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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 intimate figures consist of the vagina, womb, and ov
1 The Gonads
The paired gonadal primordia arise through the intermediate mesoderm for the mammalian embryo as a vaginal ridge on either part of this midline in close relationship aided by the transitory mesonephric renal associated with embryo. Many derivatives regarding the mesonephric renal and its particular duct system are retained as functional portions associated with adult reproductive system, even though almost all the mesonephric renal degenerates. A primordium that is gonadal of an exterior cortex produced from peritoneum and an internal medulla ( Figures 10-1 and 10-2 ). Germ cells don’t arise in the gonadal primordium itself but migrate from their site of beginning within the yolk sac endoderm to either cortex (female) or medulla (male) based upon the sex that is genetic Figure 10-2 ). The fundamental pattern of germ mobile migration is evolutionarily conserved from 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 for the germs cells to your genital ridge mesoderm, and (2) a russian bride host of chemical signals involved with positioning regarding the germ cells inside the gonad and coalescence associated with the developing gonad. A number of the genes tangled up in managing primordial germ mobile differentiation, migration, and meiosis are placed in dining Table 10-2.
FIGURE 10-1. Undifferentiated gonad.
Portion 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, Nyc, 1978, pp. 47–81. )
FIGURE 10-2. Growth of testis and ovary in humans.
Primordial germ cells migrate from the hindgut in to the mesoderm of this gonad that is bipotential. When you look at the male, the cortical muscle (orange) degenerates and also the medullary muscle develops to the testis cords, which produce the seminiferous tubules including the Sertoli cells. Mesonephric tubules bring about the intratesticular ducts including the rete testis and the efferent ducts and vas deferens. When you look at the feminine, the medullary cords degenerate, in addition to cortical cords (orange) bring about an ovary. Some mesonephric elements stay when you look at the feminine too. The vasa deferentia are retained in amphibians but sooner or later they degenerate in reptiles, wild wild birds, and mammals where 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 protein that is morphogenic and competence of PGCs|
|prdm1 and prdm14/blimp1 (mouse)||PR domain zinc finger protein 1||necessary for PGC specification|
|pou5f1||POU domain course 5, transcription factor 1||PGC marker and specification|
|vasa; ddx4||DEAD box category 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 mobile growth element receptor (SCFR); proto-oncogene c-kit||Migration, entry into mesoderm|
|dazl||Deleted in azoospermia-like||Meiosis competency|
Initially, the medullary component in males and females differentiates into primary intercourse cords. Continue reading “Primary Sexual Faculties”