L04: Ovarian Function

Question 1

Describe formation of the ovaries week 7 onwards

Answer 1

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

Question 2

What determines th formation of female gonads?

Answer 2

Lack of testosterone - hormones not needed for ovary development in utero, development dependent on normal germ cell production

Question 3

What can occur if there is a lack of germ cells/abnormal germ cells in females

Answer 3

Ovarian dysgenesis e.g. in Turners

Question 4

What is the role of post pubertal ovaries?

Answer 4

Formation of oocytes

Formation of hormones (mainly oestrogen)

Question 5

Is the ovary heterogenous?

Answer 5

No - due to different maturation stages of follicles

Question 6

Describe oogenesis

Answer 6

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

Question 7

What are the differences between male & female development?

Answer 7

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

Question 8

Describe folliculogenesis

Answer 8

AT PUBERTY
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

Question 9

Where are the ovarian hormones formed?

Answer 9

Prior to ovulation, follicles produce oestrogen

After ovulation, corpus luteum produced progesterone

Question 10

How is oestrogen produced in females?

Answer 10

Theca cells produce testosterone which diffuses to granulosa cells and is converted to oestrogen by aromatase

Question 11

What does FSH + LH act in in ovary?

Answer 11

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

Question 12

What produces the corpus luteum?

Answer 12

Remains of theca + granulosa cells after ovulation

Question 13

What is the role of oestrogen in females?

Answer 13

Growth of body & sex organs at puberty
Development of secondary sexual characteristics
Prepares endometrium for pregnancy
Thins cervical mucosa

Question 14

What is the role of progesterone in females?

Answer 14

Maintains endometrium + makes it secretory

Stimulates lactation