Ch. 18: Male Reproductive System

Ch 21: Male Reproductive System

Overview:

The goal of this lab is to examine the histology of the principal parts of the male reproductive tract.  Use Junquiera's or Wheater's texts and the diagram (below) as guides.  Understand the functional correlates of the architecture you observe, and be able to distinguish each of the components.  Pay attention to the disposition of the epithelium, note the special modifications of tubules and glands, and observe the amount and layering of connective tissue and smooth muscle.

Slide Descriptions

Webslide 0087_M:  Testis, human, 19 yr. M, Masson  [DigitalScope]

Note the following on this thick section:

1. Connective tissue tunica albuginea that constitutes a capsule from which septa extend, dividing the testis into lobules.


2. Seminiferous tubules, highly convoluted, surrounded by thin CT sheath. Find a good cross-section of a tubule, and with low power, note the organization of the germinal epithelium. The various cells types can be seen more clearly on Webslide #31.


3. In the loose connective tissue between the tubules are occasional groups of more intensely staining interstitial cells.  These are the Leydig cells which secrete testosterone. 

Webslide 0275_M (courtesy of U. of Mich.): Testis, human, H&E  [DigitalScope]

This section features part of the testis on the lower portion of the slide. Note the seminiferous tubules and Leydig cells. Present on the right hand side of the tunica albuginea is the mediastinum, a thickened portion of the tunica albuginea that contains the rete testis. The rete testis, the area where tubules coalesce and connect to efferent ductules, is shown as irregularly-shaped lumens lined by a simple cuboidal epithelium. Beyond the rete testis are efferent ductules with pseudostratified epithelium and prominent tufts of cilia. The upper right hand portion of the slide contains both efferent ductules and epididymis.

Webslide 0031_M:  Testis, hamster, 1.5 µm, AF-TB  [DigitalScope]

Observe the following in this well-preserved thin section:

1. CT around seminiferous tubule.


2. Leydig cells and numerous capillaries in interstitium.


3. Stages in spermatogenesis, progressing from periphery of tubule towards lumen:
   1. Spermatogonia:  small nuclei, dense, strongly basophilic, coarsely clumped, compact chromatin.
   2. Spermatocytes:  large cells with large nuclei containing distinct, striated (coiled?) prophase chromosomes, prominent nucleoli and scattered mitochondria.
   3. Dividing spermatocytes:  rare; large cells, metaphase or anaphase configurations, clumps of chromosomes.
   4. Spermatids: small round nuclei, some with nucleoli (early), others with acrosome forming on nuclear surface as spherical or conical (later) cap.
   5. Early sperm: elongate, strongly basophilic head (nucleus) which is scimitar-shaped and dominated by hooked acrosome; flagellum with basal body and tail extending into lumen; developing mid-piece in which mitochondria can be seen in various stages of alignment around flagellar shaft; developing sperm with clearly excess cytoplasm (what happens to it?).
   
   
4. Sertoli cells:  large, pale nuclei often with prominent nucleoli, cell boundaries indistinct; what is their relationship to spermatogenic cells?

Webslide 0088_M:  Epididymis, monkey, Orange G stain  [DigitalScope]

Note the following:

1. Small bore tubules of the efferent ducts (ductuli efferentes) with epithelial cells of different heights (note tufts of cilia: compare their height with clumps of epididymal stereocilia).


2. Large bore ducts of the epididymis, some containing sperm.


3. Pseudostratified epithelium of the epididymis, composed of basal and columnar cells.  The latter display clumps of stereocilia.


4. Smooth muscle surrounds the tubules but is more prominent around the tubules of the epididymis.

Webslide 0089A_M:  Vas deferens, human, H&E  [DigitalScope]

Webslide 0089B_M:  Vas deferens, human, 19 yr. M, H&E  [DigitalScope]

Although both slides are from the vas deferens, one is taken from the proximal duct while the other is taken from the distal portion near the seminal vesicles. Which slide is taken from which portion of the vas deferens? How can you tell?

Note the following:

1. Three robust layers of smooth muscle at the start of the vas deferens.
2. Folded mucosa made up of pseudostratified columnar epithelium containing clumps of stereocilia (which may or may not be well preserved).

Webslide 0090_M:  Seminal vesicle, monkey, H&E  [DigitalScope]

Note the following:

1. Folded sacs cut in various aspects giving a unique appearance to this secretory mucosa.  Understand the 3-dimensional organization of blind diverticula that results in this appearance in sections. (See Junquiera fig 21-14).


2. Pseudostratified or simple columnar epithelium at various locations in this gland.


3. Connective tissue stroma and both circular and longitudinal smooth muscle.

Webslide 0054_M: Seminal vesicle, human, 19 yr., Mallory trichrome  [DigitalScope]

Use this slide to study the same aspects of the seminal vesicle as you did for Webslide 90. However, in this slide the smooth muscle is much more obvious due to the staining.

Webslide UMich 281:  Prostate, human, H&E  [DigitalScope]

The prostate in an adult is about the size and shape of a chestnut and contains 15-30 tubuloalveolar glands that empty separately into the prostatic urethra. The most important structures to see on the slide are the prostatic glands that are present over most of the section. The glands are embedded in a fibromuscular stroma that includes abundant smooth muscle. The epithelium of the glands is simple or pseudostratified columnar (there may be a few basal cells), and the cells differ greatly in height to give the epithelium a folded appearance. The prostatic urethra can also be seen (it has a stratified epithelium several cells thick and numerous mucosal glands). Also present is the prostatic utricle flanked by paired ejaculatory ducts.

With these landmarks, one can identify the various zones of the prostate that are clinically relevant in their propensity to become hyperplastic and/or cancerous:

1. The peripheral zone contains the main glands located posterio-laterally in the outer parenchyma of the gland and is the site most susceptible to inflammation (prostatitis) and malignant neoplasia (prostatic carcinoma).
2. The central zone is the region surrounding the utricle and ejaculatory ducts. Interestingly, this zone is relatively resistant to inflammation and hyperplasia.
3. The transitional and periurethral zones surrounds the prostatic urethra and contains submucosal and mucosal glands that undergo non-cancerous proliferation, leading to benign prostatic hypertrophy (BPH), a condition that effects almost all males to some extent by age 80. Typically, the submucosal glandsundergo hypertrophy first followed by the mucosal glands as the condition progresses.
4. The anterior fibromuscular stroma is located anteriorly and contains no glandular tissue so it typically does not become hyperplastic.

Webslide UMich 282:  Prostate, human, H&E  [DigitalScope]

Use this slide to examine the tubuloalveolar structure of the prostate glands, the smooth muscle between the glands, and at the concretions that are commonly seen within these glands.

Webslide UMich 286:  Glans penis, human, H&E  [DigitalScope]

Note the following:

1. Urethra with both stratified squamous and transitional epithelium present.
2. Corpus spongiosum, consisting of distended vascular spaces surrounding the urethra.
3. Portions of the corpora cavernosa, two masses of erectile tissue on the dorsal side.

PATHOLOGY CORRELATE

CASE NUMBER 5 (slide courtesy of UIowa)
[DigitalScope]

Clinical History: A 77-year-old man went to his primary care physician for an annual checkup. Digital rectal exam revealed a firm nodule at the base of the prostate gland. Serum PSA was measured at 7.0 ng/mL (normal < 4.0 ng/mL). Needle biopsies were performed and histopathology showed the presence prostatic adenocarcinoma with a Gleason grade of 3+4. The patient subsequently underwent a total prostatectomy.

(1) Features that confirm this is a prostate specimen:

The more normal part of the gland is in the lower left portion of the specimen. This organ combines a fibromuscular (bright pink, elongated cells, organized in sweeping bundles) with elaborately scalloped glands, some of which contain pinkish, flocculent secretions; and more elongated ducts. Close view of the gland lining epithelium shows columnar secretory cells with a "bubbly" cytoplasm and a "frayed" apical surface, indicative of apocrine secretion. At the top of the picture, we see a pinkish band of condensed fibrous tissue, outside of which fat, vessels and nerves are visible; this is the capsule.

(2) Features consistent with a diagnosis of prostatic adenocarcinoma:

Almost the entire upper half of the image and a good proportion of the lower half of the picture is comprised of a proliferation of small, simple glands with attenuated lumina, packed closely and with no acinar organization. They insinuate between normal (larger) glandular structures and in most of the upper half of the image entirely overrun them. They exhibit a high nuclear-cytoplasmic ratio (thus appearing "dark" at low power), have little secretory activity, and many have simple, circular profiles. At high power, the nuclei are significantly larger than those of the benign glandular epithelium in the lower half of the image; the chromatin is dark and granular; and many have abnormally prominent, central nucleoli with perinucleolar clearing. Finally, the presence of perineural and perivascular invasion is clearly in evidence. This is a useful diagnostic characteristic of adenocarcinoma of the prostate.

(3) Feature consistent with the Gleason grade of 3+4=7:

The Gleason grades are as follows:

Commonly, the Gleason grading system employs two grades with the primary Gleason pattern listed first and the secondary pattern listed second. This tumor is graded 3+4=7.

The hallmarks of Gleason 3 cancer are that it is (1) infiltrative, forming not a discrete nodule with identifiable borders, but rather infiltrating between and among benign glands; (2) comprised of tubular glands that in cross-section present as simple, rounded, single-lumen glands around which it is possible to mentally "draw" a circle within the intervening stroma clearly and entirely separating each gland from its neighbor. The majority of the cancer in this specimen meets these criteria, hence this is the primary Gleason pattern.

The hallmarks of Gleason 4 cancer are that it is (1) comprised of glands that have lost contact dependence on stroma, and so exhibit complex internal patterns including glands that appear "fused" without intervening stroma, glands that contain complex cribriform patterns comprising multiple lumina within a single gland, glands with more complex external profiles than the simple circular profiles of Gleason 1–3. Lumina are present, but tend to be smaller and subtler than in Gleason 3, as if the epithelium was starting to "forget" how to make well-formed lumina.  To mentally draw a circle around each single-lumen gland, entirely tracking intervening stroma, is impossible because of the fusion of the glands. Perhaps 20% of this cancer has such features, making Gleason 4 the secondary pattern.

Practice Questions

1. What is the main role of Sertoli cells in the testis?

1. Testosterone production
2. Maintenance of the blood-testis barrier
3. Transport of spermatozoa
4. Phagocytosis of spermatogenic cells
5. Secretion of fructose

[ANSWER]

2. The epithelial lining of the rete testis primarily consists of:

1. Simple squamous epithelium
2. Simple cuboidal epithelium
3. Stratified columnar epithelium
4. Pseudostratified epithelium with cilia
5. Transitional epithelium

[ANSWER]

3. The seminal vesicles secrete fluid rich in:

1. Mucus
2. Fructose
3. Proteins
4. Enzymes
5. Lipids

[ANSWER]

4. A 58-year-old man presents to his primary care physician with a cheif concern of frequent urination and is diagnosed with benign prostatic hyperplasia. In which histological zone of the prostate does this hyperplasia typically occur?

1. Peripheral zone
2. Transitional zone
3. Central zone
4. Anterior fibromuscular stroma
5. Medial zone

[ANSWER]

5. A 16-year-old boy is being evaluated for hypogonadism. Histological analysis of his testis reveals reduced Leydig cell function. Lab tests would also most likely find low levels of which of the following?

1. Testosterone
2. Estrogen
3. Progesterone
4. Inhibin
5. Activin

[ANSWER]

Organ Review

0153 [DigitalScope]

Identify as specifically as possible the organ shown in the slide AND provide at least FOUR specific or characteristic features (e.g. specific cell types and/or arrangements of cells/tissues in the organ) supporting your identification. For EACH feature listed, provide a brief explanation regarding its functional significance and/or how that feature is helpful in terms of distinguishing the organ.

[ANSWER]

Extra Slides

I. TESTIS

270 testis, human, H&E [Orientation]  [DigitalScope]
270ex testis, human, H&E [Orientation]  [DigitalScope]
UCSF 363 testis, hamster, Gomori [DigitalScope]
Webslide 0042_M:  Testis, monkey, 1.5 µm, H&E  [DigitalScope]

These slides (except for the UCSF slide and Duke Webslide) include both testis and epididymis (you will study epididymis later in this laboratory session): the testis is the larger of the two structures on the slide. The capsule of the testis is composed of dense connective tissue and is called the tunica albuginea. Within the testis you will see numerous profiles of seminiferous tubules, with interstitial tissue between them. In the interstitial tissue between the seminiferous tubules are clusters of Leydig cells, which secrete the male steroid hormone, testosterone. These are the most prominent cells in the interstitial tissue (best seen in #270 [example], or #275 [example]). Also visible in the interstitial tissue are blood vessels and smaller cells characteristic of loose connective tissue.

Now take a closer look at the the seminiferous tubules in #270  [example] [Orientation] or #270  [example] [Orientation] (in some of the seminiferous tubules the epithelium may be pulled away somewhat from the basement membrane, leaving a white space, which is an artifact). Each seminiferous tubule is surrounded by a boundary layer or tunica propria, composed of flattened cells, several cells thick. Most of the cells that lie against the basement membrane and have round nuclei are spermatogonia. Don’t worry about distinguishing between type A and type B spermatogonia. Now look for considerably larger nuclei midway up in the epithelium that are also round and are filled with a tangle of dense chromosomes. These are the nuclei of relatively mature primary spermatocytes, which are in the extended prophase of the first meiotic division. These are numerous but unfortunately not always well preserved (the nuclei may be somewhat swollen or distorted).

All of the smaller cells in the upper half of the epithelium (toward the lumen of the tubule) are spermatids in various stages of differentiation into mature sperm. The spermatids initially have round nuclei, but these gradually become smaller, denser and assume the shape of sperm heads. The smallest black structures you see are the heads of mature spermatids about to be released into the lumen. Their tails are difficult to make out.

Now look for Sertoli cell nuclei, which are large, relatively pale and irregular in shape, and contain a prominent nucleolus (sometimes out of the plane of section). Their nuclei commonly occur just above (toward the lumen from) the spermatogonia. Secondary spermatocytes are rarely seen, since almost immediately after they arise they undergo the second meiotic division to become spermatids. If you are anxious to see secondary spermatocytes, find division figures and look around them for nuclei that are intermediate in size between those of primary spermatocytes and spermatids. They are hard to find, so don’t spend much time looking. How can you differentiate between Sertoli cells, spermatogonia and primary spermatocytes?

II. MEDIASTINUM and EPIDIDYMIS

270 testis, human, H&E [Orientation]  [DigitalScope]
270ex testis, human, H&E [Orientation]  [DigitalScope]

Returning to the slides of the seminiferous tubules, study the passageway by which the sperm pass from the seminiferous tubules through the rete testis, efferent ducts and epididymis to reach the tail of the epididymis, where they are stored in preparation for an ejaculation. Scan along the tunica albuginea of the testis, looking for a region where it thickens and is permeated by a network of flattened channels in the dense connective tissue. This portion of the testis is known as the mediastinum; the network of channels is the rete testis and is probably best seen in slide #270. Observe that the rete testis is lined with a cuboidal (or sometimes low-columnar) epithelium and you may see occasional microvilli. (Purely as an aside, these cells also have a single or “primary” cilium. Obviously, these cilia don’t contribute much in the way of helping to propel sperm through the channel. Instead, they may function as chemoreceptors allowing the lining cells to monitor and modify the luminal contents).

The sperm leave the testis by means of these channels to reach the efferent ducts. However, for now, shift your attention outside the testis to the part of the epididymis that is included in this slide. You will see numerous sections through the long and convoluted duct that makes up the epididymis apparent in #270 [CAVEAT] . The epithelium of the duct is pseudostratified columnar. The tall epithelial cells have long microvilli on their apical surface (sometimes called “stereocilia”, although they are not cilia at all). You may be able to make out a thin layer of smooth muscle around the tubules, which presumably acts by peristalsis to move the sperm along.

Now scan over the section looking for tubules of the efferent ducts, which connects the rete testis to the epididymal duct. The efferent duct tubules are often (but not always) smaller than epididymal tubules, and their epithelium varies considerably in height, giving the tubule lumen a characteristic irregular or “star” shape. The epithelium is generally simple columnar, and consists of two cell types, taller cells have with cilia and shorter cells without cilia. The efferent duct is the only portion of the male tract displaying true, motile, cilia. These tubules may also have a thin layer of smooth muscle around them. Efferent ducts can be seen in slide #270 in a small region amongst the epididymis.

III. SPERMATIC CORD

284 spermatic cord H&E  [DigitalScope]

This is a cross section through a spermatic cord, such as you will see in the gross anatomy laboratory. On one side of the section you will see a cross section of the ductus (or vas) deferens [example], which has a circular lumen, lined by a pseudostratified epithelium and surrounded by a very thick wall of smooth muscle. Elsewhere you will see sections through two or more branches of the testicular artery, surrounded by connective tissue that contains numerous veins of the pampiniform plexus [example] (the veins are rather flattened and contain dark red blood). What is the function of the pampiniform plexus? 

The testicular artery has a typical internal elastic membrane and prominent circular smooth muscle coat (comprising the tunica media). The veins of the pampiniform plexus lack the internal elastic membrane, and their walls are somewhat less muscular. The blood in the vessels may have black particles in it, an artifact of the fixation procedure. The association of the veins of the pampiniform plexus with the testicular artery constitutes a countercurrent exchange system to cool the blood somewhat on its way to the testis. In the connective tissue you will find nerves and, around the periphery of the section, some cross-sectioned bundles of smooth (dartos) [example] and skeletal (cremaster) muscle [example].

IV. SEMINAL VESICLE

075 seminal vesicle H&E  [DigitalScope]
279 seminal vesicle H&E  [DigitalScope]

These are cross sections through a seminal vesicle, which you may remember from gross anatomy is a rather sacculated and contorted tube (slide 75 is also the slide we used to study parasympathetic ganglia, which are readily observable in the wall of this organ). Study the section with your light microscope, noting the moderately-abundant smooth muscle in the wall. The epithelium of this gland lies on the surface of interconnecting mucosal folds that extend into the lumen from the muscular wall. The sparse connective tissue within the folds constitutes the lamina propria of this mucosa. The epithelium, which may be either simple columnar or pseudostratified columnar, produces a secretion (including fructose, ascorbic acid and other components) which is expelled from the gland by contraction of the muscular wall during ejaculation, constituting about 50-80% of the semen.

V. PROSTATE GLAND

UMich 281-1ex prostate Masson   [DigitalScope]
UMich 281-2ex prostate H&E  [DigitalScope]

The prostate in an adult is about the size and shape of a chestnut and contains 15-30 tubuloalveolar glands that empty separately into the prostatic urethra. The most important structures to see on the slide are the prostatic glands that are present over most of the section. The glands are embedded in a connective tissue that includes abundant smooth muscle, best appreciated in the trichome-stained section (recall that collagen fibers will stain blue-green whereas smooth muscle is pink with deep red nuclei), which produces the pulsations of the prostate that expel the content of the glands during ejaculation. The epithelium of the glands is simple columnar (there may be a few basal cells), and the cells differ greatly in height to give the epithelium a folded appearance. The epithelial cells secrete various components of the semen (including citric acid and acid phosphatase).