Spermatogenesis

During human spermatogenesis, stem cells give within the testes give rise to functional sperm cells.

This process occurs within seminiferous tubules, muscle-wrapped structures that contain a peripheral layer of cells surrounding a hollow center. Importantly, the inner layer contains stem cells, each known as a spermatogonium, and supporting sertoli cells.

Factors produced during puberty, stimulate a spermatogonium to divide via mitosis. Of the two ensuing cells, one continues to serve as a stem cell, while the other is a precursor, that will ultimately go on to form sperm.

Multiple, subsequent mitotic divisions of this precursor cell, eventually result in a new type of cell, called a spermatocyte, located closer towards the interior of the tubule.

At this point, additional factors modulated by sertoli cells, direct spermatocytes to enter meiosis, causing them to divide twice, thus every spermatocyte produces four haploid cells, each containing a single chromosome set.

These haploid spermatids are situated at the boundary of the cell layer, and hollow core of the seminiferous tubule. As spermatogenesis proceeds, the spermatids lose cytoplasm, thin, and develop characteristic tails called flagella.

The resulting, differentiated sperm are then released into the tubules hollow center, and eventually make their way through the male genital tract.

Thus, the final outcome of spermatogenesis is numerous haploid, motile sperm cells, equipped to fertilize eggs.