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Click any cell to select it. Stages run left to right (I–XIV in Roman numerals). Cycles run bottom to top — youngest cells at the bottom.
AsType A spermatogonia, stem cellAprType A spermatogonia, pairedAalType A spermatogonia, alignedA1Type A1 spermatogoniaA2Type A2 spermatogoniaA3Type A3 spermatogoniaA4Type A4 spermatogoniaIIntermediate spermatogoniaBType B spermatogoniaPLPreleptotene spermatocyteLLeptotene spermatocyteZZygotene spermatocytePPachytene spermatocyteDDiakinetic pachytene spermatocyteM1Meiosis 1 divisionSSSecondary spermatocyteM2Meiosis 2 divisionS1–S8Round spermatids (steps 1–8)S9–S19Elongating spermatids (steps 9–19)SSertoli cell✱Mitosis✱✱High mitotic activityAs, Apr, Aal = uncommitted spermatogonia that divide randomly to replenish the epithelium. Aal spermatogonia differentiate, forming committed A1 spermatogonia at Stage VIII that begin mitosis (✱) at Stage IX — this marks the start of cycle 1 of spermatogenesis. As cells synchronize with Stages VIII–IX in the rat (Abid et al. 2014); the interrupted dashes in the grid mean these cells may be present elsewhere but are most likely to be observed at the labelled positions. Total spermatogenesis ≈ 4.0 cycles (4 × 12.9 d ≈ 51.6 d).
The dark line is the basement membrane. All cells in the bottom three rows — committed spermatogonia (cycle 1: A4, I, B, early PL), the A1–A3 transition row, and the As/Apr/Aal stem-cell pool — actually rest directly on the basement membrane. The vertical separation between these rows in the grid is for organizational clarity (so you can click each cell type individually), not anatomical position. PL cells begin migrating through the Sertoli–Sertoli junctional barrier (blood-testis barrier) at Stage VIII; by Stage X the leptotene (L) cells are adluminal. Other cell types are drawn at approximate anatomical positions and proper cellular associations.
Colors group cells by role: uncommitted spermatogonia (As, Apr, Aal), committed spermatogonia (A1–A4, I, B), meiotic cells (PL, L, Z, P, D, M1, SS, M2), spermatids (S1–S19, magenta to match PAS acrosome staining). Single (✱) marks mitosis; double (✱✱) marks high mitotic activity.
Adjust cycle length, epididymal transit time, or per-stage percentages to model a different strain, breed, or experimental condition that uses the same grid layout. All updates apply live — the Days row, cell time bounds, and predictions recompute as you type.
When adjacent stages can't be distinguished (H&E stain, pathological changes, or coarser classification), define groups. A bracket bar appears above the grid showing each group's range and combined %.
Enter individual stage %s if known, or one per group if using grouped counting. For grouped counting, put the group total in the last stage of each group and 0.0 in the others. Then click Distribute group totals proportionally below — it spreads each group total across its stages using the species defaults, so predictions from any cell land at biologically plausible targets. Loading a preset (above) does both steps automatically. Values auto-normalize to sum to 100% internally.