Testosterone stimulates the secretion of growth hormone, resulting in a growth spurt, an increase in muscle mass, a higher metabolic rate, and a larger larynx. As testosterone levels decline, so does feedback inhibition of the pituitary. Consequently, FSH and ICSH levels rise significantly in the late 40s to early 50s, producing changes called male climacteric. The most significant event of puberty is the onset of spermatogenesis. In eukaryotes, there are two types of cell division - mitosis and meiosis.
Mitosis is the type of cell division used for growth and repair, as well as embryonic development.
The daughter cells are genetically identical to the parental cells. Parental cells and daughter cells are both diploid. Meiosis, sometimes called reduction division, produces 4 genetically variable, haploid cells, called gametes, that will go on to fuse with other gametes, and produce an entirely new genetic combination in a zygote. The penis is richly supplied with blood from an internal pudendal artery that divides into a dorsal artery and a deep artery within the root of the penis. The excitement phase is characterized by vasocongestion, myotonia, and increases in heart rate, blood pressure, and pulmonary ventilation.