 Hi everybody, Dr. O. In this video, let's talk about sperm production. So you see here, we're looking at, we're looking inside one of your seminephorous tubules. So let's talk about the cells involved first, and we'll talk about the production of sperm. So the two key cell types we're going to look at here are going to be your sertoli cells. They are going to be a type of nerve cell that are going to help mature and produce sperm. The other name for them is sustentacular cells, as you can see here. So these are going to be the cells that produce signaling molecules that lead to, they promote sperm production and they can even decide if sperm live or die. So those are going to be the cells primarily responsible for sperm production. Sertoli cells or NERS cells are the terms that I use. Then we also are going to have, here at the bottom, the interstitial cells, or when I was in school, they were called the interstitial cells of lydig. So these are going to be the cells that produce the androgens, your male sex hormones, primarily testosterone. There are other ones like dihydrotestosterone, but testosterone is the primary androgen. So as your key cell types, we need the testosterone to keep the male reproductive system functioning, and we need sperm. So that's your sertoli cells or your NERS cells, and your interstitial cells, also known as lydig cells. Now let's look at the actual production of sperm. So you're going to see a couple words here, students get confused by, at the top we have spermatogenesis, and then near the bottom we have spermogenesis. Those are two different terms, so I'll try to clear that up. So spermatogenesis starts with the spermatogonium, that's the fancy term for the male stem cell that becomes your, the sperm. And then these cells are going to undergo mitosis, where this one spermatogonium is going to produce two, sorry, primary spermatocytes, and you'll notice this like other stem cells, that one of those two cells goes back and becomes a stem cell. So you're going to have a seemingly endless supply of sperm cell as long as this process occurs. And this is going to start at puberty, and it's going to continue on until sperm production would end, which really would never happen. All right, so the spermatogonium undergoes mitosis to become a primary spermatocyte. So what does this two end mean? This means these cells are diploid or diploid. They have two sets of chromosomes, which you want for all your somatic or body cells, but you don't want it for your sex cells. So we'll see, then these two, then this primary spermatocyte is going to undergo meiosis to become two secondary spermatocytes. Now these cells are haploid, meaning they have only one set of chromosomes, which is what we're going to need. But they're going to undergo another round of meiosis called meiosis two. And now we have four spermatids. So one primary sex cell becomes four spermatids, which will now undergo the process of spermiogenesis, where they go from looking just like any other cell to becoming a sperm cell. And we'll talk about the structure of them in just a moment. This process from spermatogonia all the way down to a functional sperm takes about 64 days. As I mentioned before, this is a continuous process. It's happening every day. The average man is producing 100 to 300 million of these a day, give or take. So this is a constant process. And now when we compare this later to the process of producing an egg, in the end, one primary sex cell is only going to make one egg. And then the leftover cells are going to be called polar bodies, because we need millions and millions of sperm. We only need one oocyte or one egg. So what happens during spermiogenesis to turn the spermatid into a sperm? You're going to see a loss of cytoplasm. There's very little cytoplasm in a sperm cell. I'll show you what a spermatizoma looks like in just a moment. And then it's going to develop the other pieces that it needs. Now, once we have these immature sperm produced, they're going to leave the seminiferous tubules where they travel to the epididymis. And that's where the further maturation of sperm occurs. So sperm are produced in the seminiferous tubules. They mature in the epididymis. All right, so here we see what a sperm looks like. Sperm are one of the tiniest cells that a human has. The volume of a single spermatizoma is 85,000 times less than that of an egg. So an egg has a massive amount, an oocyte has a massive amount of cytoplasm. A sperm has barely none, which is why when fertilization occurs, the egg has all the food that's going to keep this soon to be cluster of cells alive until the femur reproductive tract kicks in. All right, so I've already mentioned hundreds of millions of spermatizoma are produced each day, whereas a female is only going to produce that one oocyte. We've covered that in several videos now. So let's look at the structure of a sperm and see how it plays a big role in its function. So we have a head, a midpiece, and a tail. So the head of the sperm is gonna have this really compact nucleus. It's gonna have that one set of chromosomes that it's going to 23 chromosomes, that it's going to devote to fertilizing the egg, producing a diploid human being. It also has a cap here called the acrizome. The acrizome is full of lysosomal or digestive enzymes. It plays a role in wearing away the outside of the egg so that a sperm can actually enter and fertilize the egg. And we'll cover fertilization in a different unit. We'll cover with pregnancy. So this acrizome cap is very important for making it so a sperm can reach and fertilize an egg. But this cap does, you'll see as sperm are going to mature, this cap will be removed and then the sperm will be able to transplant that nucleus. So the head has this nucleus, this one set of chromosomes, which is a tiny bit of cytoplasm. The midpiece is full of mitochondria. Mitochondria produce energy. What do you think the energy is going to be needed for? To make that tail move. So the ATP reduction is critical to keeping the flagella moving so sperm can move and reach their destination. You'll also see the midpiece has a centriole in it. That single centrioles will produce the entire flagellum. Very, very cool. So that's the, excuse me, the midpiece. The tail is going to be that one single flagellum. The flagella in a human sperm is going to function like a whip. If you take microbiology with me, you know that the flagella on bacteria are much more complex. They have a rotary motor type function. So we talked about that acrosone cap, very, very important. We talked about what's in the nucleus. One more just important thing to me to note is so we have the mitochondria in the midpiece that make ATP, but the tail is what needs ATP. So how do we get ATP from where it's produced to where it's needed? Now ATP can diffuse, but it diffuses really, really slowly. This is one of the cells in your body that relies the most on creatine phosphate. So when we learned about metabolism and energy production, remember that your body only has two or three seconds worth of ATP stored at any moment, but creatine phosphate is an energy and phosphate donor that can turn ADP back into ATP, which might buy your body 10 to 15 seconds of ATP if you didn't have a metabolism. So creatine phosphate can come along and when it sees an ADP that's been spent, it can say here, take my extra energy, take my third phosphate, become ATP and get back to work. Now the reason this is so important is because in this area especially, we'd have three to four times as much creatine phosphate in this area than we would have ATP. And that means that it's much easier to recycle creatine phosphate and then let it recycle ATP than to have ATP travel all the way back, or ADP sorry, travel all the way back to the mitochondria, become ATP again and go back to the tail. And that's because especially, this is the most important point here, creatine is way better at diffusing than ADP and ATP is. Creatine phosphate can diffuse 2,000 times faster than ADP and creatine phosphate or the phospho creatine, the source of creatine phosphate can diffuse, it diffuses seven times faster than ATP does. I think I said so, creatine phosphate diffuses 2,000 times faster than ADP sorry and seven times faster than ATP. So those numbers don't matter so much but what that means is it's way easier for creatine phosphate to go to the tail, find an ADP, recycle it, regenerate it. So now it's an ATP again and then go back to the mitochondria and pick up more energy. So creatine phosphate forms this shuttle that allows sperm to have all the energy they need. Now if you will cover this in another video but if you're wondering where they get the fuel, it's primarily fructose. So your seminal vesicles which produce about 60% of semen, very rich in fructose. So your sperm like to use fructose for fuel there. Okay, so that's gonna be sperm production and the structure and function of A spermatozoa. I hope this helps, have a wonderful day, be blessed.