In amphibians the germ cells arise in the vegetal pole region whereas in mammals the cells arise in the extraembryonic yolk sac mesoderm and then must . The process of Gametogenesis is stimulated by the FSH or Follicle . eggs of shark, bony fish, Reptiles, birds, prototherian, concentrated mainly in vegetal pole . marginal zone, transitional area between animal and vegetal hemispheres. maturation, process of gaining fully differentiated form. maturation promoting factor.

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The primary germ cells multiply by repeated mitotic division. During cleavage stage, individual blastomeres veggetal be clearly detected when viewed under the microscope. Reinitiation of meiosis in the fully-grown oocyte is the first sign of oocyte maturation, which involves condensation of interphase chromatin, breakdown of nuclear membrane germinal vesicle breakdown: Difference between Spermatogenesis and Oogenesis Embryology.

These include sperm capacitation, sperm binding and penetration of the ZP, traversing the perivitelline space PVSbinding and fusion with oolemma, activation of the oocytes and decondensation of the sperm head to form the Male PN MPN. The walls of the seminiferous tubules contain the differentiating sex cells arranged in a stratified layer, 5 to 8 cells deep.

Useful Notes on Gametogenesis (Spermatogenesis and Oogenesis)

During this growth phase there is a major increase in ooplasmic organelles. A profile of fertilization in mammals. The primary oocyte undergoes two successive divisions by meiosis. Thus, in goat, where the chromosome number of somatic cells is 60, each sperm and each oocyte has only 30 chromosomes. During postnatal life, starting from puberty, ovarian follicles continue to grow, mature and either ovulate or regress.

It was suggested that although a single rise is sufficient to produce activation, oscillations might gametobenesis required for additional developmental events Ozil, After continuation of meiosis, the oogenesis process until completion is very fast.

Before and at the time of LH surge, the oocyte is surrounded by a compact CCs investment. Germ Cells and Fertilization, Austin, C.


The outermost layers contain spermatogonia, which have increased in number by spemtocytogenesis. The acrosome is membrane-bound gametofenesis contains lytic agents such as proteases, sulphatases and glycosidases.

Sertoli cells also have a role in supporting the developing spermatozoa. If you do not agree to the foregoing terms and conditions, you should not enter this site. Stages of spermatogenesis the generation of sperm Heterologous cell contacts and metabolic coupling in bovine cumulus oocyte complexes.


The goat embryo stays in the oviduct for 48 to 72 h from the time of ovulation Moore, Meiotic competence of in vitro grown goat oocytes. Through a series of mitotic division of GCs, unilaminar primary follicles are converted to multilaminar secondary follicles, followed by the antral or tertiary follicles Miyano and Hirao, Therefore, the current study is intended to review gametogenesis, sperm oocyte interaction, fertilization and early embryogenetic process in mammals with special reference to goat.

The spermatozoa must reside a minimum period in the female reproductive tract before gaining the ability to fertilize oocytes Austin, ; Chang, After losing its acrosomal content the spermatozoon retains only the inner acrosomal membrane that makes direct contact with the ZP during penetration.

Ooplasmic maturation is required to acquire to the conditions to block polyspermy in case of fertilization, to decondense penetrated spermatozoon and to form pronucleus PN. In cattle, oocytes originating from follicles larger than 6 mm in diameter yield a significantly higher percentage of blastocyst than the smaller follicles Lonergan et al.

Cleavage divisions are always mitotic and each blastomere receives full assortment of chromosomes. Although the blastomeres undergo mitosis like adult somatic cells and their number increases, however, unlike somatic cells they do not retain the size of the parent cell.

Oogenesis in mammals includes seven steps: On the other hand, the ZP of the oocyte is made up of protein and carbohydrates in the form of glycoprotein units that are probably stabilized by disulphide bonds.

Useful Notes on Gametogenesis (Spermatogenesis and Oogenesis)

The gametes initially colonize in the primitive gonadal ridge at the early stage of pregnancy by migration through the developing mesentery of the embryo, where germ cells associate with somatic cells; it continues gmetogenesis their multiplication, growth and maturation. Why might the spermatogenesis process require the developing sperm cells gametoggenesis be in a syncytium? The walls of mature preovulatory follicles consist of membrana granulosa mural granulosatheca interna and theca externa.

The ooplasmic opacity in different animals and human has been presented in Table 1.

Meiosis occurs in the descendants of these cells. Origin of the germ cells. This is supported by in vitro experiments in Xenopus laevisan amphibian species Brun,mouse Vegettal and Yanagimachi, and human Palermo et al.


Cells cannot live without the X chromosome they would be missing thousands of genes for basic housekeeping cell functions such as the gene for glucose 6 phoshphate dehydrogenase.

Formation of mammalian oocytes and their growth, differentiation and maturation within ovarian follicles. The CCs in close contact with the oocyte are known as corona radiata. In vitro growth of oocytes from domestic species.

Although, it is not clear whether the AR is initiated whilst the sperm is interacting with the cumulus mass, however, it is speculated that the reaction may be started in the CCs as a major component of the cumulus matrix is hyaluronic acid and the acrosome contains hyaluronidase. Ultimately, the nuclear and ooplasmic maturity of the oocyte influences the success of fertilization gameyogenesis embryo development. To get success in any in vitro studies in any species of animals it crucial to know the normal fertilization process that occurs in vivo.

In goat, the blastocoel appears at h post-fertilization Sakkas et al. The plane of second division is also vertical and passes through the main axis but at a right angle to the initial plane of cleavage, resulting in 4 blastomeres.

The chronology of embryo development from 2-cell stage to blastocyst hatching in different species of farm animals including goat, rabbit, mouse and human has been presented in Table 3. The attachment of the sperm head to the ZP inevitably alters the permeability of the sperm plasma membrane, causing a transient change in the concentration of several intracellular ions Tulsiani et al. DNA replication and cell divisions occur without an increase in cell mass to attain a ratio similar to somatic cells.

Direct and continuous assessment by veyetal of their position in a morphogen gradient. Protamines are replaced by the histones generated by the oocyte.

Veegtal mammalian species, activation of spermatozoa follows several physiological and structural changes upon exposure to environmental signals in the female reproductive tract before they interact with the oocytes towards a successful fertilization. Meiosis occurs in the adluminal compartment of the Sertoli cell and results in the formation of primary spermatocytes.