Answer
After mitosis, the Type B spermatogonia enlarge and differentiate into primary spermatocytes. These cells are about to go through meiosis and become haploid cells with unique chromosome combinations; they therefore run the risk of being attacked by body antibodies as non-self cells. It is necessary for them to be segregated from blood plasma . This is effected by the opening of tight junctions between sustentacular cells. Passage of the primary spermatocytes (PSMs) into the lumens of the seminiferous tubules is facilitated by this process. After the primary spermatocytes have passed into the lumens(lumina), new tight junctions are reformed between sustentacular (Sertoli) cells, thus excluding them (PSMs) from the blood supply in the walls of the seminiferous tubules.
Work Step by Step
The next step in spermatogenesis is for the primary spermatocytes to undergo meiosis I. The result is two equal sized haploid cells with genetically unique nuclei. Each secondary spermatocyte undergoes Meiosis II--a mitotic division. The result is four spermatids (n) from each primary spermatocyte. At first, the products of spermatogenesis do not separate, but are connected for some time by thin cytoplasmic bridges. However, after spermiogenesis, the sperms separate from each other, and are moved down the tubular lumen by fluids.
