Associated terms:
Down load as PDF
Concerning this page
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 https://datingrating.net/mylol-review and Their ducts that are accessory
Main intimate figures consist of the vagina, womb, and ov
1 The Gonads
The paired gonadal primordia arise through the intermediate mesoderm associated with embryo that is mammalian a vaginal ridge on either region of the midline in close relationship because of the transitory mesonephric renal regarding the embryo. Many derivatives associated with mesonephric renal as well as its duct system are retained because functional portions for the adult reproductive system, even though majority of the mesonephric renal degenerates. A primordium that is gonadal of a external cortex produced from peritoneum plus an internal medulla ( Figures 10-1 and 10-2 ). Germ cells don’t arise inside the gonadal primordium itself but migrate from their web site of beginning within the yolk sac endoderm to either cortex (female) or medulla (male) based upon the genetic intercourse ( Figure 10-2 ). The essential pattern of germ cellular migration is evolutionarily conserved from 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 vaginal ridge mesoderm, and (2) a host of chemical signals associated with alignment associated with the germ cells in the gonad and coalescence for the gonad that is developing. A few of the genes involved with managing germ that is primordial differentiation, migration, and meiosis are placed in dining Table 10-2.
FIGURE 10-1. Undifferentiated gonad.
Part 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 to the mesoderm for the gonad that is bipotential. The cortical tissue (orange) degenerates and the medullary tissue develops into the testis cords, which give rise to the seminiferous tubules including the Sertoli cells in the male. Mesonephric tubules produce the intratesticular ducts for instance the testis that is rete the efferent ducts and vas deferens. Into the feminine, the medullary cords degenerate, as well as the cortical cords (orange) bring about an ovary. Some mesonephric elements stay into the feminine too. The vasa deferentia are retained in amphibians but sooner or later they degenerate in reptiles, wild birds, and animals 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
| Gene | Name | Role |
|---|---|---|
| bmp 2/4/8 | bone tissue morphogenic protein | Induction 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 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 mobile 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. Differentiation associated with the sex that is primary into seminiferous cords and regression associated with cortex end in a testis. Each testis is made of seminiferous tubules based on the sex that is primary. The germ cells migrate into the tubules that are seminiferous bring about spermatogonia, and finally create semen. The Sertoli or cells that are sustentacular sperm development. Steroidogenic interstitial cells or Leydig cells can be found between your seminiferous tubules. These interstitial cells arise from medullary muscle surrounding the sex that is primary and turn resources of androgens.
In females, the principal sex cords degenerate, and additional sex cords differentiate through the cortical area. These additional intercourse cords end up being the definitive ovary. The germ cells give rise to oogonia, which soon enter meiosis to form primary oocytes in the ovary. The ovaries have follicles that comprise of 1 or even more levels of follicular cells surrounding an oocyte that is primary.
2 Accessory Ducts
A network of tubules, known as the rete testis, that do not contain seminiferous elements in males, the central portion of each differentiating testis forms. The testis that is rete a connection amongst the seminiferous tubules and a surviving percentage of the ancient mesonephric renal duct called the wolffian duct, which, intoxicated by testosterone, differentiates to the vas deferens and conducts semen through the testis into the urethra. All the mesonephric renal in animals degenerates, apart from a number of the anterior mesonephric renal tubules (see Box 10A ). This tissue together with a portion of the wolffian duct forms two glandular structures, the epididymis and the seminal vesicle ( Figures 10-2 and 10-3 ) in the presence of testosterone.