All right. Hello everyone. Welcome to your lecture on the male anatomy. So these are the learning outcomes for this lecture. You're going to need to know all this in preparation for any quizzes or exams that are coming up. So you must know and list the basic structures of the human reproductive system and summarize the functions of each. And more specifically for the male anatomy, you have to describe the structures of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing sperm. It's also important that you describe the composition of semen. All right, so this is a very broad overview. These are all terms that you are going to really have to know and I'll go through each of these in enough detail in the following slides. But um if we remember from last lecture, we know that the gametes for males are sperm and sperm are produced in the testes. And all of these other terms we'll get to know a little bit more, but this is a good slide to um start writing flashcards with or just know that you um must recognize these terms on an exam. It's also a good idea to start recognizing this image. Um this is a great image for me to test you on. Um, the way that I would like you to read this image is actually from the bottom up. Okay. So, we're going to start, if I can draw, we're going to start down here. So, this is where I'd like you to start. So, these are the testes and they're in something called the scrotum, which we'll get to. There's a structure called the epidmus that sits right on top of the testes. And then from the epidmus, you'll see that there is this long tube. Okay. Do you see that? You're going to start to follow that all the way down. You're passing all of these accessory glands. They're going to go all the way down the penis and it's going to eventually um evacuate the body through ejaculation. So, this is how I'd like you to to start recognizing this. Start from the bottom here and work your way around. This is another um really great picture that I'd like you to be familiar with. This shows a cross-section of the testes. So, we're really going to be looking at are these muscles. We're going to be looking at um these layers of skin. We're going to look at these folds and then these all of these convoluted tube channels that you see, these are going to be important. These are called the seminifpherous tubules, but we'll get into that. Okay, so talking about the testes and the scrotum, um you do not need to know exact measurements, but do know that the testes are relatively small and they they are um housed in a fleshy pouch called the scrotum. So the scrotum is divided into two chambers or scrotal cavities and each cavity holds one test. So there are two testes. So there are two scrotal cavities and there's a layer of smooth muscle around that scrotum that's called the dartose and that's in the scrotal dermis or the scrotal skin. And so the dartose muscle is responsible for wrinkling the scrotum to increase the surface area for warm air circulation around the testes. And it's also important to know that the dartose muscle is capable of prolonged contraction. Okay, so this is the first muscle of the scrotum. The second one that we need to know is the craymaster muscle which lies just below the scrotal dermis and contraction of the muscle just like any other muscle we think about the origin and insertion of it. Um contraction of the cray masteraster muscle pulls the testes closer to the body but the cray master in comparison to the dartose is used for more shorter contractile periods. Okay. So let's talk about the layers of the scrotum now. So since the testes and the scrotum lie below the pelvic cavity, they're not necessarily central to the body like we would think of maybe the chest cavity or the paritonyium. And so it's really important that um we have structures in place to help protect the testes, right? Cuz they're producing sperm. So each testes is wrapped in a fibrous capsule called the tunica albiggina. And um this is that fibrous capsule. You could see it here. It's surrounding these convoluted tubules. Like I said, those are the seminifpherous um tubules. And there also are two cirrus layers called the tunica vaginalis. Okay, so it's not really labeled here, but this blue area, these are the cirrus layers. Cirrus just means that they're like watery um or you know, they they're slippery, so they help reduce friction, which is important again because these testes lie below the pelvic cavity. So let's talk about the testes and temperature control. Once again, these muscles are super important for you to know. Okay, so it's a good slide to know, but the darttos muscle um is made up of involuntary smooth muscle responsible for longer control of the testes. Other parts of our body that are made up of involuntary smooth muscle include, for example, your colon or your intestines. you don't necessarily have control of of your colon. You know, you don't say, "Okay, now I'm going to contract my colon." So that's why it's called involuntary. And it's also why this is under parasympathetic control. The fight or I'm sorry, the parasympathetic control is the rest and digest phase, right? This is in in comparison to the craymaster muscle which is for voluntary um movement. So voluntary strided muscle which is responsible for elevation and descending of the testes in response to a more sudden temperature change. Okay. So because of this word sudden temperature change we can think of it as being under the control of the sympathetic nervous system. Right? So that fight orflight response. So it's important for you to be able to distinguish in what cases the dartose muscle might be activated which instances the craymaster muscle might be activated. But it's also important to know that these work together, right, to um either ascend or descend the testes. And it's important that um we control the temperature of the testes because normal sperm development requires temperatures that are about 2° Fahrenheit lower than the body temperature. So this is another reason why the testes are positioned outside the pelvic cavity, right? So they're not really central to the body. And um these muscles once again the dartose and craymaster help maintain the proper temperature. So let's go through some examples. So when the air or body temperature increases so say it's a really hot day the dartose and craymaster muscle will relax right. So um the smoothing of the skin of the scrotum and um the testes will move away from the body. They don't want to get too hot. they need to maintain this this steady temperature for um normal sperm development. So how about when the temperature decreases? So say you're doing a cold plunge, right? So this is an example where the dart and craymaster muscle will contract and um they'll contract and that'll cause the scrotum skin to wrinkle and will move the testes closer to the body so that they can again be temperature controlled for normal sperm development. Okay, so we've seen this picture before. Now we're really getting into it. So the collagen fibers from the tunica abugina extend into the testes which form these um things called septa, which is really just a bunch of tissue that separates the testes into about 250 lobules or lobes. And inside these loes, you'll find the seminifpherous tubules. These are tightly coiled tubes within each lob. And this is the site for sperm production. Sperm production, the fancy word for it is called spermatogenesis. And it's very important that you start to realize that there's going to be a lot of words that sound similar in this PowerPoint, but it's important now to just keep in mind that spermatogenesis equals sperm production. And sperm production happens in these structures of seminifpherous tubules. So taking a closer look into the seminifpherous tubules and what are the key players in them. So the cells located in the tubules we have germ cells first which are stem cells that produce sperm. We also have cerolei cells. This is a very specialized type of cell that nurtures and provides structural support for sperm cells during development. So this picture right here is important. It's a hisytologology slide. So this is a real tissue example. um you have the cerolei nuclei of these cells, right? So this is inside the seminifpherous tubule. This is a cross-section of it. That's why you see an empty space in the middle. And then let's talk about the cells located in the interstitial space or this area, right? So interstitial meaning outside or in between. So the interstitial spaces have these very specialized cells called latic cells. And latic cells produce the male sex hormones which are commonly referred to as androgens. The main one that we're concerned with is the hormone testosterone and latic cells are important for stimulating and controlling mitosis and meiosis. And we'll come to know that testosterone has a lot of different functions as well. So this is the interstitial space and these are the latic cells. This is just another um great picture. You see how these are cross-sections of the seminifpherous tubules. So this means that all this white space right here that's the interstitial space and this is a cartoon depiction of that as well interstitial space and the cells associated with that and then these are the sati cells which sometimes are also called nurse cells because they do nurture the development of sperm. So spermatogenesis or sperm production begins at puberty in males and continues until late in life sometimes even after the age of 70. Right. So this is a large chunk of time that males are undergoing spermatogenesis. And this process requires a series of cell divisions in the seminifpherous tubules. Each division produces a daughter cell that is pushed towards the lumen. Lumen meaning opening of the tubule. Okay. So it's kind of a ground up approach. We'll see that as we go up, we go towards the lumen of the seminifpherous tubules. We'll see that the sperm are more mature. And spermatogenesis, if we were to simplify it, has three main processes. The mitosis of stem cells, meiosis, and then a word called spermioenesis. Okay, notice the difference. Spermioenesis versus spermatogenesis. So, it's really important that you have these two terms clear in your mind. This entire process of sperm production takes about 2 months. We said in previous lectures that about half a billion uh sperm cells are produced each day. So this means that this entire process takes 2 months but there is some temporal delay right so not at all times um all the sperm will be immature there's going to be different phases in which they mature this is another kind of um simplified chart to help you recognize the steps of spatogenesis you see that star so you know it's important but the first step is mitoic proliferation proliferation just means to increase the cell number right so it's producing in lots of spermatogonia. Spermatagonia being immature sperm. Now, one daughter cell always stays behind while others get pushed towards the lumen to continue on in the process. And why do you think that is? So, it's important that one daughter cell that is diploid, right? Cuz we're talking about mitosis. It's important that one daughter cell stays so that this process can continue over and over again. Mitosis doesn't just happen out of thin air. You need that hloid or sorry that diploid cell this daughter cell to be there so that this process can continue. The second step of smatogenesis will be meiosis the two rounds of it right meiosis one and two and it generates genetic diversity. So this is the main point I want you to know about meiosis and this process has a chromosome number in the product is four hloids formatids. this case from attitudes being hoid. The last step is spermioenesis which is cell remodeling of those sperm to finally be what we think of as sperm. So these guys right here. Okay. So this process involves the packaging of the chromosomes for effective delivery to the oite upon fertilization. This is another great diagram that you can refer to for this process. Um and it's quite simple u simple. So we have one two and then the third step. So what's really interesting um I've always found interesting at least about this process of spermatogenesis is that it involves both mitosis and meiosis. And because of this we actually need a separation between these two processes or else the body might um respond in a negative way and mount an immune response against us. So we need separation for these processes due to the fact that during meiosis we have the production of genetically unique cells. Okay. So now we have this product of hloid cells that are recognized by the immune system as foreign cells or not self cells. The immune system is great at detecting this. It detects the viruses and any other cell in our body that does not look like our cell. And so um we need to make sure that there is a compartment a separation between mitosis and meiosis so that these hloid cells are not destroyed by the immune system. It's also important that we have these compartments to create a testosterone rich micro environment. Testosterone will have a lot of different functions, but the most important thing is for cell proliferation and overall just helps the process move along. You need testosterone for these sperm to move along in the process of spermatogenesis and um later on spermioenesis. So these are the compartments that I was talking about. You have the aduminal meaning near the lumen. Get my screen again. Near the lumen. Okay. Okay. So this is ad ruminal space and then you have the basil compartment. Basil meaning base right. So this is the base of the cell base of the um of the seminate first tubules actually. And separating these two compartments are tight junctions created by cerolei cells. So this blood barrier right here they're actually cerolely cells and they create almost like a gate. So they only allow certain ions and nutrients to pass which is super important so that immune cells don't permeate into the ad luminal space right because this is meiosis and this is mitosis. Okay. So let's talk about the third step a little bit more of spermatogenesis which is spermioenesis and cell remodeling. So this is a period of physical maturation for the spermatids. Um and this is a time where they develop into more mature sperm. So the sperm will enter the fluid in the lumen of the seminifpherous tubules. So the opening right lumen meaning opening. It's also really important that spermioenesis compacts the nuclear material into the head of the sperm for easier delivery upon fertilization. So let's talk a little bit about the anatomy of the sperm now. So we have um four distinct regions. The head, the middle piece, and the tail. There's also in between here the neck. Neck. But you don't really need to know that. It's just like our neck. It connects the head to the middle piece. Okay. So I'm going change this to three distinct regions. So you have the head which contains the nucleus and the chromosomes. It also contains an acrosome tip. Acrosome just means that there's enzymes associated with it to help penetrate the oasite. Next, we have the middle piece. Really important here is that there's lots and lots of mitochondria. Okay, this is the one time where I will accept that mitochondria really is the powerhouse of this sperm. Mitochondria need that um to produce that ATP, that energy for movement, right? Because these sperm have a super long journey ahead of them. Last is the tail which moves the sperm for propulsion or quote swimming. This is another figure. We have the head with the acrosome tip with all those really important enzymes. This is the uh the neck, the middle piece with the mitochondria and then the tail. So since spermioenesis has a lot of different steps, lots of different things can happen and sometimes we don't always end up with this normal sperm with the with the three distinct regions that we talked about. Sometimes there might be head defects. Sometimes there's even two heads. If there's no acrome then um that sperm cannot permeate the oite and that's really bad because fertilization cannot take place in that um capacity. There also might be midpiece defects which is important because um there might be some mitochondrial defects which means that the sperm doesn't have enough energy to make the long journey. Really commonly we also see some tail defects. They can either be too short or kind of kinkedked or maybe even too long. Some of them even have two tails. So we've talked about sperm. So let's not talk about semen. Right? So semen is not just sperm. Semen is sperm plus some other secretions from the accessory glands in the reproductive tract. So you might be thinking why is there a picture of 7 up on my screen? Well, we're going to get into it, but 7Up ends up being a really great pneummonic to help you remember remember the sperm ejaculation pathway. Okay, so seminiferous tubules, we already talked about that site of sperm production. Then we're going to go into the epidmus, the vast deference, the ejaculatory ducts. Unfortunately, N we didn't we couldn't think of anything. So the N in sevenup just means nothing. And then the semen will go through the urethra and outside the penis or the penile urethra. This again is that picture that I want you to really remember. you should be able to at some point before the exam you should be able to recognize all of these structures and be able to label them. Um, so this is the pathway, right? So we're starting off here, the epidmus go all the way here and out. This is a great pneummonic. So let's talk about the epidmus first. The E and seven up the first E. So the epidmus is a coil tube attached to the posterior the back portion of the testes and fluid currents from psyia remember those hairike structures they sweep up sperm into the epidmus. The main functions of the epidmus are to recycle damaged sperm. So those abnormal sperm that we saw. It's also a great site for storing and protecting mature sperm because it takes about 2 weeks for sperm to travel through the epdmus and complete their maturation. It's important to recognize that at this point the sperm moving into the vast deference which is the next structure might be physically mature but they're not mobile. They're immobile right? So the spermioenesis process is still taking place. They still need some maturation on that tail part. The next structure that we pass in semen ejaculation is the vast deference. You can also see it referred to online as the ductus deference. But if we call it the vast deference that it matches our pneummonic of seven up very nicely and the vast deference passes laterally to the urinary bladder and it curves down past the urer as you learned about that recently towards the prostate gland and I'll show you a picture of that in just a second. The walls are lined with smooth muscle which moves sperm via paristoic waves. Paristoic just means kind of like ocean waves. And one of the main structures of the vast deference is something called the ampula. So it's an enlarged part of the vast deference almost like this um where sperm can be stored for weeks again and this is a pit stop for sperm to combine with other gland secretions. So you see in the next picture that the ampula has many different gland secretions coming in to help create that that semen. So this is what I'm talking about right. So um you have the ductus deference which come from either testes right either epidmus. So there's two of them. So they're bilateral structures. This is the ampula or that enlarged region. And you see how it's kind of a pit stop, right? It's almost like a uh two roads connecting finally. And you'll see that all these glands, the seinal gland, the prostate gland, and the bul urethal glands, they're all going to help um create that semen. All right, the next 7 up is the ejaculatory duct, which is quite a short passageway. Again, no need to to recognize those um exact numbers, but it's formed by the joining of the ampula of the ductus or the vast [Music] deference with the duct of the seinal gland, one of those accessory glands. And this goes through the wall of the prostate and it empties into the urethra. So the male urethra is quite long. It's about 7 to 8 in long and it extends from the urinary bladder to the very tip of the penis. So the urethra is a passageway for both urinary and the reproductive systems. Okay. So we can have both urine and semen coming from this urethra. But there are some physiological mechanisms and also some um structural mechanisms in place to help ensure that urine and semen are not released at the same time. All right, so I've kind of already alluded to this, but these are the accessory glands that you're going to need to know. Okay, so we have the seminal glands, the prostate gland, and the bulb urethral glands. So these glands are important in producing the fluid component of semen. Okay, because semen is more than just sperm. Some other functions include activating the sperm and providing nutrients for motility. So, helping out with that tail and its function. They also generate parastolic contractions to propel sperm and semen to help keep the process going. And they also produce buffers to counteract the acidic environment of the urethra and the acidic environment that can be found in a in a vaginal canal. So, this is important because if an environment is too acidic, the sperm won't be able to survive the long journey. They have a long journey up the vaginal canal to find that O site and hopefully fertilize it. So the seminal glands um I would say these are really really important accessory glands. They're paired. There's one on each side. Um you might also see them called the seinal vesicles and they're important because they contribute the majority of the volume of semen. Okay. And their secretions contain fructose for metabolism which is important because this uh sperm need as much energy right to to help propel them and help them um find the oite. They also um these glands also secrete prostaglandins that stimulate smooth muscle along the male and female reproductive tracts. This helps with contraction um which helps keep the semen in the vaginal canal longer. There's also something called fibbrinogen that is secreted from the seminal glands which creates a temporary semen clot in the vagina which again is important to just make sure that the semen has um as much opportunity to stay in the vaginal canal so that fertilization might take place. And the secretions also can help stimulate sperm capacitation. Capacitation just meaning that they're finally mature and can um can function on their own. So the sperm begin beating the fugella or the tail and they become mobile. So these are the paracininal glands number four. This is the bladder number one. Okay. So you can see that they all meet up here and produce the majority of that semen volume. The next gland is a prostate gland which is a small round muscular organ. So it's number five here. and it surrounds the urethra as it leaves the urinary bladder like we saw. So prostatic fluid makes up about 20 to 30% of the volume of semen. Um it also contains something called cement plasmine which is a protein with some antibiotic properties and um antibiotic properties do tend to prevent UTI or urinary tract infections um in males. There's also some parastoaltic contractions of the prostate wall to help propel the secretions into the urethra to help things move along. And um if you think that you've heard of of prostate or prostate cancer, you're probably correct because unfortunately one in eight men in the US will be diagnosed with prostate cancer in their lifetime. So it is important um just to know where the prostate is and to know about prostate health. The last accessory glands that I'll talk about are the bulbal urethral glands. These are also paired. So there's two of them. That's why you see plural glands. They're located more at the base of the penis and they contribute less than 5% of semen. Okay? So, not much at all. But the secretions that they do have are thick and basic, so more alkaline as opposed to um acidic. And these secretions help lubricate the glands penis or the very tip of the penis. And these secretions can sometimes be referred to as pre-seinal fluid. Okay? So, it's not much, only 5% of that volume. So moving on to um the penis which is a tubular organ containing distal portions of the urethra and it introduces semen to the vagina during intercourse. It also conducts urine into the exterior through the urethra. Right? We know that it's in char this um organ is in charge for both reproductive and urinary health. And the three main regions that you'll need to know is the root which is fixed to the body wall, the body which is that tubular portion that extends out with erectile tissue which we'll get into. And then the gland's penis which is um very at the very end the distal end and it surrounds the external urethral orifice which is a very fancy way to just say the opening of the penis or the penile urethra. In some cases there um there also might be a prepuse or a foreskin if that was not circumcised um shortly after birth which is a fold of skin over the glands. So let's talk about some of the um the importance of the erection of the penis for sexual intercourse. So the body of the penis is made up of erectile tissue that is engorged or filled with blood during arousal. And this is because um the shaft or sorry yeah the body or shaft same thing the body is um made up of erectile tissue and lots of vascular channels lots of blood flow happening here. The two main structures that you'll need to know are the corporal cavernosa and the corpus spongiosum and I'll show you pictures of that. So the corpora cavinosis surround both sides of the penis versus the corp spongiosum is just one structure that surrounds the middle or the urethra. Individuals who may struggle with ED, also known as erectile dysfunction, may have difficulty getting or staying erect. And this is why medications that increase the blood flow, which are also called vasoddilators, right? They're often prescribed for this, such as Viagra, to help increase the blood flow to these erectile tissues, the corpus carnosa and the corpus. in a resting state. There isn't um much blood flow to the penis other than what is necessary to um help maintain it normally and help um uh send any nutrients that it needs. And the arterial branches, the blood vessels are constricted, right? We don't need a lot of blood flow. But during the erection, these um vessels, they dilate and these channels, they actually fill with blood to help um the penis get erect and stay erect. And this erection is under parasympathetic control. Now when we think about arousal and erection, we might want to think about more sympathetic control, right? This fight or flight, this um this energy adrenaline that's pumping through our body, but it's actually under parasympathetic control because if we think about blood flow, we want as much blood flowing to the corpus carnosa and the corpus spongiosum. And so we need this kind of resting state, this kind of rest and digest to help those vessels dilate and get as much blood flow to the penis as possible. Okay, so this is um a series of pictures just showing that this is a cross-section of the capora cabinosa and um the corpus spongiosum. You can see that the capora cabinosa on both sides versus a corpus