Oo genesis Flashcards
What is oogenesis
formation of the female gamete
What does oogenesis start from
Undifferentiated primordial germ cell
How many copies of chromosomes do primordial germ cells have?
2 copies (diploid)
What are diploid cells
2 homologs of each chromosome, one from each parent
What must happen prior to fertilization for the diploid cell to be produced
number of chromosomes must be reduced, haploid cells must be made
What happens during mitosis
two identical cells are produced
What are the 5 stages of prophase 1
Leptotene zygotene pachytene diplotene diakinesis
What happens during Leptotene
chromosomes appear as thin threads
What happens during zygotene
Condensation of threads
Synapsis directed by the synaptonemal complex
What happens during pachytene
genetic rcombination
What hapens during diplotene
Homologs start to separate
What happens during diakinesis
centromers move away from each other
What happens during metaphase 1
homologs align equidistant to each other
What happpens during anaphase 1
Homologs are separated
What happens during telophase 1
two daughter cells are formed
Each daughter cell contains one copy fo the homologous chromosomes
How do oogoni multiply
Mitosis
When is meiosis arrested
Late diplotene stage (dictyate)
When does meiosis resume
until activation of the oocyte in response to ovulatory gonadotropic stimulus
What is a primoridal follicle
oocyte enclosed by single layer of pregranulosa cells
When is the 2nd meiotic division arrested
metaphase 2
when does the 2nd meiotic division resume
fertilization
What is folliculogenesis
formation of an antral follicle starting from a primordial follicle
what is a follicle
oocyte surrounded by somatic cells
Do primary and secondary follicles need gonadotropins
no
What does development beyond secondary follicles require
gonadotropins
What does FSH do
stimulate follicular growth
what does LH do
maturation of oocyte
triggers ovulation
What is the two cell two gonadotropin hypothesis
LH: Theca cell turns cholesterol to androgen
FSH: Granulosa cell, turns androgen into estrogen
What is the only positive feedback loop
Estrogen on the hypothalamus/GnRH once it reaches threshold
What happens when estrogen reaches threshold
Burst of GnRH
Surge of LH
follicular maturation and ovulation
what does the LH surge do to meiosis
causes it to resume (first polar body extruded)
what do the theca cells do after the LH surge
produce low levels of progesterone
What happens to progesterone levels during CL formation
slowly increase
What is progesterone required for
maintenance of pregnancy
What causes the CL to regress in large animals
PGF2alpha
What does the CL become after its destruction
corpus albicans
