All people and animals have gender - male or female. A person's sex is determined at the moment of his appearance - when mom's sex cell (egg) is connected with my father's sex cell (sperm). And then the man begins to grow and develop clear program. This program, among other things, to determine how to develop boys and girls.
The structure of the testis of man.
The testis and epididymis are in a leather pouch - the scrotum.
The testicles in boys begin to form as early as the second month of pregnancy mothers, when the length of the body of the child (embryo) is only 3-3 .5 cm. It is in the testes are formed substances that make the baby boy. These substances are called hormones.
Since 12-13 years, hormones trigger the process of puberty, in which the boy becomes an adult man.
Male sex hormones called androgens. The primary male sex hormone - testosterone.
In the same age group (12-13 years) in the testes begins the process, which then continues throughout the life of an adult male. This process is the formation of male gametes. They are called sperm, and the process of their education - the spermatogenesis. Sperm cells are those cells that, connecting with the female sex cells - eggs - give a new beginning.
Thus, the testicles are organs that make a man a man and responsible for procreation.
By the way ...
And the girls have testicles?
Yes, girls have a similar paired organs. She called ovaries. In contrast to the male sex glands, they do not fall in the development process down, and are in the lower part of the abdominal cavity.
Only if the testes and ovaries determine the development of the body of the male or female type?
No. They, in turn, regulated by hormones of the brain, called the hypothalamus and the pituitary gland.