Male Genital System
Learning Objectives:
Describe the histological organizaiton of the testis and correlate it with function
Compare the features of Sertoli and Leydig cells and explain their role in testis-blood barrier maintenance and androgen production
Describe the histology of the male genital ducts and accessory glands while correlating location and function
SLU Slide 53: Testis ** preferred
Iowa Virtual Slidebox: Testis and rete (193)
Iowa Virtual Slidebox: Testis (259)
Testis
Beginning at low power and advancing to higher magnification, identify the tunica albuginea. How would you describe the tissue seen here? I.e., what kind of tissue is it?
It is thick layer of connective tissue.
Return to low power to observe the rest of the testis. You should see seminiferous tubules separated by interstitial tissue. Examine this tissue at higher power. What type of endocrine cell is found here? What hormone do they produce, and what is their distinguishing feature?
Leydig cells are the main endocrine cells of the testis and produce testosterone in response to LH. They have an eosinophilic cytoplasm.
Draw or take a screenshot of a cross section of a seminiferous tubule, including in your drawing a spermatogenic cell undergoing each phase of spermatogenesis. Note the criteria you use to distinguish each phase:
· Spermatogonia
· Primary spermatocyte (Where are they found? What are the threadlike structures you see within this cell and why do they exist in primary spermatocytes?)
· Secondary spermatocyte (Do you see these in your histological section? Why or why not?)
· Early Spermatids and late spermatids (Why are spermatids so variable in shape, size, and morphology? What process are they going through?)
Also include at least one Sertoli cell with its nucleus, and indicate how you can identify it as such.
Your cross section should include spermatogonia at the basal lamina of the epithelium surrounding the seminiferous tubule.
Primary spermatocytes should be closer to the lumen of the tubule, and have a larger nucleus. These cells are arrested in phase I of meiosis, so you may see condensed chromosomes in their nucleus.
Secondary spermatocytes are infrequently seen because they quickly complete the second meiotic division and become spermatids.
Spermatids are adjacent to the lumen, and are undergoing cytodifferentiation. You’ll see some spherical spermatids, and others in the shape of tadpoles.
Your Sertoli should extend all the way from the basal lamina to the lumen of your seminiferous tubule. Because Sertoli cells surround the other cells, their outline is difficult to discern. You should differentiate them based on their nucleus, which is are oval and have a prominent nucleolus.
No Slide
Describe the steps of spermatogenesis and spermiogenesis, including where each step occurs. At which stage is a sperm fully mature?
Refer to your lecture notes to discuss the three phases of spermatiogenesis and the four phases of spermiogenesis. A sperm is fully mature after the maturation phase, during which the amount of cytoplasm is drastically reduced.
Identify and draw a Leydig Cell and Sertoli cell. What is the function of each?
Sertoli cells provide mechanical and nutritive support to the surrounding spermatogenic cells. Leydig cells synthesize and secrete testosterone.
Iowa Virtual Slidebox: Testis and rete (193)
Describe the pathway a spermatozoa takes from the testis to the urethra:
Seminiferous tubules > Straight tubules > Rete testes > Efferent ducts > Head of epididymis > Body of epididymis > Tail of epididymis > Ductus deferens > Ampulla of ductus deferens > Ejaculatory duct > Urethra
Observe this slide at low magnification. Part of your field will have seminiferous tubules. The other part of your field will have an area with a dense bed of vascular tissue and empty channels. These are the rete testes. Observe at higher magnification. How do you describe the epithelium of these channels?
Simple cuboidal epithelium
Epididymis & Ductus Deferens
Iowa Virtual Slidebox: Epididymis (186)
Iowa Virtual Slidebox: Epididymis (260)
What happens to spermatozoa in the epididymis?
Sperm mature
Describe the epithelium of the epididymis.
Pseudostratified columnar epithelium with stereocilia
How can you distinguish between a seminiferous tubule and a transverse section of the epididymis?
Seminiferous tubules have a germinal epithelium that is stratified. The epididymis has a simple columnar epithelium with stereocilia. Don’t confuse the cilia of the epididymis with the tails of spermatids!
Iowa Virtual Slidebox: Vas deferens (261)
In these sections, note the prominent ductus deferens with a stellate lumen. What type of epithelium lines this lumen? How does this compare to the lumen of the epididymis?
The lumen is round in the epididymis but stellate and folded in the ductus deferens.
Identify the layers of smooth muscle surrounding the mucosa. How many layers are there, and what the orientation of each?
There are 3 layers of smooth muscle: Longitudinal, circular, and longitudinal. It may be difficult to discern these layers but give it a try!
Optional: Identify the additional structures of the spermatic cords present in these sections: Pampiniform plexus, cremaster muscle, and testicular artery.
Prostate Gland
Iowa Virtual Slidebox: Prostate (189)
Examine this slide, which contains two sections of the prostate gland, at low magnification. Observe the dense connective tissue covering the gland.
Moving toward the internal area of the gland, observe the alveoli of the prostate gland. What type of epithelium do they have?
The prostate gland has a simple cuboidal or columnar epithelium (as is found in many secretory organs).
Inside the some of the alveoli of the prostate, you can observe large structures with no cellular morphology. What are these? What is their relationship to age?
Corpora amylacea (aka Prostatic concretions) – they increase with age.
Seminal Vesicle
Iowa Virtual Slidebox: Seminal Vesicle (188)
Although the lumen of the seminal vesicle appears as separate cavities when sectioned, it is in fact one highly folded lumen. What type of epithelium lines this structure?
Simple columnar/ Pseudostratified columnar
The seminal vesicle has a prominent muscularis. With which other structure discussed today does it share that feature? From a developmental standpoint, why is that significant?
They share a thick muscularis with the vas deferens. This is significant as they are developmentally derived from the vas deferens.
In addition to the brownish/yellowish pigment visible in the SLU Slide (lipofuscin), there is an acidophilic secretion in the lumen of the vesicle. This secretion is rich in fructose.
Penis and Urethra
Iowa Virtual Slidebox: Penis (264)
Identify the corpus spongiosum by first identifying the intensely staining, folded penile urethra at its center. What type of epithelium does it have?
In the prostatic urethra (not shown here) the urethra is lined by a urothelium. In the membranous urethra, it is lined with stratified columnar epithelium. Further distally, the urethra is lined by stratified squamous epithelium.
Next, identify the paired corpora cavernosa. (Note that it may be difficult to identify them in this section. Refer to an atlas image if you have difficulty.)
Compare the venous sinuses in the corpus cavernosum to that of the corpus spongiosum. What other tissue exists in the structure of the penis?
In addition to vascular tissue, other tissues include dense connective tissue.
Note that neither of these sections were taken from human samples. You can tell from the keratinized spines (with underlying mechanosensory structures) emanating from the skin.
Iowa Virtual Slidebox: Penis and urethra (191)
These sections were taken from humans. Note the structure of the corpus cavernosum and corpus spongiosum.