Write a Brief Overview on Development of Testis and Ovary
The development of the testis and ovary, known as gonadal differentiation, occurs during embryogenesis and determines the sexual characteristics of the individual. Initially, embryos possess undifferentiated gonads capable of forming either testes or ovaries.
1. Indifferent Stage
- In early embryonic development (around 5th to 6th week), the gonads are indistinguishable in both sexes.
- The genital ridge forms adjacent to the mesonephros and is colonized by primordial germ cells.
2. Testis Development
- Triggered by the presence of the SRY gene (Sex-determining Region Y) on the Y chromosome.
- SRY gene induces formation of Sertoli cells and Leydig cells.
- Sertoli cells promote development of testis cords and produce Anti-Müllerian Hormone (AMH), causing regression of Müllerian ducts.
- Leydig cells produce testosterone, stimulating development of male internal and external genitalia.
3. Ovary Development
- Occurs in absence of the SRY gene.
- Primordial germ cells proliferate and differentiate into oogonia.
- Medullary cords degenerate while cortical cords form follicles around the oogonia.
- Ovaries develop and support female reproductive structures.
In conclusion, the differentiation of the testis or ovary from the primitive gonad depends on genetic signals, particularly the presence or absence of the SRY gene. This differentiation is critical for determining the future sexual characteristics and reproductive functions of the individual.