Spermatogenesis

Lore & Background

Spermatogenesis starts with mitotic division of spermatogonial stem cells near the basement membrane of seminiferous tubules. These divisions produce type A cells (replenishing stem cells) and type B cells, which differentiate into primary spermatocytes. Each primary spermatocyte undergoes meiosis I to form two secondary spermatocytes, which then undergo meiosis II to produce four haploid spermatids. Spermatids are transformed into spermatozoa via spermiogenesis, involving tail formation, DNA packaging with protamines, and acrosome development. The process occurs asynchronically, with different maturation states observable in a transverse section of a tubule, termed a spermatogenic wave.

Reader's Guide

Spermatogenesis is fundamental to sexual reproduction, producing haploid male gametes that combine with female oocytes to form a diploid zygote. Chromosomal abnormalities from incorrect spermatogenesis can lead to congenital defects (e.g., Down syndrome, Klinefelter syndrome) or spontaneous abortion. The process is temperature-sensitive, requiring testes to be 1°–8 °C cooler than body temperature. Sertoli cells provide structural and metabolic support throughout differentiation. DNA repair mechanisms, including homologous recombinational repair and non-homologous end joining, help maintain genome integrity. The protein FMRP binds to meiotic chromosomes and regulates DNA damage response dynamics.

Did You Know?

• The process requires a temperature 1°–8 °C lower than normal body temperature of 37 °C (98.6 °F).
• Each primary spermatocyte gives rise to four spermatozoa through two meiotic divisions.
• Spermatogenesis starts during puberty and usually continues uninterrupted until death, with a slight decrease in quantity with age.