Slides:

m80 Testis and epididymis (human, demonstration slide)
s80 Testis (monkey)
s82 Spermatic cord (containing the ductus deferens)
s83 Prostate
s84 Seminal vesicle

Index of images

The male reproductive system consists of the testes (gonads), a conducting portion (extra-testicual excurrent ducts), a penis (copulatory organ) and associated glands. Within the testes the gametes are produced within the seminiferous tubules.  The seminiferous tubules are quite long structures (ca 50 cm) that are packed within lobules within the testis. The genesis and maturation of the gametes occurs primarily within the lumen of these tubules under hormonal (testosterone) stimulation from endocrine cells external to (within the interstitial tissue) the seminiferous epithelia. Also within the testes are the initial conducting portions of the system that includes the straight tubules (tubuli recti) and rete testis. The rete testis connect to the efferent ductules that exit the testis proper and connects to the epididymis at the head of the epididymis. In the human, there are about 500 seminiferous tubules/testis that empty into the labyrinth of the rete testis that connect to about 20 efferent ductules that connect to a single ductus epididymis at the head of the epididymis. This 5 m long, tubular element is highly convoluted and is found along the posterior aspect of the testis running from the top (head of epididymis) to the bottom (tail of epididymis) of the testis. The tail of the ductus epididymis connects to the ductus deferens at the base of the testis and the latter progresses back and becomes a component of the spermatic cord until it enters the abdomen. These ex current ductile elements have a smooth muscle wall for peristaltic propulsion of spermatozoa with this muscle wall increasing in thickness the more distant from the testis. The testis, epididymis, and proximal ductus deferens are housed within the scrotum and can be readily palpated if one finds a willing subject (so-called living anatomy). For the male, it can be done on oneself and scientifically justifies adjusting ones gonads. For the female, you will have to find a willing male subject and proceed with the utmost of scientific ethics. The ductus deferens terminates in an ampulla that is joined by the duct of the seminal vesicle to form the ejaculatory duct that joins the urethra within the body of the prostrate gland (prostatic urethra). The glands that empty their contents into the ex current system prior to the post-prostatic urethra contribute to the semen volume and contain elements that nurture the sperm on their honorable journey to fertilize the egg. The seminal vesicle is not a vesicle for semen as the name implies but secretes the major volume of fluid of semen. As noted above, it empties its products into the ampulla of the ductus deferens. The prostate empties it contents into the prostatic urethra. The glands that empty into the post-prostatic urethra are primarily involved in secreting a mucous that has a lubricating function and their secretions are released prior to ejaculation. These include the bulbourethral (Cowper's) glands that empty into post-prostatic urethra (specifically the membranous urethra) and the glands of Littre that are associated with the penile urethra. The epithelia lining the tubes of the system range from stratified to simple and low columnar to columnar with apical specializations (cilia, stereocilia, microvilli).

We begin our study of the male reproductive system with the testis. Study s80 (monkey testis) with the naked eye and you should observe a coat (tunica albuginea) surrounding a plethora of tubular elements, the seminiferous tubules. Study the section at low power and you will note the thick collagenous capsule, the tunica albuginea, with the numerous seminiferous tubules encased within it. If you are fortunate, and have lead a virtuous life, some portion of the tunica albuginea in your slide may be covered with a mesothelium (simple squamous epithelium) representing the visceral portion of the tunica vaginalis.  The seminiferous tubules are housed within lobules defined by connective tissue septa. The tubules present as a labyrinth of tubules showing longitudinal, cross, and tangential section of the tubes. Focus your study on the interstitial tissue and you will note a thin wall separating the individual tubules and junctional aggregates of cells where more than 2 tubules are adjacent. The thin layer contains capillary endothelial cells and the myoid cells. The junctional aggregates of cells contains the interstitial cells of Leydig that present with a round euchromatic nucleus and a lighter staining, vacuolated cytoplasm as would be suspected of this testosterone (steroid) secreting cell. Focus your study next upon the spermatogenic cells of the seminiferous tubule. You should observe tubules next to each other with similar nuclear morphologies at the base of the tubule but differing at the lumenal aspect. This is the result of the asynchronous spermatogenesis between the different regions of the tubules and even along the length of the same tubule. The net result of this is that you are not likely to see all of the stages to good example in a cross-section of a single tubule. Focus your study on one tubule and identify the cells (essentially the nuclei) of the epithelium. At high magnification, you observe that the most basal nuclei are those of spermatogonia with their very condensed chromatin within a small nucleus. Progressing further up, you will note an approximate layer of large nuclei with poorly packed chromatin, these are the nuclei of primary spermatocytes. Nearest the lumen are the smaller, pale staining nuclei that are those of the early spermatids. Note that the nuclei of most of the spermatogenic cells (excluding late spermatids) are round. You will also observe a large, oval very euchromatic nucleus with a prominent nucleolus and some apparent cytoplasmic eosinophilic staining that is the Sertoli cell or nurse cell for the spermatogenic cells. In the epithelium of another tubule, you may observe late spermatids with their spindle shaped nucleus with its highly condensed chromatin. The late spermatids are usually in groups, fitting with the local synchrony of spermatogenesis within a region of a tubule. The tails (flagella) of the spermatid my not be apparent but, if so, project into the lumen of the tubule. You may also note that a gaggle of spermatids appear to connect to the apical cytoplasm of an underlying Sertoli cell illustrating the nurse-cell function of the Sertoli cell. You may also observe some early spermatids with their small round nuclei, primary spermatocytes with their large nuclei, and at the base, you observe a large nucleus with dispersed chromatin and an obvious nucleolus. This is likely a spermatogonia type B. Examine the epithelia of other tubules and identify the cells.

We have thus studied the epithelia that gives rise to the late spermatids and will now trace the path of these through the ex current ducts. Return to low magnification and pan around the periphery of the testis. You may observe a region containing a series of canals lined with a thin epithelium. Emptying into these canals are the straight tubules (tubuli recti) of the seminiferous tubules; these are difficult to find and may not be present in your slide; ask a colleague for theirs. The tubuli recti are lined with Sertoli cells and connect the seminiferous tubule to the rete testis. The rete testis is lined with a simple low cuboidal to squamous epithelia cells that have a single cilium at their apex that is not apparent. There is a substantial layer of connective tissue beneath the epithelia relative to the seminiferous tubule epithelia.

To study the ex current ducts outside of the testis (extra-testicular), we will use a demonstration slide (m80) of the human testis and epididymis taken from a midline section of the posterior aspect of the testis. View the section with the naked eye and you will note the tunica albuginea separating the seminiferous tubules from the ex current ducts of the epididymis. Within the connective tissue around the ducts is a plethora of blood vessels involved in cooling the tubes of the system. The smallest of the extra testicular ex current ducts are the efferent ductules. The efferent ductules have a thin muscular wall and the lumen has a characteristic saw tooth appearance due to alternating groups of tall (ciliated) and short (microvilli) lining cells. The epithelia is pseudostratified columnar with obvious basal, cuboidal cells that are the stem cells. The proximal portion of the ductus epididymis has a larger diameter lumen with a smooth outline and a thicker muscular coat.  As the highly coiled ductus epididymis progresses from its proximal to its distal end, its lumen becomes larger and its muscular coats thicker.  Distally, the ductus epididymis is characterized by its large lumen and extremely thick muscular wall. The lining may have a few plica that project into the lumen; the plica are formed by projections of the mucosa (i.e., of the lamina propria and epithelium) . The epithelia presents as pseudostratified columnar epithelia with stereocilia. And again, you will note the cuboidal basal (stem) cells as observed in the efferent ductules. Distally, at the base of the testes the tail of the epididymis connects to and is continuous with the ductus deferens. 

The ductus deferens joins with the vascular and nerve supply of the testis and the cremaster muscle to form the spermatic cord and this can be observed in s82. Here, the smooth muscle wall of the ductus deferens is huge and is made of an inner longitudinal, middle circular and outer longitudinal layers of smooth muscle. The epithelia that lines the lumen is like that observed in the other regions of the ductus deferens but the plica are much more pronounced. You will also observe numerous blood vessels and nerve in the cord. The blood vessels include the testicular arteries that feed the testis and proximal ex current ducts and the pampiniform plexus of veins that drain these structures. These veins are much more numerous than the arteries and the venous wall is like that of the venae cavae in that they have a circular layer of muscle in the media and a longitudinal layer in the adventitia to facilitate (pump) the cooled blood from the testis and scrotum past the testicular artery to cool the arterial blood before it enters the testis. At or near the periphery of the cord, you may note skeletal muscle that is the cremaster muscle. This muscle, originating from the abdominal wall,  is attached to the cremasteric fascia and tunica vaginalis in which the testis, epididymis, and proximal ductus deferens are encased. This muscle relaxes when the ambient temperature is warm, allowing the testis to distend in the scrotum to facilitate cooling (hanging loose so to speak or of low testicular altitude) and conversely, contracts, pulling the testis up and closer to the abdominal cavity to keep them warm when ambient temperature is low (as when a male of the species takes a swim in cold water or of high testicular altitude). The dartos muscle within the dermis (the non arrector pili smooth muscle) of the scrotum also relaxes (increasing scrotal surface area) or contracts (decreasing scrotal surface area) to modulate heat loss. Note that testicular altitude does not present with bi-lateral symmetry. The left testis is usually 1 cm lower than the right (don't fret Cooter, it is normal).

We will next study two of the glands associated with the male reproductive system, the seminal vesicle and the prostate. The seminal vesicle is a tubuloalveolar gland that develops from an evagination of the ductus deferens which it joins at the ampulla to form the ejaculatory ducts. Study the seminal vesicle in s84 and at low power, you will note the alveolar nature of the gland and its muscular wall. The smooth muscle wall shows and inner circular and outer longitudinal layers of muscle. The secretory alveoli are open to a common tube although this in not apparent in sections of the gland. The simple cuboidal epithelia that lines the gland rest upon loose connective tissue (lamina propria), and the epithelia is made of mostly secretory cells that have an eosinophilic cytoplasm and pale staining, round, basal cells interspersed in the epithelium.

Lastly, we will study the prostate (s83). The prostate is also a tubuloalveolar gland. It is a complicated gland in that it essentially wraps around the urethra and empties its contents into the urethra; further,  the ejaculatory duct connects to the urethra within the prostate gland. As such, you may observe two lumens in the middle of the gland, the larger being the prostatic utricle and the smaller likely being an ejaculatory duct. Examine the section with the naked eye and you will observe at least one lumen and it is likely the prostatic utricle. Move away from this and study the other regions of the gland. You will note a fibromuscular coat surrounding secretory epithelia. Some features of the prostate relative to the seminal vesicle are that the prostate has smaller lumens and contains ovoid, amorphous eosinophilic structures within the lumen. These structures are called prostatic concretions (corpora amylacea). Further study the secretory epithelia and you will note that it is made of simple (mostly) columnar epithelial cells with pale staining cytoplasm. The fibromuscular stroma is more fibrous than muscular compared to the seminal vesicle which has an obvious muscular layer.

LAB:  Male Reproductive System