Flashcards in L04: Ovarian Function Deck (14):
Describe formation of the ovaries week 7 onwards
Same influx of cells as males:
- Sex cord cells cluster around PGCs forming primitive follicles, sex cord cells become granulomas cells
- PGCs migrate + become oogonia
- mesonephric cells form theca cells + vasculature
What determines th formation of female gonads?
Lack of testosterone - hormones not needed for ovary development in utero, development dependent on normal germ cell production
What can occur if there is a lack of germ cells/abnormal germ cells in females
Ovarian dysgenesis e.g. in Turners
What is the role of post pubertal ovaries?
Formation of oocytes
Formation of hormones (mainly oestrogen)
Is the ovary heterogenous?
No - due to different maturation stages of follicles
PGCs —> oogonia after association w sex cord cells in utero
Oogonia —> primary oocyte (mitosis)
Meiosis of primary oocyte starts in utero but is arrested at prophase 1 + completed just before ovulation to form secondary oocyte
Secondary oocyte starts 2nd meiotic division but is arrested at metaphase II until fertilisation
Formation of tertiary oocyte after ovulation as meiosis 2 is occurring
What are the differences between male & female development?
1. Timing of entry to meiosis - in utero in females, after puberty in males
2. Oogenesis is not continuous
3. Oocytes undergo atresia to select best eggs
4. Female meiotic divisions are asymmetrical (polar bodies)
5. Females have finite no of oocytes
6. Oogenesis is cyclic
Starts with the development of primary follicle from primordial follicle in utero
- oocyte gets bigger, produces proteins for maturation, granulomas cells become cuboidal, theca cells visible (independent of LH/FSH)
Formation of ZP glycoprotein coat allowing granulosa cell processes to maintain contact w oocyte
Formation of 5-15 secondary follicles - dependent on LH + FSH, granulosa cell’s proliferate + theca interna + externa form
Formation of tertiary follicle dependent on FSH selecting 1, primary oocyte completes meosis I to form secondary oocyte, formation of antrum fillies w follicular fluid secreted by granulosa cells, formation of corona radiata + cumulus oophorous
Where are the ovarian hormones formed?
Prior to ovulation, follicles produce oestrogen
After ovulation, corpus luteum produced progesterone
How is oestrogen produced in females?
Theca cells produce testosterone which diffuses to granulosa cells and is converted to oestrogen by aromatase
What does FSH + LH act in in ovary?
FSH acts on FSH receptor on granulosa cells to stimulate follicle development
LH acts on LHCG receptors on theca cells to induce follicle maturation, ovulation + development of corpus luteum
What produces the corpus luteum?
Remains of theca + granulosa cells after ovulation
What is the role of oestrogen in females?
Growth of body & sex organs at puberty
Development of secondary sexual characteristics
Prepares endometrium for pregnancy
Thins cervical mucosa