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skip navigation links Student Activities 1 - Cancer and the Cell Cycle - return to student activities home, student by a school bus Video Animation 1 The rate and timing of cell division in your body are normally very precisely regulated. Late in the development of cancer, some cells may gain the ability to move into. The CancerQuest Documentary is an 11 min video-animation that describes Click on the links below to view the individual animations. Normal Control of Cell Division The Tumor Biology animation / video series is designed to provide an overview of normal and cancer cell biology, tumor biology, and cancer treatment. Life is based on the ability of cells to reproduce, or make copies of themselves. This is done by a process called cell division = one cell divides.
And I want to make that point very clear. Now, you're saying, hey, Sal, billion new cells a day? That must mean like every cell in my body has created, well that just gives you an idea of how many cells we have. We actually have on the order of, and you know it's obviously not an exact number, but actually in the human body, there's on the order of trillion cells. And if you look at it that way, you say on average, one thousandth of your cells replicate each day, but the reality is some cells don't replicate that frequently at all and some cells replicate much more frequently.
Just to take a little side note here, this gives you an appreciation, I think, for the complexity of the human body. I mean we think of our own world economy and world society as so complex, it's made up of 6 billion humans. We're made up of trillion cells. Let me rewrite trillion in billions. And each one of thosebillion cells are these huge-- I know I shouldn't use the word huge-- but they're these complex ecosystems in and of themselves with their nucleuses. And we'll talk about all the different organelles they have, and we talked about cellular replication, DNA replication and how the cell replicates.
So these things aren't jokes and they have all of these complex membranes that take things into them.
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They are creatures to themselves, but they live in this complex environment or society that is each of us. So that's just a side note just to appreciate how large and how complex we are. But you can imagine, and this is how I got off on this tangent, if we're making on the order of billion new cells every day, you're going to have a lot of mutations, and maybe some of the mutations, you know I said some of them don't do anything. Some of them, the cell recognizes that the cell is just going to be kind of dead weight so the cell kind of eliminates itself.
But every now and then, you have mutations where the cell doesn't eliminate itself and it also deforms the cell.
So when you have that, let's say I have some cell here. I have some cell and it's got some mutation. I'll do that mutation with a little x right here. That's in its DNA. Maybe it's got a couple of mutations. So one of the mutations keeps it from experiencing apoptosis, or destroying itself, and maybe one of the mutations makes it replicate a little bit faster than its neighbors.
So this cell, through mitosis, it makes a bunch of copies of itself or a ton of copies of itself. And this kind of body of cells that essentially has a defect, they're all from one original cell that kept duplicating and then those duplicating, but all these are defective cells. If you were to look at them compared to the tissue around it, it would look abnormal in some way. Maybe it wouldn't function properly. This is called a neoplasm. Now, a lot of neoplasms, well they don't have to form a body like this.
Sometimes they might somehow circulate in the body, but most of the time they form this kind of big lump. And if they get large enough, they're noticeable. And that's when we call it a tumor. So if this is actually a lump of kind of differentiated tissue that's definitely abnormal, that's what you call a tumor. So the term neoplasm and tumor are often used interchangeably. Tumor is the word we use more in our everyday vocabulary. Now, if this lump just kind of grows to a certain size, it's just there, it doesn't really do anything dangerous, it's not replicating out of control.
I guess it's not replicating a lot faster than its neighboring cells and it's just hanging out, maybe growing a little bit, but not in any significant way harming our environment, we call that a benign tumor or a benign neoplasm. And benign essentially means harmless. That means that's good. You want to hear that. If you got a lump-- God forbid you have a lump either way-- but if you do and it's a benign tumor, that means that lump, it can kind of stick around, no damage done.
But if these DNA mutations, and maybe some of these are, it is benign, but maybe one of the benign ones has another mutation in it that starts making it grow like crazy.How Cancer Develops & Mutation
And not only does it grow like crazy, but it becomes invasive. And invasive means that it doesn't care what's going on around it. It just wants to infiltrate everything. So let's say that guy grows like crazy. And he starts infiltrating other tissue, so he's invasive. So super growth, he's invasive. So he doesn't care what's going on. He's all of a sudden turned into some type of a cellular psychopath. And even worse, his descendants, it's not just one cell anymore. He just keeps duplicating and passing on this kind of broken genetic information that makes it want to replicate.
And then maybe there could be more and more things that break down in its I guess offspring or the DNA that comes from its replications. And actually, that's a good likelihood, because the same parts of its DNA that broke down, some of the DNA that broke down in this guy, some of the mutations might have actually hurt the DNA replication scheme, so that mutations become more frequent.
So more frequent mutations. So as these replicate, more and more mutations appear, and then maybe eventually one of the mutations appears that allows these cells to break off and then travel to other parts of the body. And then those parts of the body start to take over and start taking over all of the cells. And this process is called the cell has-- this is one of the hardest words for me to say, something wrong with my brain-- but the cell has metastasized.
You might have heard the word metastasis, and that's just the notion of these run amok cells all of a sudden being able to travel to different parts of the body.
And I think you guys know what we call these cells. These cells that aren't respecting their cellular neighborhood. They're growing like crazy. They don't experience that contact inhibition. It is growing around a blood vessel, and you can see its three-dimensional shape as the microscope focuses up and down through it. This small tumor still does not need to attract new blood vessels to support its growth, because the blood vessel that it surrounds can support its growth at this size.
Attracting blood vessels QuickTime RealVideo: This small melanoma cancer is beginning to show signs of blood vessel activity inside it, and these might be 'angiogenic' new blood vessels. New blood vessels liver QuickTime RealVideo: By this stage, the tumor needs to continuously attract new vessels to keep on growing.
The normal liver tissue lighter color shows normal, healthy blood flow, and the tumor darker color shows new, angiogenic blood vessels with irregular shapes and blood flow, especially visible in the higher magnification clip.
New blood vessels body cavity QuickTime RealVideo: The black portion is the tumor and shows abnormal 'angiogenic' blood vessels, while the normal tissue lighter color has more normal blood flow. Continuous angiogenesis QuickTime RealVideo: It has attracted new blood vessels to grow up to it from the normal muscle tissue below.
When tumors get to be this size, they need continuous angiogenesis to keep on growing, otherwise their growth will stop. Normal, healthy blood vessels QuickTime RealVideo: The red-filled vessels are blood vessels, and the clear vessel to the right of a large blood vessel is a lymph vessel.