REPRO - Menstrual Cycle and Physiology Flashcards
(99 cards)
Primordial Germ Cells (PGCs) undergo many cycles of mitosis, and migrate to the genital ridge. In females they enter…
ovaries to become oogonia which are diploid egg precursors
Oogonia proliferate by mitosis then..enter meiosis and arrest..
at anaphase (meiosis I) as primary oocytes
At birth what happens to the number of primary oocytes? Why?
Massive decrease as they undergo apoptosis as errors are discarded.
Where are primary oocytes packed
the cx of ovary (outer layer)
In the foetal ovary, what are the surrounding cells that condense around the oocyte and differentiate?
These secrete what? All together this is the..
Granulosa cells, secrete an acellular layer, the basal lamina
-Together structure is the “primordial follicle”
How do follicles grow initially in follicullogenesis in puberty?
follicles grow by multiplication of granulosa cells and synthesising protein, lays down the protective Zona Pellucida layer
Once the cohort start growing in folliculogenesis, what is the second layer of cells that differentiate around the basal lamina?
The theca cells
FSH drives most of folliculogenesis. But early growth is.. in this at puberty..
FSH independent..at puberty cohort of early follicles leave the resting pool and grow continously = follicle initiation
How do the antrum (follicullar fluid filed spaces) form?
-follicle increases rapidly in diametre and granulosa cells divisions increase so gaps form in the GC’s layers (becomes fluid filled)
What are follicles with an antrum (antral follicles) AKA?
Secondary follicles
Which layer is higher vascularised and brings the circulatory influences to allow growth of the follicle?
Theca cell layer
What are the contents of follicular follicle in the antrum?
- exudate of plasma
- secretatory products of oocytes and GCs
Are pre-antral or secondary follicles visible on US next to dominant follicle?
Secondary (although pre-antral is always there, just cant see)
After follicle initiation how are some recruited?
those that can respond to FSH reach right size for recruitment into menstrual cycle (MC) when FSH is at peak
What happens to those not recruited for MC?
They are growing at a different rate/stage so die.
How many cycles does it take for a follicle to go from resting stage to ovulation?
3 cycles
In the dominant follicle the steroids produced –> “ 2 cell, 2 Gonadotrophin Theory” which means..
- LH stimulates theca cells to make androgens and progesterone
- FSH stimulates granulosa cells to make oestrogens from androgens
LH receptors are only on..
Except will appear on… just before… to enable them to make…
Theca cells
appear on…GCs just before Ovulation. to enable them to make…Progesterone
FSH receptors are only on
Granulosa cells
What effect does oestrogen have on granulosa cells and on follicles?
Multiplication and more follicle growth
What happens to the meiosis just before ovulation?
They finiish meiosis I and arrest again in metaphase II until fertilisation/death
Menstrual cycle is about 28days, when is day one?
What are the phases?
Day 1 = 1st day of bleeding
-follicullar phase and luteal phase
What happens in the follicular phase of MC? Hormone?
- growth of recruited early antral follicles
- one selected to be the dominant follicle
- oestrogen
What happens in the Luteal phase of MC? Hormone?
corpus luteum remnant of dominant follicle secretes progesterone, if no fertilisation this dies after exactly 14 days