A 35 year old male presents to the urologist for an infeility evaluation. A biopsy of his testis is performed to check sperm production and maturation. A microscopic section reveals only a few germ cells near the basal lamina in the seminiferous tubule. Which of the following cells is the germ cell closest to the basal lamina in the seminiferous tubule?: (A) Primary spermatocyte, (B) Secondary spermatocyte, (C) Spermatid, (D) Spermatogonia
Answer is D. Maturation of germ cells (spermatogenesis) within the seminiferous tubules occurs in a concentric pattern with the less mature spermatogonia near the basal lamina and the mature forms near the tubule center. Spermatogonia are 2N cells and mature into larger primary spermatocytes (4N) . These mature into secondary spermatocytes (2N) , and finally into spermatids (1N) . Spermatids undergo spermatogenesis to become mature spermatozoa . Acrosomes form from the Golgi apparatus and a flagellum forms from microtubules. Unneeded organelles are shed. The seminiferous tubules of a reproductive-age male should exhibit all stages of maturation, with mature flagellated sperm in their centers.