Spermatogenesis begins at -
Ans. is 'c' i.e., Puberty o Spermatogenesis refers to the process of formation of spermatozoa (sperm) from primitive germ cells (spermatogonia).o Spermatogenesis begins at puberty and continues throughout adult life to decline in old age.o In humans, it takes an average of 74 days to form a mature sperm from primitive germ cells.o Spermatogenesis occurs in seminiferous tubules.o Steps in spermatogenesis involve :i) Spermatogonia (primitive germ cells) undergo mitosis to form primary spermatocytes. Both spermatogonia and primary spermatocytes have diploid chromosomes (46 chromosomes or diploid of 23 chromosomes).ii) Primary spermatocytes undergo meiosis to form secondary spermatocytes. Secondary spermatocytes have haploid (23) chromosomes.iii) Secondary spermatocytes undergo mitosis to form spermatids.iv) Spermatids do not divide further but undergo morphological changes to form sperms (spermatozoa). This step of formation of spermatozoa from spermatids is called spermiogenesis. The spermiogenesis takes place in the deep folds of cytoplasm of sertoli cells.
Birth
5 years
Puberty
18 years
Fertilization and Development of Embryo