is the heat actually stops the blood from flowing.

A small bit of blood may ooze out at first, but it wont actually bleed much.

Read more: I've always wondered: why do our veins look blue when our blood is red?

The dermis also has nerves that make us feel pain if theyre damaged.

A second-degree burn is the most painful burn because it damages the nerves of the skin.

Third degree burns

The third and deepest layer of our skin is called the hypodermis. This is mostly fat, but there are also blood vessels and nerves in this layer.

The veins that you can see on the back of peoples hands are in the hypodermis layer of the skin.

A third-degree burn affects all three layers of skin. This is very deep and will need medical treatment.

Read more: Curious Kids: why do we get bruises?

A third-degree burn doesnt just damage cells like first-degree and second-degree burns, it actually kills them. The redness of sunburn, and even blisters, will gradually get better and return to normal. But dead cells cannot repair.

A third-degree burn also doesnt bleed because it completely destroys the blood vessels and the heat stops the blood from flowing.

Even though a third-degree burn causes the most damage, it is actually not painful at that location because it has completely killed the nerves.

Think of a jacket

Our skin is like our own three-layered waterproof, padded jacket.

Your skin is like a jacket with three layers. Shutterstock

The outer layer (epidermis) is thin and protects against water.

The middle layer (dermis) is the material and threading holding the jacket together.

The deepest layer (hypodermis) is thick and padded to keep us warm just like our fat.

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