5.0 Female Gametogenesis Flashcards Preview

MedST IB: Human Reproduction (HR) > 5.0 Female Gametogenesis > Flashcards

Flashcards in 5.0 Female Gametogenesis Deck (17)
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1

When do oocytes arrest in dictyate stage?

1st Meiotic prophase

(dictyate stage is a stage of Diplotene in prophase)

2

What are the stages of oocyte development?

Primordial follicle → preantral follicle → antral follicle → pre-ovulatory follicle → ovulation → corpus luteum

3

Features of primordial follicle:

50μm
Non-growing
In periphery of ovarian cortex
Most never progress past this stage
Few initiate each day (unknown signal)
Consist of:
1) Oocyte
2) Granulosa cells (single layer surrounding oocyte)
3) Memrana granulosa (connected to basement membrane)

4

Features of preantral follicle:

>120μm (++ RNA and protein synthesis)
Still in dictyate stage
Consists of:
1) Oocyte
2) Zona pellucida
- Layer of glycoprotein between oocyte + granulosa
- Secreted by oocyte
2) Granulosa cells
- Now grown to be several layers
- Avascular
3) Theca
- From condensation of stroma
- Blood vessels infiltrate here

5

Features of antral follicle:

No significant growth (but RNA replication and protein synthesis still going on)
Granulosa cells
Proliferate to many levels
Secrete follicular fluid → antrum
Cumulus oophros
Dense granulosa cells around oocyte
Connected to mural granulosa by stalk

6

What hormones are involved in the antral stage:

Hormones needed: LH + FSH
Hormones made: Androgens, oestrogens + inhibin

Steps:

1) LH → thecal cells → androgen secretion
2) FSH → granulosa cells → convert androgens to oestrogens
3) Granulosa cells → secrete inhibin → make thecal cells secrete more andogrens and granulosa cells convert more to oestrogen

7

Features of pre-ovulatory follicle:

High LH levels needed
High amounts of oestrogen made (+ve feedback)
Follicular fluid ↑ → antrum swells
Granulosa cells
Also develop LH receptors
LH → granulosa → PROGESTERONE
Oocyte
High LH stimulates reactivation of meiosis

8

What occurs during reactivation of meiosis?

1) Completes first cycle of meiosis:
(reactivated from prophase) → metaphase → anaphase → telophase

2) 1st meiotic division is unequal
Produces large oocyte (secondary oocyte) and first polar body (subsequently dies)

3) Seconday oocyte arrests in 2nd meiotic metaphase
Ovulated in this stage

9

What occurs in ovulation?

Rupture → outflow of follicular fluid, oocyte and cumulus cells

Residual follicle → corpus luteum

10

What hormones are needed for follicle to rupture?

LH + prostaglandins

11

What do the granulosa cells transform into (part of corpus luteum)?

Large luteal cells

12

What do the thecal cells transform into (part of corpus luteum)?

Small luteal cells

13

What do the large luteal cells secrete?

1) Progesterone
2) Oestrogen
3) Inhibin

14

What do the small luteal cells secrete?

1) Androgens

15

What hormone does the corpus luteum need to form?

LH

16

What is the life span of the corpus luteum?

14 days

17

What can prevent luteolysis?

Persisting high LH levels (pregnancy)