Spermatogenesis

Key points

• • It takes place in the seminiferous tubules and takes roughly 64 days from spermatogonium to spermatozoon.
• • Diploid spermatogonia multiply by mitosis, a primary spermatocyte then undergoes meiosis to give haploid spermatids, and these mature into spermatozoa in a step called spermiogenesis.
• • Sertoli cells nurse the developing cells, form the blood-testis barrier and are the target of follicle-stimulating hormone.
• • Leydig cells lie between the tubules and make testosterone in response to luteinising hormone; a high local testosterone level is essential for sperm production.
• • Developing germ cells carry antigens the immune system has not learnt to tolerate, so the blood-testis barrier sequesters them and maintains this immune privilege.
• • The process needs a temperature a few degrees below core body temperature, which is why the testes sit in the scrotum.