A gonad (from the Greek gone , 'sex', 'generation', 'seed', and aden , 'gland'), also called the sex gland or sex gland , is the ( endocrine ) sex organ in which some sex hormones and all germ cells (gametes) are formed.
The gonads are created in pairs. The development of the gonads in the embryo is initially the same in both sexes. Only the sex-determining region of Y (SRY ) located on the Y chromosome (→ genetic sex ) in mammals determines the development of the testes via the testicular-determining factor (TDF) or, in the absence of this, the development of the ovary. Part of the gonadal anlage develops into the gonadal ligaments . Due to the early differentiation, the gonads are also one of the primary sexual characteristics . Their presence accordingly determines the gonadal gender . Wrong developments can lead to the development of an ovotestis .
In female birds , the right ovary usually recedes completely during embryonic development, the female reproductive organs only develop on the left.
The function of the gonads can be divided into an exocrine and an endocrine component:
The exocrine component consists in providing the germ cells in the sexually mature individual: egg cells in women, sperm cells in men. By means of spermatogenesis, men can produce fertilizable sperm cells from puberty to old age . In women, oogenesis is already completed in the 5th month of development and it has reached its maximum of around 7 million germ cells, which now enter the protective dictyotene stage. At the onset of puberty, only about 400,000 of these female germ cells are left. Less than 500 of them take place during the reproductive phase of women to the menopause a follicle .
Switching off the gonadal function or removing the gonads is called castration in both sexes .
The diseases of the gonads include Gonadeninsuffizienzen ( hypogonadism , menopause ) and Gonadenüberfunktionen (hypergonadism, occurring in seminomas , teratomas , Chorionepitheliomen , Leydig cell tumors, feminizing or masculinizing tumors (about Arrhenoblastome ), polycystic ovary syndrome , idiopathic hirsutism and complete androgen insensitivity ).
- The gonad. In: Stephen Nussey, Saffron Whitehead: Endocrinology. Informa Healthcare, Oxford 2001, ISBN 1-85996-252-1 .
- See Ludwig Weissbecker: diseases of the gonads. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition, ibid. 1961, pp. 1025-1033.