5.0 Female Gametogenesis

Question 1

When do oocytes arrest in dictyate stage?

Answer 1

1st Meiotic prophase<br></br><br></br>(dictyate stage is a stage of Diplotene in prophase)

Question 2

What are the stages of oocyte development?

Answer 2

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

Question 3

Features of primordial follicle:

Answer 3

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

Question 4

Features of preantral follicle:

Answer 4

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

Question 5

Features of antral follicle:

Answer 5

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

Question 6

What hormones are involved in the antral stage:

Answer 6

Hormones needed: <b>LH</b> + <b>FSH</b><br></br>Hormones made: <b>Androgens</b>, <b>oestrogens</b> + <b>inhibin</b><br></br><br></br>Steps:<br></br><br></br>1) LH → thecal cells → androgen secretion<br></br>2) FSH → granulosa cells → convert androgens to oestrogens<br></br>3) Granulosa cells → secrete inhibin → make thecal cells secrete more andogrens and granulosa cells convert more to oestrogen

Question 7

Features of pre-ovulatory follicle:

Answer 7

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

Question 8

What occurs during reactivation of meiosis?

Answer 8

<b>1) Completes first cycle of meiosis:</b><br></br>(reactivated from prophase) → metaphase → anaphase → telophase<br></br><br></br><b>2) 1st meiotic division is unequal</b><br></br>Produces large oocyte (secondary oocyte) and first polar body (subsequently dies)<br></br><br></br><b>3) Seconday oocyte arrests in 2nd meiotic metaphase</b><br></br>Ovulated in this stage

Question 9

What occurs in ovulation?

Answer 9

Rupture → outflow of follicular fluid, oocyte and cumulus cells<br></br><br></br>Residual follicle → corpus luteum

Question 10

What hormones are needed for follicle to rupture?

Answer 10

LH + prostaglandins

Question 11

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

Answer 11

Large luteal cells

Question 12

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

Answer 12

Small luteal cells

Question 13

What do the large luteal cells secrete?

Answer 13

1) Progesterone<br></br>2) Oestrogen<br></br>3) Inhibin

Question 14

What do the small luteal cells secrete?

Answer 14

1) Androgens

Question 15

What hormone does the corpus luteum need to form?

Answer 15

LH

Question 16

What is the life span of the corpus luteum?

Answer 16

14 days

Question 17

What can prevent luteolysis?

Answer 17

Persisting high LH levels (pregnancy)