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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

19. Stem Cells

Stem Cells


Stem Cells

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Hello everyone in this lesson. We are going to be talking about stem cells generally what they do and what the different types of stem cells are going to be okay. So we've all probably heard of stem cells at some point in our biological career, right stem cells are going to be cells that are responsible for providing a continuous supply of differentiated cells. Remember differentiated cells are going to be cells that have a particular function like skin cells are differentiated cells. The cells in your eye are differentiated cells. They have a particular function. Stem cells on the other hand, they are not going to be differentiated cells. They don't have a super specific function like being a cell in the retina of your eye. No stem cells are going to be the types of cells that are kind of going to be like blank slates and what they're going to be used for. Is there going to be this nice cell that can literally become any type of cell that the body needs and then it is going to divide and create new cells. This is how the body has a continuous supply of new cells to fix itself to grow or to repair damage or something like that. So they are self renewing which means their divisions replace themselves. So whenever you have a division, remember that you have the parent cell and then the parent cell is going to divide into two daughter cells. So the way that stem cells work is they're going to have one daughter cell remain a stem cell while the other daughter cell is going to become whatever type of differentiated cell the body needs. So it's self renewing. One stem cell is created and one differentiated cell is created from each stem cell. This way we don't run out of our very important stem cells. So stem cells are going to be present in most types of adult tissues but they're going to have very special locations, generally called niche locations. And these are just going to be locations throughout the body where the stem cells sit and divide into the different types of cells that the body needs. And generally in adults, stem cells are going to be utilized to repair damage to the body. So this is just an overview of generalized example, if this is a stem cell here, this is also the parent cell. Let's say that this cell goes through mitosis. Well remember they are self renewing, that means one of the daughter cells. This purple one is going to be a stem cell just like the parent cell and then this blue one is going to be the differentiated, oops differing she ate it. So, so this may be a skin cell or type of a kidney cell or whatever the body actually needs. That's going to be the blue one while the body still retains the same amount of stem cells because these are self renewing divisions. Okay, alright, so now let's go down and let's talk about the different types of stem cells, you probably have heard of different types of stem cells. There are many different classifications. So there are many different types of stem cells like I said, and let's start off with the most generalized types of stem cells and these are going to be embryonic stem cells. And these are going to be stem cells that are derived from the embryo, the developing embryo of the next generation of the next organism. Right. And generally we're going to say that embryonic stem cells are going to be pleurisy potent. So potency is telling us how much this stem cell can actually become. How many different types of differentiated cells can this particular stem cell become? If it's pleura potent, if it's toady potent, if it's multi potent, if it's a progenitor cell, these are going to be different levels of potency. Now, embryonic stem cells are generally going to be pluripotent stem cells meaning that they can differentiate into any cell type. Now be careful here, they can differentiate into any cell type in the body. And when I say in the body, I mean the body of the organism that is being created, the body of the embryo that is being made, that next organism that's being made. Pluripotent stem cells can be any specific cell type in the body of that organism. Now, I'm going to talk about another type of stem cell that you've probably heard before but it's not listed here. So there's also toti potent stem cells you will also commonly hear about. Toti potent stem cells, Tony potent stem cells are probably, you're really not going to work with these in types of research or anything like that, totally potent stem cells are going to be stem cells that can become any cell in the body or placenta. So literally anything. So Totie means total potent, so types of cells, it can literally become any type of cell in the body or the placenta of the developing organism. So totally potent stem cell is a great example of a total potent stem cell is going to be a zygote. A zygote is going to be that very first cell that is made by the fusion of egg and sperm and then that one cell literally becomes everything else. It is totally potent. It is a totally potent stem cell. These obviously are not really going to be used because they have to create the next organism. But pluripotent stem cell are very commonly used in experiments and stem cell experiments like that. So, I just wanted you to know that there are total potent stem cells but there are also pluripotent pluripotent stem cells plural means they can become into plural or many types of different stem cells but only in the body of the order. They can't become any outside things like the placenta, like Tony potent stem cells can become, Okay, so now let's move on to a different type of pluripotent induced pluripotent stem cells. These are going to be stem cells that are made into pluripotent stem cells artificially by our experimentation. These are going to be regular cells taken from adult tissues that are reprogrammed to become pluripotent stem cells and the way that scientists are going to do this as a very fancy special way. They're going to use all these different types of proteins to turn them back into pluripotent stem cells. This doesn't always work. It's not super efficient. Obviously researchers are still perfecting this mechanism but they have in fact done this. So what is this going to do? This is going to take a differentiated cell, reverse it, make it undifferentiated and turn it into a stem cell. This is very important because this can be utilized to make patient specific stem cells which they can use to repair the damage of an individual. Maybe they have some knee damage some joint damage. Maybe they can use those induced pluripotent stem cells to repair and re grow some of that tissue in that knee or that joint. That's the thought process behind these types of stem cells. Now, there are also progenitor cells. Progenitor cells are going to be stem cells that give rise only to a few different types of cells. They're not going to be as specialized as pluripotent and definitely not as specialized as Tony potent right Tony potent pluripotent can become almost anything progenitor cells. They're pretty specialized. They have the one thing that they make right? So these are going to be things like hematopoietic stem cells which are going to be stem cells that are found in your bone marrow. And these are only going to make blood cells. They don't make anything else. But they make all the different types of blood cells. So they're very specific. Right? And then we're going to have neuronal stem cells which are going to be utilized to replace your neurons throughout your life or grow neurons whenever you are developing. So again has a very specific job. It's very specialized. It doesn't make all those generalized cell types. So it's got a smaller niche. Now let's go down and I'm going to show you an example. Just a generalized example of how induced pluripotent stem cells actually come about. So let's say that these are our human somatic cells. And maybe these are going to be something like I don't know maybe these are skin cells. Maybe these are just normal skin cells that have already differentiated. They already have their job. Then the scientists are going to mix them with the specialized proteins that are going to reduce their specialization and gonna turn them back into stem cells. So I. P. S. Just stands for induced pluripotent stem cells and that's what they say right here. So basically now these cells are stem cells and they can be utilized to make different types of cells to regrow tissue or to repair damage. So maybe they become something for miso derm, endo dermarr, ectodermal. It really doesn't matter. We can make these stem cells to help repair some portion of an individual's body. Okay, everyone. So that was our lesson on stem cells. Now, let's go on to our next topic.

Pluripotent means…


Which of the following terms describes stem cells that can only give rise to certain types of cells?