 In humans after fertilization, the baby keeps growing inside the mother's womb for about nine months. So as the baby grows, its energy demands, its nutrition demands keep on increasing. Where does it get it from? Well, it has to get it from the mother. But how does mother keep up with all the required nutrition for it? And similarly, the baby has to get rid of the waste products that it produces. So how does the mother ensure all of that? Well, to take care of all of this, a very specialized tissue gets generated. And that tissue is called the placenta, as you can see over here. So in this video, let's look at placenta in a little bit more detail and see how it nourishes the baby. So the placenta is a very special tissue. It's a disc-shaped tissue. It doesn't look like disc from this angle, but let me show you the image of an actual placenta. And you can kind of see it is disc-shaped. This is the same cord that is coming out of the placenta, as you can see over here. This is, you may be familiar with this, it's the umbilical cord. It's the one that connects to the belly button eventually. And of course, placenta, this is not really black. I have made it black and white because I don't like to see blood a lot. So anyways, it's a specialized disc-shaped structure. If we need to understand the structure of it, we may have to zoom in a little bit. So let me zoom in. Here it is, a small portion of the placenta zoomed in. You can now see some of the blood vessels over here, right? So this is the blood vessel from the mother. It's coming from the mother. So this is the mother's blood vessels and this is the blood vessels of the baby, which eventually goes into the umbilical cord. And so the specialty of placenta is that it contains both the mother's and the baby's blood vessels, meaning it contains both the cells of the mother's and the baby's. In other words, it contains both the DNA of the mother's and the baby's. That's the specialty of placenta. So let's see how the placenta helps baby get everything. So let's zoom in a little bit further. So if I would take a small section of that and zoom in, all right. Now we can see it better. So over here, like I said, these are the maternal blood vessels. So let me write that down. So this is the mother's blood vessels. Mother's blood vessels. I'm just gonna be V for blood vessels. What do they do? Well, you can see from the blood vessels, you have tiny vessels coming out and they eventually end over here. They open, not end, sorry, they open into this region, right? Into this region. So what they do is that they basically start putting the blood into the region. That's what the mother's blood vessels do. They fill this entire region up with her blood, right? This whole region gets filled with the mother's blood. So this is where you'll have, let me write that as well. This is where you'll have, this whole region contains mother's blood. So this will be the mother's blood that fills up this entire space. This whole thing is filled with mother's blood. And then these are the baby's blood vessels. So these, let me write that in blue. These represent the baby's blood vessels. Baby's blood vessels. And so how does the baby get its nutrition? Well, we can see all the deoxynated blood coming over here. This is all the deoxynated blood that the heart is pumping away. The baby's heart is pumping it away from its body. All the deoxynated blood which contains carbon dioxide, maybe it also contains all the waste products. So all of that comes over here and then it comes very close to the maternal blood. As you can see, these blood vessels eventually become very thin. They become capillaries and they come very close to the maternal blood. They don't come in contact with that. You can see there are structures over here to prevent the contact. There is no contact, but they come close. They come so close that diffusion starts happening. And so over here, what you will now find is that all that waste product, all that carbon dioxide gets diffused out. All that waste product gets diffused out. All of that, okay? All of that waste product gets diffused out. And all the oxygen starts getting diffused in. All the glucose and the nutrients start getting diffused in. And as a result of that, the deoxynated blood gets converted to oxygenated blood. The maternal blood oxygenates the baby's blood by diffusion. And now we have this rich oxygenated blood full of nutrients. And that blood is now carried by this vessel all the way to the baby's heart. And then the baby's heart can now start circulating that for the entire baby, the entire body. And then the cycle repeats. All the deoxynated blood is again pumped out of the umbilical cord to the placenta, gets deoxynated, and the cycle repeats. And so to increase the amount of exchange that can happen, to increase the area over here, we have these finger-like structures. And these finger-like structures are what we call the villi. You may have heard of this. In our intestines also we have villi. Again, the whole idea is to increase the surface area. The more surface area you have, the more chances of exchange happening. And as a result, the faster this whole process becomes. Now, one side note before we continue, an interesting side note. If you observe carefully, you can see the blood vessel that carries the blood away from the heart. This one, the blue one which I've shown over here. That's carrying the blood away from the heart. That blood vessel is usually what we call the arteries. Arteries are the one that carries the blood away from the heart, right? But notice the artery over here is carrying deoxynated blood. Mostly we like to think that arteries carry oxygenated blood. But in umbilical cord, the arteries carry deoxynated blood. And then the blood gets oxygenated. And then it flows back to the heart. And so the veins in the umbilical cord carry the oxygenated blood. Just like in our pulmonary system, just like in the system where exchange happens in our lungs, they're also the same thing happens. The arteries carry the oxygenated blood, deoxynated blood, sorry, and the veins carry the oxygenated blood. So the placenta kind of also plays the role of the lungs, because the baby's lungs are not fully developed over here. And now this blood which is getting more deoxynated, which is getting all the waste products from the baby, this blood will be continuously recycled. So this blood will be taken up by the mother's blood vessels. And that blood will now go for all the filtration process, for all the oxygenation process. And at the same time, fresh new blood will keep on filling this pool. So the pool of the blood will always be continuously recycled. We want to make sure this is always rich in oxygen, always rich in all the nutrition. And so our baby keeps growing this way for about nine months in the mother's belly, getting all the nutrition, all the oxygen that it needs from the placenta. And finally when it's ready, you'll usually see that the head will be positioned this way to come out first, usually at least, for normal deliveries at least. And then the uterus will start giving its rhythmic contraction, meaning the top part will contract. And at the same time, the bottom part will start relaxing. And as a result, the baby's head will get pushed out of the vagina. And so the baby's head comes out first, and then the baby's body comes out, and then doctors usually cut the umbilical cord and the baby is out. But to end the delivery, you know what happens finally? The placenta is shed out. That's the end of delivery. The placenta is not near anymore once the baby is out, right? So the delivery concludes with the shedding of placenta. The placenta finally comes out of the vagina. And so long story short, placenta is a special disc-shaped tissue which contains both the blood vessels of the mother and the blood vessels of the baby. It's responsible for nourishing the baby for the entire nine months, providing it with all the oxygen, the nutrition, and also removal of all the unwanted stuff, like carbon dioxide, the waste products from the baby's body. And how does it work? Well, the mother's blood vessels continuously keep pouring in fresh, oxygenated blood with all the goodies, all the nutrients in this particular space, which we can say is the mother's blood pool. And the oxygen and all the nutrients from that gets diffused into the baby's blood vessels. And that's how the baby gets all the oxygen and nutrients. At the same time, all the unwanted stuff gets diffused in that same blood from the baby's blood vessels. That's how the baby gets rid of all the unwanted stuff. The finger-like projections, which are called villi, increase the surface area to increase the amount of exchange that happens. And finally, the mother's blood is continuously recycled, getting rid of all the deoxygenated blood and resupplying it with all the oxygenated blood.