Figure 421 from Chapter 16 (Cytoplasmic matrix and cytoskeleton) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. Horizontal section through the apical cytoplasm of a Sertoli cell in the testis of the toad Buro marinus. Microtubules in these polarized cells are abundant and consistent in their orientation. The Sertoli cells serve as nurse cells for maturing spermatozoa, and late in sperm maturation, the sperm heads occupy deep recesses in the apical part of the Sertoli cells. A number of sperm at different levels are apparent in this section, surrounded by the cytoplasm of the Sertoli cell. A PDF copy of the accompanying chapter is available on the ASCB's BioEDUCATE website.