32.
Explain the process of spermatogenesis.
Formation of haploid spermatozoa from diploid soermatogonia is known as spermatogeneis. There are three primary phases - 1) Multiplication phase: the undifferentiated germ cells arise by mitotic division from the primordial germ cells of the germinal epithelium lining the seminiferous tubules. These are called soermatogonia. They are diploid and undergo mitotic division. 2) Growth phase: the type B soermatogonia(now termed as spermatocytes) grow in size, accumulate nutrients and replicate DNA. They are now termed as primary spermatocytes. 3) Maturation phase: Primary spermatocytes undergo first maturation division aka meiosis to form two haploid daughter cells called secondary spermatocytes. They undergo a second meiotic division and form four haploid daughter cells known as spermatids. Formation of Spermatozoa - The transformation of spermatids into spermatozoa is known as spermiogenesis. The changes which occur are - the nucleus shrinks; an acrosome is formed; axial filament is formed.
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