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Process that occurs in the testicles, the male gonads. They secrete testosterone, the sex hormone responsible for the onset of male sexual characteristics: increased beard and body hair, more developed muscle mass, severe voice tone, etc.
The cells of the testes are organized around the seminiferous tubules in which sperm are produced. Testosterone is secreted by interstitial cells. Surrounding the seminiferous tubules are the Sertoli cells, which are responsible for nourishing and sustaining germline cells, that is, those that will generate sperm.
In mammals, the testicles are usually outside the abdominal cavity in a skin pouch called the scrotum. Thus, the temperature of the testicles remains approximately 1 ° C below body temperature, which is ideal for spermatogenesis.
Spermatogenesis is divided into four phases:
Proliferation or multiplication phase: It begins at puberty and occurs continuously throughout the life of the individual. The primordial cells of the testicles, diploids, increase in quantity by consecutive mitoses and form the spermatogonia.
Growth stage: A small increase in the cytoplasm volume of spermatogonia converts them into first order spermatocytes, also called primary spermatocytes or spermatocytes I, also diploid.
Maturation phase: It is also rapid in males and corresponds to the period of meiosis occurrence. After the first meiotic division, each first-order spermatocyte gives rise to two second-order spermatocytes (secondary spermatocytes or spermatocytes II). As a result of the first division of meiosis, they are already haploid, although they have duplicate chromosomes. With the occurrence of the second meiotic division, the two second order spermatocytes give rise to four haploid spermatids.
Spermogenesis: It is the process that converts spermatids into sperm, losing almost all cytoplasm. Golgi complex vesicles fuse to form the acrosome located at the anterior end of the sperm. Acrossome contains enzymes that pierce egg membranes during fertilization.
Centrioles migrate to the region immediately posterior to the spermatid nucleus and participate in the formation of the flagella, a structure responsible for sperm movement. Many mitochondria, responsible for cellular respiration and ATP production, are concentrated in the region between the head and the flagella, known as the intermediate piece.