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  • Voiceover: When most people hear the word cancer,

  • they usually think of a tumor,

  • so they think of a group of cells

  • that are dividing really rapidly

  • that eventually form a mass.

  • And you can see that mass.

  • You can point to it and say,

  • "That's the source of our problem.

  • "We need to get rid of it right away,

  • "either with surgery or with medicine."

  • I think what makes leukemia harder to understand

  • and harder to visualize than other types of cancers

  • is the fact that with leukemia you don't necessarily

  • see a tumor, and that's because

  • leukemia is a cancer of the blood.

  • Specifically, it's a cancer of blood cells.

  • So, what are these blood cells that I'm talking about?

  • Well, let's draw a blood vessel,

  • which is where all of the blood is contained.

  • When most people think of blood,

  • they think of a liquid, so that's what I am shading in,

  • the liquid part of the blood.

  • But blood has lots of cells in it too.

  • So, for one, it has these cells called red blood cells,

  • and hopefully you can see that,

  • which are really important for carrying oxygen

  • and oxygen is required by all of the organs in our body,

  • everything from your brain to your muscles requires oxygen.

  • Then there are these cells that are called platelets,

  • which actually aren't cells at all.

  • They are little chunks or fragments of cells

  • that form blood clots to help stop bleeding.

  • Then you have these guys.

  • There are several different types of white blood cells,

  • which is what our body uses to fight off infection.

  • So, these are the guys that protect us from bacteria

  • and viruses and parasites.

  • So, these cells are found in the blood.

  • That's why they are called blood cells.

  • But they are actually not made in the blood.

  • They are made inside the bone.

  • So, I'm going to draw a bone.

  • If you were to look inside the bone,

  • so if you were to take a slice of bone like this

  • and you were to look at it,

  • so this is your eye right here looking inside the bone,

  • you would see something like this.

  • You would see that on the outside of the bone

  • is this hard part that we all know about,

  • but you would see that bone isn't solid all throughout.

  • There's actually this hollow cavity in the center of the bone,

  • and that hollow cavity is filled with his red, spongy tissue.

  • That red, spongy tissue is called bone marrow,

  • and bone marrow is where all of these

  • different blood cells are made.

  • So, I'm going to clear that out so that we can see

  • what bone marrow looks like

  • and what's going on inside bone marrow.

  • If you looked inside, you'd see red blood cells being made,

  • you'd see some cells making platelets,

  • and you'd see white blood cells being made, right?

  • And this is normal.

  • This is all completely normal.

  • But in leukemia, one of these cells,

  • it could be a red blood cell,

  • a platelet, or a white blood cell,

  • starts multiplying really rapidly and out of control

  • and it starts overtaking the bone marrow,

  • kind of like this.

  • And that's a problem for two reasons.

  • Firstly, this cell that's dividing really rapidly,

  • this leukemia cell, doesn't serve any function

  • like a normal blood cell does.

  • So, it doesn't carry oxygen.

  • It doesn't fight off infection or help make blood clots.

  • It kind of does nothing.

  • It's kind of a waste of space,

  • and that's a problem because we don't want

  • to use any of our body's energy making cells

  • that don't help the body, right?

  • Secondly, it is a problem because if any one cell

  • starts dividing really rapidly

  • and taking up a lot of space inside the bone marrow,

  • that leaves behind very little space

  • and very little food for the other cells to grow.

  • So, because of this, the bone marrow

  • isn't able to make as many of those

  • other normal, healthy blood cells.

  • And if it can't make them,

  • then it can't supply them into the blood,

  • and that's the problem you see with leukemia,

  • where you start seeing fewer red blood cells in the blood,

  • that's those guys, and fewer platelets

  • and fewer white blood cells in the blood.

  • Then, eventually, when the leukemia cells

  • run out of space to grow inside the bone marrow,

  • they leak into the blood.

  • So, you start to see leukemia cells in the blood,

  • kind of like that,

  • and actually this picture right here

  • explains almost all of the symptoms

  • that you see in leukemia.

  • So, let's make some room to talk about

  • the symptoms of leukemia.

  • Okay, so firstly we said we see a decrease

  • in the number of red blood cells, right,

  • which I'm just going to abbreviate it

  • as RBCs for red blood cells.

  • Since red blood cells carry oxygen,

  • this leads to symptoms like weakness and tiredness

  • and fatigue, and the fatigue is from

  • the brain not getting enough oxygen.

  • And the body compensates for this

  • by starting to breathe more quickly.

  • So, the patient starts to experience

  • some shortness of breath.

  • And because red blood cells give the blood its red color,

  • the patient starts looking paler

  • when they have fewer red blood cells.

  • We also said that we see a decrease

  • in the number of platelets in leukemia.

  • So, if the patient starts bleeding for whatever reason,

  • they don't have enough platelets around

  • to form that blood clot that stops the bleeding.

  • So, they experience prolonged bleeding

  • and they also see easy bruising.

  • Okay.

  • And finally, we said that there is fewer white blood cells,

  • which I'm just going to abbreviate as WBCs, right.

  • And since white blood cells help fight off infection,

  • this leads to more frequent infections,

  • an increased number of infections,

  • or increased susceptibility to infections.

  • These cells, these leukemia cells,

  • that are really rapidly dividing,

  • take up a lot of the body's energy.

  • And because of that, you see symptoms such as

  • weakness and symptoms such as significant weight loss,

  • which are things that you see in lots of other cancers

  • because you also have rapidly dividing cells in other cancers.

  • And then, finally, the leukemia cells start to grow

  • into the wall of the bone,

  • and if you have ever had a bone fracture or bone infection,

  • you know that the wall of the bone

  • has lots of very sensitive sensory nerves in it,

  • and because of that, the patients with leukemia

  • start experiencing bone pain,

  • and that's not pain in just one bone,

  • it's pain throughout the bones of the body.

  • So, it's more generalized bone pain.

  • So, if a patient starts showing

  • signs and symptoms of leukemia,

  • a doctor will often start off by getting a blood test,

  • and if they get a blood test,

  • the first thing that you will see is this picture over here.

  • You'll see fewer of the healhy, normal cells

  • and you may even see the leukemia cells in the blood, right?

  • So, that would lead to the suspicion

  • that maybe the patient has leukemia,

  • and that suspicion can be confirmed

  • by actually looking inside the bone marrow,

  • and that's this.

  • I'm just drawing in the cavity inside the bone.

  • And you can look inside the bone marrow

  • by actually sticking a long needle inside the bone

  • and drawing out some fluid and then looking

  • at the stuff under the microscope,

  • and that's actually called a bone marrow aspiration.

  • So, in a nutshell, this is what leukemia is all about.

Voiceover: When most people hear the word cancer,

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白血病とは?| 血液系の病気|血液系の病気|白血病とは? (What is leukemia? | Hematologic System Diseases |)

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    Amy.Lin に公開 2021 年 01 月 14 日
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