Spermatogonium
The cell you are examining is a spermatogonium (answer d). Spermatogonia are the undifferentiated germ cells located at the periphery (basement membrane) of seminiferous tubules with characteristically round nuclei 1, 2.
Anatomical Location and Morphology
- Spermatogonia reside at the basal compartment of the seminiferous tubule, positioned directly against the basement membrane at the periphery 1, 3
- These cells possess round nuclei, which is a defining morphological characteristic that distinguishes them from other germ cell types 1, 2
- The peripheral location is critical because spermatogonia represent the stem cell population that maintains spermatogenesis throughout reproductive life 2
Why Other Options Are Incorrect
- Sertoli cells (option a) are somatic support cells, not germ cells, and while they are also located at the periphery, they have irregular nuclei with prominent nucleoli and extend from the basement membrane to the tubular lumen 4, 5
- Spermatids (option b) are post-meiotic haploid cells located in the adluminal compartment near the tubular lumen, not at the periphery 1, 3
- Leydig cells (option c) are located in the interstitial space between seminiferous tubules, not within the tubules themselves 6
- Primary spermatocytes (option e) are larger cells that have moved away from the basement membrane into more central positions within the seminiferous epithelium as they undergo meiosis 1, 3
Spermatogonial Classification
- In humans, spermatogonia are classified as either A-dark (reserve stem cells) or A-pale (active self-renewing stem cells), both maintaining their position at the tubular periphery 2
- In rodents, the classification is more complex with A-single, A-paired, A-aligned, A1-A4, intermediate, and type B spermatogonia, but all originate from the basal location 1, 2
- Type A spermatogonia serve as the stem cell reservoir, undergoing mitotic divisions to maintain the germ cell population 1, 2