Скачать или смотреть How testis are formed in male children

The formation of the testes in male children begins during embryonic development. Here's an overview of the process:

1. Genetic Determination (Week 7 of Development)
The sex of an embryo is determined at conception when a sperm cell carrying either an X or Y chromosome fertilizes an egg. If the embryo inherits a Y chromosome, it will typically develop male characteristics.
A specific gene on the Y chromosome called SRY (Sex-determining Region Y) triggers the formation of testes. The presence of the SRY gene leads to the development of testes, while its absence results in the formation of ovaries.
2. Formation of Gonadal Ridges (Weeks 4-6)
Early in development, around weeks 4 to 6 of pregnancy, the embryo has a pair of undifferentiated structures called gonadal ridges. These ridges have the potential to develop into either testes or ovaries.
The SRY gene begins to influence these gonadal ridges, guiding them to develop into testes.
3. Differentiation into Testes (Weeks 7-12)
Under the influence of the SRY gene, the gonadal ridges start transforming into testes around the 7th week of development.
Inside the developing testes, special cells called Sertoli cells form and help with the further differentiation process.
By week 8-9, another type of cells, Leydig cells, begin to develop, and they start producing testosterone.
4. Production of Hormones
Testosterone, produced by Leydig cells, plays a crucial role in promoting the development of male characteristics. It influences the formation of internal male reproductive organs like the vas deferens, epididymis, and seminal vesicles.
Testosterone also indirectly supports the development of external genitalia, such as the penis and scrotum.
5. Descent of the Testes (Third Trimester)
Initially, the testes are located inside the abdomen. As the fetus grows, the testes gradually descend into the scrotum through a canal called the inguinal canal. This descent typically happens during the third trimester of pregnancy (between weeks 26 and 36).
The development of testes is critical for producing sperm and male sex hormones (like testosterone) after birth and during puberty. This entire process is regulated by a complex interaction of genes and hormones during fetal development.