OOgenesis Flashcards
How does the egg cell form?
Primordial germ cell undergoes mitosis and forms oogonium. Oogonium continues mitosis to form primary oocyte. Primary oocyte enters meiosis I to form haploid secondary oocyte and cytokinesis during this process forms a polar body. Polar body will die. In Meiosis II, diploid secondary oocyte forms the ovum along another polar body which will die.
What happens to eggs during development?
From primordial germ cell, they undergo mitosis and arrest in Meiosis I as a primary oocyte while in utero. It does not undergo oogenesis until puberty with the start of the menstrual cycle.
How does first polar body form?
Cytokenesis of the primary oocyte during meiosis I is unequal and forms 2 structures: a haploid oocyte and a haploid polar body with small amounts of cytoplasm. Polar body may divide but will eventually undergo apoptosis.
How does the second polar body form?
Cytokenesis of the secondary oocyte during meisosi II is unequal and forms ovum and second polar body which immediately undergoes apoptosis.
What is a bivalent set of chromosomes?
Set of 2 homologous chromosomes joined together at chaisma- one being from mother, one being from father joined in meiosis I.
Difference between first and second polar body?
First polar body has bivalent set of chromosome which can continue to divide but will eventually undergo apoptosis. Second polar body has hapoid sister chromatids which will immediately undergo apoptosis.
What is folliculogenesis?
Occurs in menstruation. Ovum formed from meisois II undergoes 3 phases to form a mature follicle for fertilisation: Pre-antal phase, antral phase and pre-ovulatory phase
What is the pre-antral phase?
Primary oocyte grows while being arrested in meisois I. Follicular cells proliferate and form stratified cuboidal layer called granulosa cells surrounding it. Granulosa cells secrete glycoprotein of zona pellucida. This forms the primary follicle
What allows primary occyte to enter antral phase?
Primary follicle -> secondary follicle. Secondary follicle has more layers of granulosa cells and an outer theca. It will progresses to a tertiary follicle dependent on levels of LH and FSH in the body. If this is low, atresia occurs.
Antral phase
Fluid filled space forms between secondary oocyte granulosa cells, which develop under influence of FSH and LH to form tertiary oocye
What is the structure of a mature oocyte?
It has an outer layer of theca cells, then granulosa cells and a much larger antrum than teritary follicle. Oocyte is surrounded by cumulus oophorus and connected to granulosa cells via stalk.
Visceral layer of testis
Tunica vaginalis
Parietal layer of testis
Tunica vaginalis
What stage is the oocyte in ovulation?
Becomes a secondary oocyte.
