spermatogenesis

spermatogonia

most primitive male germ cells located in basal compartment of seminiferous tubules; undergo mitotic divisions to produce primary spermatocytes

primary spermatocytes

male germ cells derived from final mitotic division of spermatogonia; undergo Meiosis I to produce secondary spermatocytes

secondary spermatocytes

created via Meiosis I of primary oocytes, undergo Meiosis II

spermatids

haploid male germs cells derived from secondary spermatocytes that undergo differentiation from round spermatid to fully developed spermatozoa; most vulnerable to heat/cold stress

Sertoli cells

analogous to female’s granulosa cells; contain FSH and testosterone receptors, form blood-testes barrier, secrete androgen-binding protein (inside SFs)

Leydig cells

analogous to female’s Theca cells; stimulated by LH to produce testosterone (outside SFs)

myoid cells

muscle fibers that move sperm through SFs via peristaltic contractions (outside SFs)

proliferation phase

mitotic divisions of spermatogonia/spermatocytogenesis; some cells regenerate spermatogonia, some go on to Meiosis; length of 21 days in bull

meiosis I

guarantees genetic diversity, 21 days in bull

meiosis II

makes sperm cells haploid, 2 days in bull

differentiation

spermiogenesis; round to fully formed spermatids, 17 days in bull

61 days

total number of days for spermatogenesis