gonaderna

Gonaderna, or the gonads, are the primary reproductive organs in many animals, including humans. They produce gametes—sperm in males and oocytes in females—and secrete sex hormones that influence sexual development, reproduction, and secondary sexual characteristics.

In humans, the gonads develop from the bipotential gonadal ridge during early embryogenesis. The presence of the SRY gene on the Y chromosome directs testicular development; in its absence, ovaries form. The testes are located in the scrotum and the ovaries in the pelvic cavity, each surrounded by supportive tissue and ligaments that keep them in place.

Gametogenesis refers to the formation of mature gametes. Spermatogenesis occurs in the testes after puberty, producing sperm through meiosis and cellular differentiation. Oogenesis begins before birth in females, with oocytes arrested at prophase I and resumes cyclically after puberty, resulting in a monthly release of oocytes and, typically, one mature ovum per cycle.

Gonadal hormones regulate development and function. In males, testosterone produced by Leydig cells drives male characteristics and spermatogenesis. In females, estrogens and progesterone from ovarian follicles and corpora lutea regulate the menstrual cycle and reproductive readiness. Gonadotropins from the pituitary gland, namely luteinizing hormone (LH) and follicle-stimulating hormone (FSH), coordinate development and gametogenesis under regulation by GnRH from the hypothalamus.

Variations exist across species, including hermaphroditism and species with different patterns of sex chromosome systems. In humans, gonadal disorders can involve dysgenesis or impaired hormone production, and aging can lead to decreased gonadal function.