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Flashcards in Gametogenesis Deck (56)
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1

When do primordial germ cells form?

By the 2nd week of gestation

2

Where do primordial germ cells form?

In the yolk sac by the 2nd week

3

What are primordial germ cells

The cells which go on to develop into gametes

4

Describe the migration of primordial germ cells

From endodermal layer of the yolk sac into the embryo via the hindgut to the dorsal body wall to form the gonadal ridges

5

When do the gonadal ridges form?

By 6-8 weeks - they form on the dorsal body wall, stimulated by primordial germ cells deposited there

6

What is the role of somatic support cells in the formation of female genitalia?

They form the ovarian follicle cells

7

What is the role of somatic support cells in the formation of male genitalia?

They form the testis cords and eventually the Sertoli cells of the seminiferous tubules

8

What is the embryological origin of teratomas?

Teratomas form from primordial germ cells

9

When does differentiation of the primordial germ cells happen in males?

The PGCs become spermatogoonia once they reach the gonadal ridge but do not undergo meiosis until puberty

10

What are primordial germ cells called in females once they have been surrounded by the somatic support cells of the ovaries?

Oogonia

11

What are oogonia?

Female primordial germ cells (diploid cells)

12

What do oogonia become?

Primary oocytes (when they start to undergo meiosis)

13

What are primary oocytes?

An oogonia which has started to undergo meiosis. Meiosis is arrested in prophase 1 in diplotene phase until puberty

14

What do primary oocytes become?

Secondary oocytes (oocytes entering the second phase of meiosis)

15

When do primary oocytes mature into secondary oocytes?

At puberty

16

When does the secondary oocyte complete meiosis?

After it the egg has been ovulated and fertilised

17

How many eggs are present at birth?

1-2 million

18

How many eggs are present at puberty?

300,000

19

How many eggs are present in a 20 week female fetus?

6-7 million (they degenerate from this point onwards

20

Which gene determines whether a primordial germ cell will differentiate into an egg or a sperm?

SRY gene on the Y xsome, if present the cells will turn into male gametes

21

What is a primordial follicle?

A female gamete surrounded by a thin layer of granulosa cells and an external basal lamina

22

What is a primary follicle?

A gamete surrounded by a thick layer of granulosa cells and a basal lamina

23

Which layer of the follicle is vascular?

The inner thecal layer

24

What is the Antral phase?

When the ovarian follicle forms a fluid filled cavity called the Antrum and a subset of granulosa cells surround the oocyte to form the cumulus oophorus

25

Which follicle cells develop FSH receptors?

The granulosa cells

26

Which follicle cells develop LH receptors?

Thecal cells

27

Which follicle cells produce testosterone and progesterone?

Thecal cells in response to LH

28

Which follicle cells produce estradiol?

Granulosa cells under the influence of FSH by converting testosterone from thecal cells to estradiol with aromatase enzyme

29

When are follicles dependent on hormones for development?

Once the Antrum forms

30

What is a secondary follicle?

An egg surrounded by a zona pellucida, granulosa cells, thecal cells