Figure 2.

Stages 1–9 of the seminiferous epithelium cycle on the tubular morphology system. Abbreviations of germ cells are as follows: Ad (dark type spermatogonia), Ap1 (pale type spermatogonia), Ap2 (pale type spermatogonia), B type B spermatogonia, L (leptotene primary spermatocytes), P (pachytene primary spermatocytes), Z (zygotene primary spermatocytes, Dp (diplotene primary spermatocytes), Pe (peritubular myoid cell) and S (Sertoli cell). Scale bar = 20 µm. Stage 1: (a) this stage was identified by the presence of the earliest generation of spermatids at step 1 of spermiogenesis. Step 10 spermatids were clustered in groups embedded in the Sertoli cell cytoplasm. Primary spermatocytes were observed in the early leptotene and zygotene stages and they were scattered between spermatogonia and spermatids. During the development of spermatocytes, the nuclei of primary spermatocytes were morphologically larger and they contained dark stained chromatin strands twisted together. Two types of spermatogonia, the pale type Ap1 and dark type Ad, were located on the basement membrane. Type Ap1 spermatogonia were identified by the presence of chromatin particles having some larger and smaller clumps. Type B spermatogonia were identified by the presence of clumps of chromatin and hugging the basement membrane. Staining density of type B spermatogonia was intermediate between the dark Ad and pale type Ap1 spermatogonia. Stage 2: (b) as described above, stained granules were seen in the cytoplasm at stage 2. All other germ cells were the same as in stage 1 (a). Stage 3: (c) spermatids at this stage had become slightly oval in shape, lost their cytoplasm and became shortened. Mature spermatids were seen at this stage ready for spermiation. In the second row, leptotene spermatocytes were present whereas in the third and fourth row zygotene spermatocytes were observed. Spermatogonia were present near the basal membrane. Stage 4: (d) this stage was identified by the presence of step 4 spermatids. In the second row, leptotene primary spermatocytes were present. Step 10 spermatids were observed moving towards the luminal border. Between the third and fourth germ cell layers, pachytene spermatocytes were observed. Spermatogonia Ad, Ap2 and B lined the basal membrane. Stage 5: (e) the presence of Stage 5 spermatids confirmed this stage in which spermatids had a bigger acrosome, thickened nuclear membrane depicting a larger area of attachment than previous spermatids generations. The other germ cell types remained the same. Stage 6: (f) this stage was characterized by the existence of step 6 spermatids. Stage 6 spermatids exhibited specific nuclear morphological changes in which the cell nucleus almost vanished and the cell became elongated in shape. The spermatid head was observed protruding out oriented towards the basement membrane. Spermatogonia B lined near the basement membrane. Leptotene primary spermatocytes and pachytene primary spermatocytes were observed concomitantly in succeeding seminiferous epithelial layers. Stage 7: (g) in this stage the spermatids were observed in the cylindrical and more elongated shape having a spiral chromatin material wrapped along the stage 7 spermatid like helix. Stage 7 spermatids are slimmer than the previous stage spermatids. Due to acrosome elongation, cells seemed more wide morphologically. Pachytene, leptotene primary spermatocytes and spermatogonia Ad were observed as before in the subsequent layers. Stage 8: (h) the presence of stage 8 spermatids confirmed stage 8 of the seminiferous epithelium. The diameter of the cell as well as the nucleus further reduces. The nuclear chromatin condenses into coarse, round or oval shaped granules. Spermatids at this stage were observed in moving towards the lumen of the seminiferous epithelium. Other germs cells, i.e., primary spermatocytes in pachytene and leptotene stages were observed. Spermatogonia B lined the basement membrane. Stage 9: (i) at this stage spermatids were quite matured and hanging out near the lumen of the seminiferous epithelium. This stage was identified by the presence of stage 9 and 10 spermatids. These spermatids were observed in clusters and were less spiral in shape. First meiotic division gives rise to two haploid spermatocytes from a single diploid spermatocyte. Diplotene primary spermatocytes emerged as a result of the first meiotic cell division in which degradation of the synaptonemal complex can be observed. Leptotene primary spermatocytes form the next layer. Dark spermatogonia Ap1, pale spermatogonia Ad and B spermatogonia lined the basement membrane.