Organogenesis and Neurulation

by Jason Amores Sumpter
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Now, after those germ layers have formed, we can begin organo Genesis or the process of organ and tissue development. And you might remember that those me the method ERM was made up of those two pockets. What we call those so mites those air pairs of miss a dermal tissue and he sells position in the, um in the so so might determines what it will turn into. So let's imagine that, uh, here is our so might and it's made up of a bunch of little individual cells again, this is just for the purposes of example. So depending on where the cell is located in the so might, it'll turn into different things. It'll actually break away in groups and migrate and form different things. So this cell might form, Let's say, cardiac muscle like we see here and maybe these cells the cell breaks away informs, Ah, skeletal muscle. So it's the actual physical position of the cell in the so mate that determines what it will develop into. And I'm sure you have some pretty good guesses as to how and why that can happen. Based on what we've already learned about development, concentration, radiance, and chemical signals. Now the museum layer develops into many different things we can see here, including cardiac muscle, skeletal muscle tube, you'll cells of the kidney, um, red blood cells and smooth muscle cells like those around the intestine. Now, in addition, to organize Genesis, there's another really important process that occurs an animal development. And this is no relation, which is the actual formation of nervous tissue from the primary germ layers. So a couple points of terminology here we have the note accord, which you can see here in the picture. This structure, um, on a fire scroll down a little so you can see the other images. The Noto cord is also present here and here, and it is labeled in this last image here. So what is the note accord? The note accord is kind of like a primitive backbone that develops in core dates, which is a a big class of types of animals, and in some animals it actually develops into the vertebrae of the spine. But in many animals, it's actually just a transient structure. It forms during development, and then it goes away at some point, and that's totally normal, part of the process, and it's because of that link to evolution. That close link that development has toe evolution. Now, in addition to the note, accord should be aware of the neural tube, which is a hollow structure that eventually will form the brain and spinal cord. The neural tube forms in kind of an interesting way. We have this neural plate, as it's called, and it basically, as you can see here it folds in on itself and seals the Ecto Durm. There's actor Derma on this side. This is also Ecto Durham. It seals the Ecto Durham together. So let me get rid of some of these eras just so this becomes a little more clear so you can see the ectodermal are the neural plate folds in on itself and then eventually boom. We have the actor Durham fuse. And again this neural tube structure that you see here will form the brain and spinal cord. In fact, it swells in certain places to form the embryonic brains. It'll swell and form little bulges that actually become embryonic brain structures. So the Meso Durham cells, uh, that formed the node accord actually are the same cells that induce. Remember, induction. Induce the ectodermal cells to furrow or form this, uh, form this fold and then fused together. Thio form the neural tube, the neural folds that surround the neural groove, um, actually give rise to the central nervous system. Now the last thing we need to talk about is sell determination, which is that irreversible commitment of a cell to a pick particular developmental path, which results in a specific cell type. We've talked about this. It happens through the process of differentiation. But what we haven't talked about is how differentiation is actually a gradual process. Sell a can give rise to Selby or sell C. Selby is capable of giving rise to sell D and sell E and sell. C can give rise to sell e or F, so differentiation occurs in stages to get from sell a to, let's say, sell F one. The cell has to go through that intermediary phase of being cell C, and at that point it's fate. As becoming cell F is still not sealed, It could also become sell e. It has options, so differentiation is a gradual process. However, once the cell is committed to a particular path. It's Fate is sealed. It's destiny. ISS sewed in the stars, and it is going to become differentiated to that particular type of cell. All right, that's all I have for this lesson. See you guys next time.