Lecture 05: Female Gonad - Oogenesis (Kelleman) Flashcards
largest cell in the body
female gamete
oogenesis =
formation of the female gamete
spermatogenesis =
formation of the male gamete
When does oogenesis arrest? ** When does it resume development?
Prophase I (late diplotene/dictyate stage). Resumes development either by LH surge during ovulation, or by hormonal control pre-ovulation. In the latter case, it will only reach metaphase II. Ultimately, fertilization must occur for oocyte to fully develop.
primordial germ cells migrate from where to where?
from yolk sac to genital ridge
PGCs undergo mitosis or meisosis?
mitosis
oogonia and how do they replicate?
PGCs that have reached genital ridge and lost their motility. 2n. Replicate by mitosis
primary oocyte
formed by meiosis of oogonia. Still 2n diploid!
folliculogenesis
formation of an antral follicle starting from a primordial follicle
follicle =
oocyte surrounded by somatic cells
difference between tertiary and Graafian follicle?
antrum has formed in Graafian follicle
What does LH control? ***
ovulation (final follicular maturation)
primordial follicle and when is it formed? **
Primary oocyte surrounded by a single layer of pregranulosa cells. Forms during fetal life
Primary follicle
oocyte surrounded by a single layer of cuboidal granulosa cells
when does zona pellucida start forming?
in primary follicle
at what stage does follicle develop independent blood supply and become sensitive to hormone regulation?
secondary follicle (early development is independent of gonadotropic hormonal support)
at what stage does theca differentiate into theca interna and externa?
tertiary follicle
FSH fx
stimulates follicular growth
LH fx
maturation of the oocyte, triggers ovulation
location of FSH receptors
granulosa cells
location of LH receptors
thecal cells, (+granulosa cells in late stages)
Two-cell-two-gonadotropin-hypothesis
thecal cells produce androgens via LH, which then diffuse into granulosa cells where they are converted to estrogens via FSH
1st meiotic division
separates homologous chromosomes. Results in two haploid daughter cells which each contain only 1 copy of each homolog
2nd meiotic division
separates the two sister chromatids from eachother. Results in 4 haploid cells
synthesis phase of 1st meiotic division
Occurs before prophase I. Results in two-chromatid chromosomes (2n, 4C), in a diploid stem cell
5 subphases of prophase I
1) leptotene
2) zygotene
3) pachytene
4) diplotene
5) diakinesis
leptotene phase of prophase I
1st subphase. condensation of chromatin into thin threads
zygotene phase of prophase I
2nd subphase. Homologous chromosomes pair (known as synapsis)
pachytene phase of prophase I
3rd subphase. Crossing over occurs
diplotene phase of prophase I
4th subphase. Homologs separate. Where first meiotic arrest occurs
diakinesis phase of prophase I
5th subphase. centromeres move away from each other and nuclear membrane breaks down. Occurs AFTER meiosis is resumed, after LH surge preceding ovulation
Metaphase I
homologs align on metaphase plate (2n, 4C)
Anaphase I
homologs are separated from eachother (2n, 4C)
Telophase I
two unequal daghter cells are formed, each containing 1 copy of homologous chromosome pair. (1n, 2C)
When does SECOND arrest of oogenesis occur? When does it resume?
Metaphase II. Resumes after fertilization to complete second meiotic division
2nd meiotic division is similar to ______ but results in what kind of cells?
mitosis; forms polar body and pronucleate oocyte (what joins with sperm) which are both 1n, 1C
when does oogonia become primary oocyte?
when it independently starts meiosis
What happens to oocyte after 1st meiotic block/arrest?
oocyte dramatically increases in size, zona pellucida forms, follicle housing oocyte develops
cortical granules fx
surround oocyte to prevent polyspermy
when does 1st meiotic division end?
when 1st polar body is extruded
when does 2nd meiotic division end?
upon fertilization and extrusion of 2nd polar body
how many chromosomes/chromatids in primary oocyte? secondary oocyte? pronucleated egg?
primary: 2n,4C
secondary: 1n,2C
pronucleated egg: 1n,1C (is formed after fertilization; what joins with sperm)
sidenote: females, like males, have the capacity to renew their germ cell pool during adult life
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