Lecture 05: Female Gonad - Oogenesis (Kelleman) Flashcards Preview

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Flashcards in Lecture 05: Female Gonad - Oogenesis (Kelleman) Deck (43):
1

largest cell in the body

female gamete

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oogenesis =

formation of the female gamete

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spermatogenesis =

formation of the male gamete

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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.

5

primordial germ cells migrate from where to where?

from yolk sac to genital ridge

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PGCs undergo mitosis or meisosis?

mitosis

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oogonia and how do they replicate?

PGCs that have reached genital ridge and lost their motility. 2n. Replicate by mitosis

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primary oocyte

formed by meiosis of oogonia. Still 2n diploid!

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folliculogenesis

formation of an antral follicle starting from a primordial follicle

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follicle =

oocyte surrounded by somatic cells

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difference between tertiary and Graafian follicle?

antrum has formed in Graafian follicle

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What does LH control? ***

ovulation (final follicular maturation)

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primordial follicle and when is it formed? **

Primary oocyte surrounded by a single layer of pregranulosa cells. Forms during fetal life

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Primary follicle

oocyte surrounded by a single layer of cuboidal granulosa cells

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when does zona pellucida start forming?

in primary follicle

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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)

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at what stage does theca differentiate into theca interna and externa?

tertiary follicle

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FSH fx

stimulates follicular growth

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LH fx

maturation of the oocyte, triggers ovulation

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location of FSH receptors

granulosa cells

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location of LH receptors

thecal cells, (+granulosa cells in late stages)

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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

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1st meiotic division

separates homologous chromosomes. Results in two haploid daughter cells which each contain only 1 copy of each homolog

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2nd meiotic division

separates the two sister chromatids from eachother. Results in 4 haploid cells

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synthesis phase of 1st meiotic division

Occurs before prophase I. Results in two-chromatid chromosomes (2n, 4C), in a diploid stem cell

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5 subphases of prophase I

1)leptotene
2) zygotene
3) pachytene
4) diplotene
5) diakinesis

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leptotene phase of prophase I

1st subphase. condensation of chromatin into thin threads

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zygotene phase of prophase I

2nd subphase. Homologous chromosomes pair (known as synapsis)

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pachytene phase of prophase I

3rd subphase. Crossing over occurs

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diplotene phase of prophase I

4th subphase. Homologs separate. Where first meiotic arrest occurs

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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

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Metaphase I

homologs align on metaphase plate (2n, 4C)

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Anaphase I

homologs are separated from eachother (2n, 4C)

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Telophase I

two unequal daghter cells are formed, each containing 1 copy of homologous chromosome pair. (1n, 2C)

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When does SECOND arrest of oogenesis occur? When does it resume?

Metaphase II. Resumes after fertilization to complete second meiotic division

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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

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when does oogonia become primary oocyte?

when it independently starts meiosis

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What happens to oocyte after 1st meiotic block/arrest?

oocyte dramatically increases in size, zona pellucida forms, follicle housing oocyte develops

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cortical granules fx

surround oocyte to prevent polyspermy

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when does 1st meiotic division end?

when 1st polar body is extruded

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when does 2nd meiotic division end?

upon fertilization and extrusion of 2nd polar body

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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)

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sidenote: females, like males, have the capacity to renew their germ cell pool during adult life

:)

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