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The Endocrinology of Mammalian Reproduction
David O. Norris Ph.D., James A. Carr Ph.D., in Vertebrate Endocrinology (Fifth Edition), 2013
A Embryogenesis of Gonads and Their Accessory Ducts
Main characters that are sexual the vagina, uterus, and ov
1 The Gonads
The paired gonadal primordia arise through the intermediate mesoderm of this embryo that is mammalian a vaginal ridge on either part of this midline in close relationship aided by the transitory mesonephric renal associated with the embryo. Many derivatives of this mesonephric kidney as well as its duct system are retained since functional portions regarding the adult reproductive system, even though majority of the mesonephric renal degenerates. A gonadal primordium comprises of a external cortex based on peritoneum plus a internal medulla ( Figures 10-1 and 10-2 ). Germ cells don’t arise in the gonadal primordium itself but migrate from their web web site of beginning when you look at the yolk sac russian bride endoderm to either cortex (female) or medulla (male) dependant on the sex that is genetic Figure 10-2 ). The essential pattern of germ cell migration is evolutionarily conserved from fresh good fresh good fresh fruit flies to people and needs a complex interplay between (1) guidance signals and extracellular matrix attachment proteins that assure directed migration of this germs cells into the vaginal ridge mesoderm, and (2) a host of chemical signals associated with alignment of this germ cells in the gonad and coalescence associated with developing gonad. A few of the genes taking part in managing germ that is primordial differentiation, migration, and meiosis are placed in dining dining dining Table 10-2.
FIGURE 10-1. Undifferentiated gonad.
Element of gonad from 25-mm tadpole of Rana pipiens showing cortical (c) and medullary (m) cells divided with a basal lamina (bl = cellar membrane layer). (a) total gonad (upper left); (b) enhancement; (c) further enlargement showing contact between cortical and medullary cells (arrow).
(Reprinted with authorization from Merchant-Larios, M., in “The Vertebrate Ovary” (R.E. Jones, Ed. ), Plenum, Ny, 1978, pp. 47–81. )
FIGURE 10-2. Growth of testis and ovary in humans.
Primordial germ cells migrate from the hindgut to the mesoderm associated with the gonad that is bipotential. Into the male, the cortical muscle (orange) degenerates and also the medullary muscle develops to the testis cords, which bring about the seminiferous tubules such as the Sertoli cells. Mesonephric tubules bring about the intratesticular ducts including the testis that is rete the efferent ducts and vas deferens. Into the feminine, the medullary cords degenerate, plus the cortical cords (orange) bring about an ovary. Some mesonephric elements stay within the feminine too. The vasa deferentia are retained in amphibians but sooner or later they degenerate in reptiles, wild wild birds, and animals in which the ureters develop to strain the metanephric kidneys (not present in anamniotes).
(adjusted with authorization from Paxton, M., “Endocrinology Biological and Medical Perspectives, ” William C. Brown, Dubuque, IA, 1986. )
TABLE 10-2. Some Genes Involved in Primordial Germ Cell (PGC) Induction, Specification, Migration, and Meiosis
|bmp 2/4/8||Bone morphogenic protein||Induction and competence of PGCs|
|prdm1 and prdm14/blimp1 (mouse)||PR domain zinc finger protein 1||needed for PGC specification|
|pou5f1||POU domain course 5, transcription element 1||PGC marker and specification|
|vasa; ddx4||DEAD box group of ATP-dependent RNA helicases||PGC marker and specification|
|nanos3||Nanos homolog 3||Migration, entry into mesoderm|
|dnd1||Dead end homolog 1||Migration, entry into mesoderm|
|kit||Mast/stem cellular development element receptor (SCFR); proto-oncogene c-kit||Migration, entry into mesoderm|
|dazl||Deleted in azoospermia-like||Meiosis competency|
Initially, the medullary component in men and women differentiates into primary intercourse cords.