Origins of Gametes - Female Gamete Flashcards Preview

ESA 4 - The Reproductive System > Origins of Gametes - Female Gamete > Flashcards

Flashcards in Origins of Gametes - Female Gamete Deck (21)
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1
Q

What part of the gonad do germ cells colonise?

And what do they become?

A

The gonadal cortex

They become oogonia

2
Q

Once the germ cells have colonised the gonads and produced oogonia, what do they do?

A

They proliferate rapidly by mitosis

3
Q

When do oogonia reach max number?

A

Mid gestation (7 million)

4
Q

What happens to most oogonia during gestation?

And what happens to the rest before birth?

A

Most die, normally about 2 million remain

The remaining 2 million all enter meiosis before birth

5
Q

Describe what initially happens to the oogonia which have started meiosis?

A

Meiosis stops at an early stage
These are now primary oocytes
They are surrounded by a singular layer of granulosa cells
forming primordial follicles

6
Q

What happens at puberty to the female gametes?

A

The follicles start to develop further

Only a small proportion develop at a time

7
Q

What happens to most developing gametes in a woman’s reproductive life?

A

Most die

Only about 400 or so survive and are released in a woman’s life out of 2 million

8
Q

What is the term for release of an ovum?

A

Ovulation

9
Q

How long is the period of fertility in a woman?

A

About 36 hours after the release of an ovum

10
Q

What is the human female reproductive cycle known as?

A

The menstrual cycle

11
Q

How long is the menstrual cycle?

A

Around 28 days

12
Q

What are the three main parts of the menstrual cycle?

And give a time period for each

A

Preparatory phase - days 0-12
Ovulation - around days 12-14
Waiting phase - days 14-28

13
Q

What is the preparatory phase known as in regards to the ovaries and uterus?

A

Ovaries - Follicular phase

Uterus - Proliferative phase

14
Q

What is the waiting phase known as in regards to the ovaries and uterus?

A

Ovaries - Luteal phase

Uterus - Secretory phase

15
Q

What happens at the beginning of the menstrual cycle?

A

A small number of gametes that have already started development begin to develop further

16
Q

At the beginning of the menstrual cycle primordial follicles develop into what?

A
Pre-antral follicles
The granulosa cells proliferate
A layer called the zona pellucida forms around the oocyte
Then lots of granulosa cell layers
And a final covering called a theca
This all happens independent of hormones
17
Q

What turns a pre-antral follicle into an antrum?

A

The formation of a small fluid filled cavity in the follicle.

18
Q

After an antrum forms what happens to the follicles?

A

Under the influence of FSH and LH one or two follicles grow to 20mm
Then the theca secretes oestrogen
This is a pre-ovulatory follicle

19
Q

After the mature follicle is formed, just before ovulation, what happens?

A
Meiosis restarts (continues)
This forms 2 daughter cells but only one is functional, it has all the cytoplasm, the other is just a packet of DNA that is discarded
This is the first division
20
Q

When does the second division of the oocyte occur?

A

After fertilisation

21
Q

What happens to the follicle after the oocyte has been released?

A

It forms a corpus luteum
Which grows under influence of LH
Secretes oestrogen and progesterone
And if it doesn’t receive a signal that the ovum has been fertilised, it kills itself.