Slide #DMS 186 [Testis, human, H&E]. This slide is good for studying the general structure of the organ. Identify the following: tunica albuginea, seminiferous tubules, interstitial CT and interstitial (Leydig) cells. Reserve detailed study of the seminiferous epithelium for the next slide. In the H&E slide you will see the mediastinum testis with its epithelium-lined channels, the rete testis, into which the seminiferous tubules lead. The Masson-stained section provides a good view of the interstitial CT, blood vessels, and interstitial (Leydig) cells. In the latter, look for the crystals of Reinke which are peculiar to humans but of unknown significance. What hormone is produced by the Leydig cells and what hormone stimulates its synthesis and secretion?
Longitudinal section of testis, Epididymis, ductus deferens: 1. Ductuli efferentes; 2. Tubulus rectus; 3. Seminiferous tubule; 4. Interlobular septum; 5. Tunica albuginea; 6. Caudal epididymis; 7. Corpus epidiymis; 8. Mediastinum, rete testis; 9. Ductus deferens; 10. Caput epididymis.
This is a very low power view through a section of testis. A portion of the tunica albuginea, which encapsulates the organ, can be seen. Numerous fibrous septa extend from the tunica into the substance of the testis subdividing the organ into lobules.
A higher power view near the edge of the testis shows a portion of the tunica albuginea through which are traveling elements of the rete testis. Extending from the tunica, one can see connective tissue septa forming the walls of the lobules, with each lobule containing several seminiferous tubules, sections of which are seen in this image.
In this medium power image, one may see, with just a touch of imagination, the continuity of a seminiferous tubule with the tubuli recti (straight tubule) which drains it. The contents of the tubuli recti will flow next into the rete testis.
This image provides a higher power view of the simple cuboidal epithelium characteristic of the rete testis.
This is a low power view of a section through a portion of two lobules, separated by a connective tissue septum. Each lobule contains one to four tightly-packed and highly convoluted seminiferous tubules, numerous sections of which may be seen here. A highly vascular, loose connective tissue fills the space between the tubules.
At higher power, one may appreciate the complicated histological architecture of the seminiferous tubule, the details of which will be seen to better effect in subsequent specimens. The interstitial tissue intervening between tubule segments is home to the testosterone-producing Leydig cells which secrete their product into the numerous blood vessels of the stroma.
This is a very low power view through a section of testis stained with a Masson trichrome to highlight the connective tissue components. Connective tissue septa and the interstitial tissue in amongst the seminiferous tubules are stained a greenish-blue hue while the seminiferous tubules stain a reddish color.
This is a low power view through several seminiferous tubule sections and the interstitial tissue that separates them. Numerous blood vessels course throughout the interstitial tissue, and abundant Leydig cells, seen to better effect in the next image, also reside there.
At high power, one can begin to appreciate some of the details of the seminiferous tubule and the different stages of developing sperm cells found there including the basally-positioned spermatogonia, the large primary spermatocytes and spermatids in various stages of spermiogenesis. In the interstitial tissue, Leydig cells are distinguished by their large, euchromatic nuclei and prominent nucleolus. Note, again, the ever-present blood vessels typical of all endocrine organs, including the testis.
With oil immersion, the distinctive crystals of Reinke found within the cytoplasm of the Leydig cells are easily seen. Again, note the large, euchromatic nucleus and prominent and often eccentrically-located nucleolus typical of this cell type.
A close examination of the seminiferous tubules reveals the major cell types contributing to a rather complex epithelial architecture. The epithelium itself is established by the Sertoli cells, the only distinctive feature of which is their often angular nuclei highlighted by a prominent nucleolus. In close association with the cytoplasmic contours of the Sertoli cells may be found spermatogonia, primary spermatocytes (characterized by their condensed chromosomes), and spermatids in various stages of spermiogenesis.
An oil immersion view of the luminal surface of a seminiferous tubule again shows a primary spermatocyte and numerous spermatids in both the early and late phases of spermiogenesis. On the lip of the tubule one can see several nearly mature spermatozoa with their flagella extending into the luminal space.