Please ans the que given below:

Asked by  | 17th Aug, 2009, 06:54: PM

Expert Answer:

Each testis is packed with seminiferous tubules where spermatogenesis occurs.

The walls of the seminiferous tubules consist of diploid spermatogonia, stem cells that are the precursors of sperm. Spermatogonia  divide by mitosis to produce more spermatogonia or differentiate into spermatocytes.

Meiosis of each spermatocyte produces 4 haploid spermatids. This process takes over three weeks to complete.

During spermiogenesis, the spermatids begin to grow a tail, and develop a thickened mid-piece, where the mitochondria gather and form an axoneme. Spermatid DNA also undergoes packaging, becoming highly condensed. The resultant tightly packed chromatin is transcriptionally inactive. The Golgi apparatus surrounds the now condensed nucleus, becoming the acrosome. One of the centrioles of the cell elongates to become the tail of the sperm.

Maturation then takes place under the influence of testosterone, which removes the remaining unnecessary cytoplasm and organelles. The resulting spermatozoa are now mature but lack motility, rendering them sterile. The mature spermatozoa are released from the protective Sertoli cells into the lumen of the seminiferous tubule in a process called spermiation.

The non-motile spermatozoa are transported to the epididymis in testicular fluid. While in the epididymis the spermatozoa gain motility and become capable of fertilisation.

Answered by  | 18th Aug, 2009, 01:46: PM

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