Male Reproductive System: Other

by Geoffrey Meyer, PhD

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    00:01 In this lecture, I’m going to describe the accessory ducts and also the glands associated with the male reproductive system. It’s important at the end of this lecture that you are able to identify each of the duct systems and know what role they have in transporting sperm from the testes to the penis. I want you to understand and identify the different sorts of accessory glands, the prostate, seminal vesicle, and also their role in nourishing and protecting the sperm after ejaculation. You should all have a good understanding also of the structure of the penis and how blood flow going to the penis creates an erection.

    01:01 These ducts are very important because they store the mature spermatozoa. The glands add secretions to the ejaculate to provide the nourishment for those spermatozoa in the ejaculate.

    01:16 And it’s important to understand the structure of the penis as an organ of copulation in the male, and also, the organ that delivers urine outside the body. It contains the urethra.

    01:32 And the urethra is a common conduit for delivering not only urine but also the ejaculate.

    01:42 This slide illustrates the major organs of the male reproductive system. And I’ve listed those organs on the left-hand side of the slide. I’ve already described the testis in a separate lecture. In this lecture, I’m going to concentrate on the other structures listed.

    02:06 Just look at the diagram and locate the testis. It’s a green circular structure suspended in the scrotum towards the base of the section of the slide. The bluey stained or colored component wrapping itself around, that posterior aspect of the testis is the epididymis, the ductus epididymis. And then that’s continuous with a long tube you see running up around the back of the bladder, that’s the vas or ductus deferens. And that joins both the seminal vesicle and the prostate gland which are the two major accessory glands I’m going to describe. And then, the delivery of both urine and also spermatozoa from the vas deferens is delivered into the urethra. You can see the urethra initially coming from the bladder.

    03:13 The urethra passes down through the prostate, and then through a membranous component between the prostate before it enters the penis. So the urethra has both a prostatic component, a membranous component, and also a penile component. You can also see the ejaculatory ducts coming from the seminal vesicle, passing into the prostate gland. It’s important to understand the relationships of all these organs that I’ve just described, so that when we go through these organs in more detail, you’re aware of their relationship and the interaction each has with each other. In this slide, you can see an illustration of the duct system that takes the spermatozoa away from the testis. And I’ve listed each of these ducts on the right-hand side and numbered them because I’m going to refer to these numbers to describe the duct system. Firstly, look at the testis. I’ve already described the testis in another lecture. But the testis has a capsule around it called the tunica albuginea. And that capsule divides the testis into a number of lobules. And these testicular lobules contain one to four long coiled tubes we call seminiferous tubule. And each of these tubules can be up to 50 centimeters long. So this is its enormous length of epithelium that is part of spermatogenic epithelium. This tube was aligned by seminiferous epithelium, which is the epithelium giving rise to the spermatogenic cells or containing the spermatogenic cells. And the final product of this epithelium is to release spermatozoa into the lumen of these tubules which then move their way towards the mediastinum of the testis. Before they get into the mediastinum of the testis, they pass into straight tubules. You can see them illustrated in the diagram and labelled 1 here. Those straight tubules then carry the spermatozoa along with fluid, into the mediastinum of the testis, into channels referred to as the rete testis, shown here labelled 2. And then, the fluid and the spermatozoa travel from the mediastinum into the epididymis via the efferent ducts. These efferent ducts are about 12 to 20 of them, they link the testis to the epididymis, the ductus epididymis. When you look at the epididymis, which is labelled 4 here, it’s a very long coiled tube. It can range from four to about six meters in length. It’s the site where sperm are going to go through their final maturation phase and become motile. It’s also the site that they’re stored.

    06:53 Now, that epididymis has a head, a body, and a tail. The head is the component, the coil part of the epididymis right up next to the testis, joining the testis via these efferent ducts. The body is in the bulk of the epididymis passing around the posterior aspect of the testis. And then it starts to one coil at the tail region and it’s continuous then with the vas deferens labelled here, 5. I want you to keep in your minds a memory of this particular picture, because I’m going to refer now to all the different parts of the epididymis, the vas deferens and even all the duct systems coming out of the testis.

    07:46 And I’m going to describe their histological features or characteristics and their importance.

    07:55 Now on the right-hand side, you can see a histological section. This is taken right near where the seminiferous tubules become continuous with the straight tubule, number 1 in the diagram. You can see the seminiferous tubule, the seminiferous epithelium is minimal.

    08:17 It’s not as thick as you see in other parts of the testis. It doesn’t contain a vast number of spermatogenic cells because the epithelium is changing as it moves from the seminiferous tubule to the straight tubule. In the straight tubule, it’s becoming cuboidal or even columnar, there're a variety of shapes of the epithelial cells, but generally speaking, they adopt the cuboidal type of appearance. And then the epithelium is maintained as we pass through the rete testis shown here on the right-hand section, and it’s equivalent to this section area on the diagram number 2. These are just huge channels or spaces that collect all the fluid containing the spermatozoa from the seminiferous tubules.

    09:16 And they have a cuboidal, sometimes an even squamous epithelium. There is a little bit of a variety in these tubes. It’s particularly not that important, nor are the straight tubules in terms of defining their histology and their epithelial characteristics. The important point is that they are channels that are going to carry the spermatozoa from the testis up towards the epididymis. And then the efferent tubules look rather strange. They’re labelled 3 on the diagram, and they’re shown here in the histological section. Have a look at the epithelium. It’s rather an uneven surface, an undulating or corrugated type lumen due to the difference in the types of epithelial cells here. Some are cuboidal, some are columnar.

    10:17 It looks as though some are even pseudostratified. It doesn’t matter too much. We tend to just term this particular tube a pseudostratified epithelium because really when you look at a number of sections through these tubes, the bulk of the epithelia illustrates a pseudostratified appearance. They have, on their surface, cilia. You can see some ciliated cells in this image.

    10:49 And those cilia help to move the fluid along and carry therefore the spermatozoa into the epididymis. In the center of the lumen, you can see some red stained components that represent spermatozoa being transported along these ducts, the efferent ducts. Now, we’re up towards the epididymis. On the right-hand side, you can see a section taken through the testis and the epididymis. Testis is shown here on the label, and then the epididymis is shown on the far right label. In between are the efferent ducts. Have a look at this histological section, including the testis, the efferent ducts, and the ductus epididymis.

    11:46 And now, have a look at the figure. And just in your own mind, draw a line where you think the section passed when the histologist sliced the section through the testis, the efferent duct, and the epididymis to obtain the section that you’re looking at here. It is important sometimes in histology to be able to work out the orientation of how sections were actually taken through an organ. That’s just a little exercise for you to do partly of interest. Well, we now are looking at the epididymis. Have a look at the two sections shown here. Even though they are taken at two different magnifications, there are a few features I wish to point at. First of all, the bulk of the cells are called principal cells.

    12:46 They exhibit stereocilia, long extended branching microvillus-like processes from the apex of their cells. They’re important to be able to absorb an enormous amount of fluid from the contents, from the lumen of the epididymis. Because the epididymis, one function is to absorb all the fluid that moves from the testis up into the epididymis duct, the fluid that’s added by secretions from the seminiferous tubule and by a secretion from the cells in the ducts I’ve already dealt with leading to the epididymis.

    13:32 These stereocilia are then very important for that absorptive role. In the center of the lumen of each section through the epididymis shown here, you can see spermatozoa, many, many, many spermatozoa. The testis produces 300 million spermatozoa per day. Very different to the ovary, whereby, only one oocyte is ovulated every month. Huge contrast.

    14:12 When you look at the epididymis, you can see smooth muscle around the wall, just underneath the lamina propria supporting the epithelium. On the left-hand side, you don’t see a lot of smooth muscles. On the right-hand side where the smooth muscle is labeled, you do.

    14:32 And that’s because, on the left-hand section, you’re looking at a section through the epididymis taken towards the head of the epididymis, where really the prime role of the epididymis here is absorption. And therefore, you see a lot of stereocilia, as I’ve pointed out, on the apex of many other principal cells. Whereas, the section on the right contains a lot of smooth muscles. And that smooth muscle is important because, during ejaculation, that muscle is going to contract and force those spermatozoa along into the vas deferens which also contracts to expel the spermatozoa out through the penis during ejaculation.

    15:22 So that muscle is very important and there are lots of layers of muscle there. The other thing you can’t notice really on this section, but I’ll tell you about it anyway, is that on the left-hand side, the epithelial cells that are doing all the absorption, they are very busy cells. They are tall. They are about 30 to 40 microns in height. Whereas, the ones on the right-hand side where the prime role is merely to move the spermatozoa into the vas deferens during ejaculation, these epithelial cells are half that size, half that height, and they don’t exhibit as many stereocilia on their surfaces. The vas deferens again is very different. The ductus deferens or vas deferens is a muscular tube. It has a lot of smooth muscles wrapped around it. And the layers of smooth muscle are orientated in different directions, again, to ensure very rapid force of all expulsion of the spermatozoa in the lumen during ejaculation. The epithelium also contains stereocilia, and sometimes the epithelial forms this longitudinal fold, which often might seem quite a characteristic structure when you compare them with other ducts, and not only in the male reproductive system, but in other tubes of the body. Probably the most distinguishing characteristic here though is the very, very thick smooth muscle layers around the wall. Here is a section through the spermatic cord. The spermatic cord at least contains a number of components.

    17:22 On the left-hand side of this section, the tube or the very small lumen and the thick muscular wall is the vas deferens or ductus deferens. Other structures you see here that dominate are blood vessels, more towards the right-hand edge of the section. Those blood vessels consist of components or branches of the testicular artery, and also, veins of the pampiniform plexus. When I spoke about the testis in another lecture, I explained that the testis has to be maintained outside the body cavity. Spermatogenesis only occurs if the temperature of the testis is about two to three degrees below normal body temperature. And that’s achieved because the blood vessel supplying the testis, the testicular artery, coils as it moves down towards the testis, and it has a very intimate relationship to the veins that drain the testis, the pampiniform plexus of veins. And those veins carry cooler blood back to the body, back to the heart.

    18:46 And the relationship between the testicular artery, being very coiled, and this pampiniform plexus enables the blood to become to be cooled by these veins as it passes down towards the testis. That’s the primary role of this pampiniform plexus. It’s the primary structural specialization that cools the testis by cooling the blood leading to the testis. You can’t see it clearly on this slide, but if you look very carefully around the vas deferens, the rather red stained regions represent section through the cremaster muscle. The cremaster muscle lifts the testis or lowers the testis in the scrotum. Scrotum also has a duct muscle through it and that contracts or relaxes. And this process of contracting or relaxing creates the scrotum as being rather a tight sac holding the testis or rather a loose flaccid sac, and that’s designed to conserve heat loss or create heat again in a cold temperature, for instance, or heat retention in cold temperatures that scrotum will contract and wrinkle to maintain or at least reduce heat loss. So you have this variety of mechanisms designed to make sure the testis operates at a temperature below body temperature. The accessory glands consist mainly of the prostate gland and the seminal vesicle, and they are the two glands that I’m going to describe now. Let’s go back to this diagram just to remind you of where the seminal vesicle lies and where the prostate lies. The seminal vesicle, you can see in this diagram, lies just at the posterior aspect of the bladder, at least from the angle you’re looking at. And the prostate gland is below the bladder. And just refresh your memories about the ejaculatory duct coming from the seminal vesicle into the prostate to join the prostatic urethra. And there, the secretion products from the seminal vesicle and the prostate will pass into the urethra during ejaculation and flash the spermatozoa out that have been delivered to the urethra by contraction of the vas deferens and also the epididymis. Let’s now have a look at this seminal vesicle in a bit more detail. Here, you can see a number of different features that are characteristic of the seminal vesicle. It has got a fairly thick muscular wall. And it has got a very, very folded mucosa.

    22:04 You’ll see that more clearly on the right-hand side section taken at high magnification.

    22:11 This seminal vesicle forms a very long convoluted sac, and it all connects to the ejaculatory duct. And this sac, as I mentioned, is convoluted. It’s very, very folded with lots of muscle making up the wall. The epithelium secretes fluid, and that fluid is rich in fructose which is the major energy supply for the sperm. Often, you see the seminal vesicle containing lots of colloid type material in the lumen. This reflects the fluid containing all these fructose. The prostate gland is the largest accessory gland. It secretes a watery slightly alkaline fluid. It also secretes fibrinolysin which liquefies the semen. Whereas, the seminal vesicle secretes a yellowish, whitish solution that’s rich in fructose. When you look at the structure of the prostate gland, there are separate units illustrated on the diagram.

    23:34 Look closely at the urethra, and also, at the ejaculatory duct coming into the prostatic tissues. Around that area, immediately around the urethra, is an area or a zone, if you like, consisting of what’s labelled there as mucosal glands. Then there is a middle submucosal gland layer, and then an outer peripheral or the main prostatic gland layer.

    24:08 These three separate zones are quite significant as I’ll explain to you in a moment.

    24:15 The glandular tissue, even though they are restricted within these three zones, three separate zones, and the products are delivered via the ducts into the urethra, the glandular tissue, if you look at all through these zones, is very similar. The epithelium is generally described as being columnar, but there is variation in the sort of arrangement of the epithelium that you often see at various parts of the prostatic gland. And these epithelial surfaces can often become nodular, and that creates a problem. If it occurs in the glandular tissue immediately around the urethra, then it can impinge on the lumen of the urethra, and therefore, make urination a long slow process. This increases as the males age.

    25:12 There is another characteristic also of the prostate, and that is the presence of prostatic concretions called corpora amylaceas. These build up again with age. They become calcified.

    25:29 And again, if they build up in a zone immediately around the urethra, then they can impinge on the urethra, and therefore again, make urination a long slow process. Now, these cells also can become cancerous. Prostate cancer is the most common cancer in males.

    25:56 And it tends to occur in the outer peripheral main prostatic glands. And there, the cancers can develop and take over a lot of the mass of that outer peripheral zone. And that can be digitally palpated through a rectal examination. But the problem is that when these cancers grow within the prostate and maybe even start to impinge on the urethra, and the male experiences a long slow urination process, then it’s too late because by that stage, the prostate cancer has metastasized. It’s spread to other parts of the body. The prostate gland secretes many components of the seminal fluid. One is prostate-specific antigen. It’s secreted into the seminal fluid or into the secretions of the prostate, but a bit of it also leaks across into the blood stream. So it can be detected in blood. And in normal individuals, the levels are lessened about four nanograms per mil. But in prostate cancers, the secretion of this prostate-specific antigen can increase. So, a blood test can reveal higher concentrations of this prostate-specific antigen or PSA in the blood. And that is an indication that there are these cancerous cells present in the prostate. So, males are encouraged over a certain age to have a regular blood test to detect the levels of this PSA.

    27:54 Same as females, have a regular Pap smear to detect the presence of cancer cells that may be exfoliated from the cervix into the vagina. And similarly, breasts can be scanned. The mammary gland can be scanned for the presence of cancer cells in the breast, because both the change in the hormonal environment throughout the female menstrual cycle and genetic predisposition are risk factors for breast cancer. So there are these different methods of scanning both female and male reproductive organs to try and detect these cancerous events. The penis is the erectile organ of the male. It’s a copulatory organ. And if you section through the penis, you can see the erectile tissue. The main erectile cylinders or tissues are called the corpora cavernosa. They are really just large spaces that engorge with blood, and those large spaces are lined by endothelium, the normal line you’d expect in blood vessels.

    29:20 The urethra is within another tubular structure called the corpus spongiosum. That doesn’t become erectile tissue. It maintains the patency of the urethra. So during ejaculation, erection is maintained but also towards the lumen of the urethra maintained open. If we now look at the erectile process, in this diagram, you see pictures or diagrams of the penis, the flaccid penis, when it’s usually acting as part of the urinary system, and then the erect penis when it’s acting as part of the reproductive system. And on the right-hand side, you see a section through the penis, all be it rather faint, just to point out the corpora cavernosas, the erectile components of the penis that become engorged with blood. And on the right-hand section through the penis, you can see a very faint outline of the male urethra enclosed by the corpus spongiosum. Normally in the flaccid penis, when blood comes down, it flows a little bit into the corpora cavernosums but it’s diverted mostly into the venous system and returned back towards the heart. Sphincters close down so that blood tends to be diverted from the corpus carvenosums or at least a lot of blood. Under sexual stimulation, though, that sphincter can then open up. So more blood is diverted into the corpora cavernosums, and so the penis becomes erect, that area becomes engorged with blood. And it becomes engorged with blood because of the relaxation of muscles, smooth muscle cells around the vessels and the opening of that supply to the corpora cavernosums. But at the same time, the venous return out of the penis is restricted, because the vein coming out of the penis through the penile areas comes out at an oblique angle. And so when the penis becomes erect, that vein is closed off, and therefore, blood is not then continually flowing through the penis, hence, the erection. Here again is the corpus cavernosums that is the erectile tissue, and the corpus spongiosum is the area around the urethra. Well, let’s now summarize what I’ve covered in this lecture. It’s important to understand that the epididymis is the location for sperm to become mature. Sperms tend to spend 10 to 12 days in the epididymis going through this process, and they gain motility. Then there's all duct system that leads the sperm to the epididymis coming from the testis. It’s important to understand those as well.

    32:46 And then there’s a seminal vesicle that secretes fructose, the main energy source for the sperm, understand its structure. It’s a tubular convoluted glandular tissue.

    33:00 And then make sure you recall the importance of the prostate gland, its secretory product, and also the way in which the glands are arranged, and therefore, the occurrence of conditions that can restrict the flow of urine, and also the conditions that can lead to cancerous lesions in the prostate. And finally, recall the structure of the penis, the erectile tissue, and the process in which that erectile tissue becomes engorged, and therefore, leads to erection of the penis, so it become into the copulatory organ. Well, thank you for listening to this lecture.

    33:41 I hope you now know something about the duct systems in the reproductive system of the male, and also knowledge about the very important accessory glands. And, of course, the structure and function of the penis. So thank you again for listening to this lecture.

    About the Lecture

    The lecture Male Reproductive System: Other by Geoffrey Meyer, PhD is from the course Reproductive Histology. It contains the following chapters:

    • Male Reproductive System: Other
    • Testis, epididymis and the vas deferens
    • Epididymis
    • Ductus deferens and spermatic cord
    • Accessory sex glands
    • Prostate gland
    • Penis

    Included Quiz Questions

    1. has a prostatic part, membranous part and a penile part
    2. joins the ductus (vas) deferens to the prostate gland and seminal vesicle
    3. extend from the kidney to the bladder
    4. has a prostatic part and a penile part only
    5. has a penile part only
    1. Rete testis
    2. Straight tubules
    3. Ductuli efferentes (efferent ducts)
    4. Head of the epididymis
    5. Seminiferous tubules
    1. a number of layers of smooth muscle
    2. a uneven, epithelial surface
    3. very tall epithelial cells with microvilli
    4. very tall epithelial cells with stereocilia
    5. tall principal cells with cilia
    1. cooling of the arterial supply to the testis by the pampiniform plexus of veins draining the testis
    2. contraction of the cremaster muscle to minimise heat loss from the scrotum
    3. cooling of the pampiniform plexus arterial supply to the testis by the testicular vein draining the testis
    4. contraction of the dartos muscle when exposed to the cold, to raise the testis inside the scrotum close to the abdominal cavity, and so retain warmth
    5. the thickness of the tunica albuginea (capsule) of the testis that insulates the testis from a higher body temperature
    1. The prostate secretes a watery, alkaline fluid rich in fibrolysin which liquefies semen
    2. The prostate secretes a yellowish, whitish fluid rich in fructose which liquefies semen
    3. The seminal vesicle secretes a watery, alkaline fluid rich in fructose which liquefies semen
    4. The seminal vesicle can accumulate concretions that may impinge on the male urethra and prevent comfortable and rapid urination.
    5. The prostate secretes a watery, alkaline fluid rich in fructose which nourishes sperm
    1. is immediately surrounded by non - erectile tissue of the corpus spongiosum
    2. is immediately surrounded by erectile tissue of the corpus cavernosum
    3. is immediately surrounded by the tunica albuginea
    4. is immediately surrounded by erectile tissue of the corpus spongiosum
    5. is immediately surrounded by non-erectile tissue of the corpus cavernosum

    Author of lecture Male Reproductive System: Other

     Geoffrey Meyer, PhD

    Geoffrey Meyer, PhD

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