Future Directions and Challenges – Male Gametogenesis – Organization of the Testis – Supporting Cells – Leydig Cells – Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation AND Processes in spermatogenesis and. GAMETOGENESIS: OVOGENESIS Y ESPERMATOGENESIS Y ENFERMEDADES ASOCIADAS GAMETOGENESIS La Gametogenia.
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Oogenesis is initiated in the embryonic stage.
In mammalsthe first part of oogenesis starts in the germinal epitheliumwhich gives rise to the development of ovarian folliclesthe functional unit of the ovary.
Oogenesis consists of several sub-processes: Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oocyte meiosis, important to all animal life cycles yet unlike all other instances of animal cell division, occurs completely without the aid of spindle -coordinating centrosomes. The creation of oogonia traditionally doesn’t belong to oogenesis proper, but, instead, to the common process of gametogenesiswhich, in the female human, begins with the processes of folliculogenesisoocytogenesis, and ootidogenesis.
Oogenesis starts with the process of developing primary oocytes, which occurs via the transformation of oogonia into primary oocytesa process called oocytogenesis.
It is commonly believed that, when oocytogenesis is complete, no additional primary oocytes are created, in contrast to the male process of spermatogenesis, where gametocytes are continuously created. Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth. In contrast, DNA clock measurements do not indicate ongoing oogenesis during human females’ lifetimes.
The succeeding phase of ootidogenesis occurs when the primary oocyte develops into an ootid. This is achieved by the process of meiosis. In fact, a primary oocyte is, by its biological definition, a cell whose primary function is to divide by the process of meiosis. However, although this process begins at prenatal age, it stops at prophase I. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, called the dictyate. After menarchethese cells then continue to develop, although only a few do so every menstrual cycle.
Meiosis I of ootidogenesis begins during embryonic development, but halts in the diplotene stage of prophase I until puberty. The mouse oocyte in the dictyate prolonged diplotene stage actively repairs DNA damage, whereas DNA repair is not detectable in the pre-dictyate leptotenezygotene and pachytene stages of meiosis. As a result of meiosis I, the primary oocyte has now developed into the secondary oocyte and the first polar body. Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II.
4. Gametogenesis: Oogenesis
However, this process is also halted at the metaphase II stage until fertilizationif such should ever occur. If the egg is not fertilized, it is disintegrated and released menstruation and the secondary oocyte does not complete meiosis II and doesn’t become an ovum.
When meiosis II has completed, an ootid and another polar body have now been created. Synchronously with ootidogenesis, the ovarian follicle surrounding the ootid has developed from a primordial follicle to a preovulatory one.
Both polar bodies disintegrate at the end of Meiosis II, leaving only the ootid, which then eventually undergoes maturation into a mature ovum. The function of forming polar bodies is to discard the extra haploid sets of chromosomes that have resulted as a consequence of meiosis.
In vitro maturation IVM is the technique of letting ovarian follicles mature in vitro.
It can potentially be performed before an IVF. In such cases, ovarian hyperstimulation isn’t essential. Rather, oocytes can mature outside the body prior to IVF. Hence, no or at least a lower dose of gonadotropins have to be injected in the body.
Some algae and the oomycetes produce eggs in oogonia. In the brown alga Fucusall four egg cells survive oogenesis, which is an exception to the rule that generally only one product of female meiosis survives to maturity. Gametigenesis plantsoogenesis occurs inside the female gametophyte via mitosis. In many plants such as bryophytesfernsand gymnospermsegg cells are formed in archegonia. In flowering plantsthe female gametophyte has been reduced to an eight-celled embryo sac within the ovule inside the ovary of the flower.
Oogenesis occurs within the embryo sac and leads to the formation of a single egg cell per ovule. In ascaristhe oocyte does not gametogemesis begin meiosis until the sperm touches it, in contrast to mammals, where meiosis is completed in the estrus cycle.
From Wikipedia, the free encyclopedia. Evolution of sexual reproduction.
What is early ovarian ageing? Proc R Soc B. Basic science of reproductive medicine. Further comments in BBC news article: Germinal epithelium Tunica albuginea cortex Gametogenedis oophorus Stroma Medulla.
Isthmus Ampulla Infundibulum Fimbria Ostium. Ovarian ligament Suspensory ligament. Gartner’s duct Epoophoron Vesicular appendages of epoophoron Paroophoron. Endometrium epithelium Myometrium Perimetrium Parametrium.
Oogenesis – Wikipedia
Round ligament Broad ligament Cardinal ligament Uterosacral ligament Pubocervical ligament. Fossa of vestibule of vagina Vaginal fornix Ovogejesis Vaginal rugae Support structures Vaginal epithelium.
Crus of clitoris Corpus cavernosum Clitoral glans Hood. G-spot Urethral sponge Perineal sponge. Human physiology of sexual reproduction.
Menarche Menstruation Follicular phase Ovulation Luteal phase. Spermatogenesis spermatogonium spermatocyte spermatid sperm Oogenesis oogonium oocyte ootid ovum Germ cell gonocyte gamete.
Ovum Oviposition Oviparity Ovoviviparity Vivipary. Hypothalamic—pituitary—gonadal axis Hypothalamic—pituitary—prolactin axis Andrology Hormone. Thelarche Development Lactation Breastfeeding. Sex portal Biology portal. Retrieved from ” https: Developmental biology Genetics Human female endocrine system Meiosis. All articles with unsourced statements Articles with unsourced statements from May Views Read Edit View history.
Adnexa Ovaries Follicles corpus hemorrhagicum luteum albicans Theca of follicle externa interna Follicular antrum Follicular fluid Corona radiata Zona pellucida Membrana granulosa Perivitelline ovogensis.