Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

ESA 4 - Reproductive System > Oogenesis and the Ovarian Cycle > Flashcards

Oogenesis and the Ovarian Cycle Flashcards

1
Q

When does maturation of oocytes begin?

A

Before birth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where do germ cells arise from?

A

The yolk sac

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens after germ cells have arisen from the yolk sac of the female?

A

They colonise the gondal cortex and differentiate into oogonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens once germ cells have differentiated into oogonia?

A

They proliferate rapidly by mitosis, and some enter meisois

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is oogonias entry into meisois 1 stimulated by?

A

Mesonephric cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are mesonephric cells?

A

Flattened epithelial cells, also called Follicular Cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to the oogonia in meisosis 1?

A

They arrest in the diplotene stage (a resting stage) of prophase 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What causes oogonia to arrest in the diplotene stage of prophase 1?

A

Due to Oocyte Maturation Inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What secretes Oocyte Maturation Inhibitor?

A

Follicular cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the oogonias that are arrested in the diplotene stage now known as?

A

Primary oocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When is the maximum number of germ cells reached?

A

Mid-gestation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens to the number of germ cells at mid-gestation?

A

Cell death begins, and many oogonia and primary oocytes degenerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the process of degeneration of oogenia and primary oocytes known as?

A

Atresia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What has happened to the oogonia by the 7th month of gestation?

A

The majority of oogonia have degenerated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How many primary oogonia survive by the 7th month of gestation?

A

˜2 million

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What has happened all surviving primary oocytes by the 7th month of gestation?

A

They have entered meisosis I, and are surrounded by a flat layer of epithelial cells- follicular cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the primary oocytes surrounded by follicular cells now called?

A

Primordial follicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How long to the primordial follicles remain in meiosis I?

A

At least until puberty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens to most oocytes during childhood?

A

Most undergo atresia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How many oocytes remain by puberty?

A

˜40,000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the clinical relevance of a woman having all the oocytes she will ever have at birth?

A

Some may remain arrested for 50 years before further development, increasing the chance of cell damage and thus accounting for the increased risk of foetal chromosomal abnormalities in pregnancies of older women

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What happens to oocytes from puberty onwards?

A

˜15-20 oocytes start to mature each month

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What stages do oocytes go through when maturing?

A
  1. Pre-antral
  2. Antral
  3. Pre-ovulatory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens in the pre-antral stage of maturation?

A
  • Primary oocyte grows dramatically, but does not re-start meiosis
  • Flat follicular cells become cuboidal Granulosa cells, and proliferate, producing stratified epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What do Granulosa cells do in the pre-antral stage?
Secrete glycoprotein
26
What is the purpose of the glycoprotein secreted by the Granulosa cells in the pre-antral stage?
It surrounds the oocyte with a Zona Pellicuida
27
What do surrounding connective tissue (stroma) cells form in the pre-antral stage?
A Theca Folliculi
28
What does the Theca Follucli consist of?
* An inner Theca Interna * An outer Theca Externa
29
What are the characteristics of the Theca Interna?
* Vascular * Endocrine
30
What is the Theca Externa?
A fibrous capsule
31
What do Theca and Granulosa cells collaborate to do?
Secrete oestrogens
32
33
What is the primary oocyte known as after the pre-antral stage?
Primary follicle
34
What happens in the Antral stage of maturation?
Granulosa cells continue to proliferate, and a fluid appears between them
35
What does the appearance of fluid between the granulosa cells in the antral stage form?
The **antrum**
36
What happens as more fluid forms in the Antral stage?
The secondary, or Graffian, follicle expands
37
How big does the secondary follicle expand to in the Antral stage?
2mm in diameter, *without stimulation from reproductive hormones*
38
What does continued development of the secondary follicle, past 2mm, depend on in the Antral stage?
Reproductive hormones
39
What reproductive hormones are required to continue the development of the antrum in the Antral stage?
* FSH * LH
40
What does FSH bind to in the Antral stage?
The Granulosa cells **only**
41
What does LH bind to in the Antral stage?
Thecal cells **only**
42
What do Thecal cells do under the influence of LH?
Secrete androgens
43
What happens to the androgens secreted from the Thecal cells?
They are converted to oestrogens by Granulosa cells
44
What is the conversion of androgens to oestrogens by the Granulosa cells under the influence of?
FSH
45
When does the Pre-ovulatory phase begin?
37 hours before ovulation
46
What happens in the Pre-ovulatory stage?
Oestrogen causes receptors for LH to appear on outer Granulosa cells
47
What stimulates the LH receptors on the outside of Granulosa cells in the Pre-ovulatory stage?
LH surge
48
What is the result of the stimulation of the receptors on the outer Granulosa cells by the LH surge?
Rapid changes in the follicle
49
What happens within 3 hours of the LH surge?
The follicle restarts meiosis, and the first meitoic division is complete
50
What is true of the first meiotic division in the pre-ovulatory stage?
It is asymmetric
51
What is meant by the first meiotic division in the pre-ovulatory stage being asymmetric?
Cytoplasm remains with one daughter cell, and the other forms a condensed polar body
52
What happens after the first meiotic division in the pre-ovulatory stage?
The secondary follicle enters meiosis II, and arrests again 3 hours prior to ovulation
53
What happens to the follicle in the pre-ovulatory stage?
It increases dramatically, to 25mm diameter
54
Why does the follicle size increase dramatically in the pre-ovulatory stage?
Due to increase in antral fluid volume
55
What happens once the follicle has increased in size in the pre-ovulatory stage?
The structure begins to weaken
56
What happens to the weakened structure in the pre-ovulatory stage?
LH stimulates collagease activity, leading to **follicle rupture**
57
What happens to the ruptured follicle?
The ovum is carried out in the fluid, and gathered up into the fallopian tube by the fimbria
58
When is meiosis completed in the pre-ovulatory phase?
When the ovum is fertilised *Not completed unless the ovum is fertilised*
59
What happens to unfertilised cells?
They degenerate 24 hours after ovulation
60
What promotes the development of the corpeus luteum?
LH
61
What happens in the development of the corpeus luteum?
* Remaining granulosa and theca interna cells become vascularised * Develop yellowish pigment and change into lutein cells
62
What does the corpeus luteum do?
Secretes oestrogen and progesterone
63
What is the purpose of the secretion of oestrogen and progesterone by the corpus luteum?
Stimulates uterine mucosa to enter secretory stage
64
What is the purpose of the stimulation of the uterine mucosa to enter the secretory stage?
It prepares for embyro implantation
65
What happens to the corpeus luteum if no fertilisation occurs?
Degenerates after 14 days
66
What happens in the degeneration of the corpus luteum?
* Forms corpus albicans * Progesterone production decreases
67
What is the corpus albicans?
A mass of fibrotic scar tissue
68
What does a decrease in progesterone production precipitate?
Menstrual bleeding
69
What happens to the corpus luteum if fertilisation occurs?
* Degeneration of CL prevented by human chorionic gonadotrophin * Corpus luteum continues to grow * Cells continue to secrete progrestone until about 4th month
70
What secretes human chorionic gonadotrophin?
The developing embryo
71
What does the continuation of growth of the corpus luteum when fertilisation occurs form?
The corpus luteum of pregnancy, the **corpus luteum graviditatis**
72
Why does the corpus luteum stop secreting progesterone at about the 4th month?
The secretion of progesterone by the placenta then becomes adequate
73
What is the role of LH and FSH in ovulation?
They stimulate the rapid growth of follicles several days before ovulation
74
What is the mature follicle called?
Graafian follicle
75
What does the LH surge cause?
* Increase in collagenase activity * Prostaglandin increase
76
What do prostaglandins cause in ovulation?
Local muscular contractions in ovarian wall, leading to the oocyte being extruded and breaking free from ovary
77
What happens in oocyte transport?
* Shortly before ovulation, fimbriae sweep over surface of ovary, and uterine tubes begin to contract rhymthically * Oocyte is carried into tube by sweeping movements of fimbriae, and by motion of cilia on epithelial linings * Oocyte then propelled by peristaltic muscular contractions of tube and cila in the mucosa
78
How long does it take for the oocyte to reach the uterine lumen if fertilised?
3 to 4 days

ESA 4 - Reproductive System (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions