Plate 14.265 Seminiferous Tubule

Ronald A. Bergman, Ph.D., Adel K. Afifi, M.D., Paul M. Heidger, Jr., Ph.D.
Peer Review Status: Externally Peer Reviewed

In the seminiferous tubule, spermatogenic cells are arranged in orderly layers between the basement membrane and the lumen.

Spermatogonia: Located directly above the basement membrane. Spherical nucleus. Spermatogonia are the germ cells from which spermatozoa ultimately arise. They are the only sex cells present before onset of puberty. They contain 23 pairs of chromosomes.

Primary spermatocytes: Lie in the next layer, deep to the spermatogonia. Largest germ cells. Nuclei are large and vesicular with condensed chromatin. Chromatin may appear as elongated spiremes, i.e., irregularly disposed chromatin filaments. Primary spermatocytes divide by meiosis. Meiosis is nuclear division in which the diploid chromosome number (23 pairs) is halved to the haploid number (23 single set) in the formation of sex cells.

Round spermatids: Adjacent to the lumen. Small in size. Spermatids constitute the last stage in the transformation to spermatozoa.

Mature spermatids: Heads are located near Sertoli cells, and tails project into the lumen. Heads are transformed nuclei of round spermatids. Will be released into lumen as spermatozoa.

Sertoli cells: Supporting cells of the testicular epithelium, which were first described by the Italian physiologist Enrico Sertoli in 1865. Tall columnar cells extend from the basement membrane to the lumen. Nucleus ovoid in shape with prominent nucleolus. Cell borders are difficult to outline in this preparation.

The process of spermatogenesis from spermatogonia to mature spermatozoa requires about 64 days in man.

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