oogenesis Flashcards
female germ cells proliferate by mitosis in the ovaries to form a large no of what?
oogonia
oogonia is diploid or haploid?
diploid, containing two x chromosomes, and will become haploid mature oocytes via process of oogenesis
what is the adult ovary made up of?
connective tissue that supports a large no of follicles
blood vessels and nerves are concentrated within the central medulla whereas follicles are found in the outer cortex in varying stages of development
meiosis I begins at what week of embryonic development
week 12
the cell at this stage is known as the primary oocyte and is surrounded by a thin layer of squamous epithelial cells
in its very early stages of development what is the primary oocyte in its thin layer of epithelial cells known as?
primordial follicle
the primary oocyte at week 12 is developmentally arrested in what phase of meiosis I?
prophase
this pause in development can continue for 45 years or more
no of primordial follicles inc during foetal period but many degenrate. leaving around 400,000 follicles available at puberty
after birth do any new oocytes form?
no
with the onset of puberty the primary oocyte becomes large and follicular cells thicken and becomes cuboidal. what is follicle now known as?
primary follicle
the oocyte and granulosa (follicle) cells produce a layer of glyoproteins on the surface of the oocyte called?
zona pellucida
when the follicle forms more than one layer of granulosa cells it is called a ?
secondary follicle
what is the name given to the cavity formed between the granulosa cells?
antrum
-> follicle is now called cumulus oophorus
connective tissue cells of the ovary around the follicle respond by differentiating and forming what two layers?
theca interna
theca externa
-> at this stage follicle is now a graafian follicle
theca interna role?
hormonal role
theca externa role?
supportive role
thecal and granulosa cells of developing follicles produce what hormone that causes what process to occur in the uterus?
oestrogen
thickening of the endometrial lining of the uterus and other preparations for receiving a fertilised oocyte
(occurs day 5 - 14 of the menstrual cycle)
the primary oocyte of the graafian follicle responds to surges in FSH and LH produced by pituitary gland on days 13-14 of the menstrual cycle resuming what process?
meoiosis I and continuing its stalled cell division.
when the primary oocyte divides it forms one large cell and one smaller remnant of the division known as?
polar body
at the end of meiosis I the oocyte has become?
secondary oocyte
what are polar bodies?
non-functional cells. receive v little of the available cytoplasm and degenrate soon after division.
how many polar bodies are formed in meiosis I and meiosis II?
1
2 in meiosis II
Meiosis II is halted in what phase of the cycle?
metaphase II
-> this will only continue if the oocyte is fertilised.
with ovulation of the secondary oocyte, what structure is left behind?
follicle remains within the ovary and becomes the corpus luteum.
in repsonse to LH the corpus luteum produces what hormones?
progesterone and oestrogen to thicken endometrium and develop its vasc, form glands in prep for implnatation
if fertilisation does not occur, corpus luteum degenerates 14 days later and becomes a scar tissue remnant of itself called?
corpus albicans
when is the endometrium shed?
when corpus luteum degenerates and hormone production ceases