![]() ![]() The smallest black structures you see are the heads of mature spermatids about to be released into the lumen. The spermatids initially have round nuclei, but these gradually become smaller, denser and assume the shape of sperm heads. 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. These are numerous but unfortunately not always well preserved (the nuclei may be somewhat swollen or distorted). These are the nuclei of relatively mature primary spermatocytes, which are in the extended prophase of the first meiotic division. Now look for considerably larger nuclei midway up in the epithelium that are also round and are filled with a tangle of dense chromosomes. Don’t worry about distinguishing between type A and type B spermatogonia. Most of the cells that lie against the basement membrane and have round nuclei are spermatogonia. Each seminiferous tubule is surrounded by a boundary layer or tunica propria, composed of flattened cells, several cells thick. Now take a closer look at the the seminiferous tubules in slide 270 View Image (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). Also visible in the interstitial tissue are blood vessels and smaller cells characteristic of loose connective tissue. These are the most prominent cells in the interstitial tissue, but in slide 270 of some slide sets, the Leydig cells slide 270 View Image are not seen very clearly (in that case, see them in slide 275 View Image). In the interstitial tissue between the seminiferous tubules are clusters of Leydig cells, which secrete the male steroid hormone, testosterone. Within the testis you will see numerous profiles of seminiferous tubules, with interstitial tissue between them. The capsule of the testis is composed of dense connective tissue and is called thetunica albuginea. ![]() These slides (except for the UCSF slide) 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. Slide 273 Testis H&E immature View Virtual Slide Slide UCSF 363 testis View Virtual Slide (virtual slide courtesy of the University of California, San Francisco) Slide 270ex testis H&E View Virtual Slide Slide 270 testis testis H&E View Virtual Slide ![]()
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