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Flashcards in Gametogenesis Deck (66):
1

What is fecundity?

The potential for reproduction

1. Gamete production
2. Fertilisation
3. Carrying a pregnancy to term

2

What is fertility?

The measure of reproduction

1. Number of children born per person, couple or population

3

What is fertility rate?

The number of births per time period per person, couple or population

4

What causes cessation of fecundity in males?

1. Loss of libido
2. Erectile dysfunction (due to diabetes or vascular pathology)
3. Vascular pathology

5

What causes cessation of fecundity in females?

Menopause

6

What is the climacteric?

Period of life when fertility and sexual desire in women are in decline

7

What is amenorrhoea?

Lack of periods

Primary = no periods ever
Secondary = periods stop

8

What causes menopause?

1. Ovarian decline and failure
2. Fewer oocytes of lower quality leads to chromosomal anomalies
3. Follicular decline leads to hormone changes and secondary amenorrhoea

9

When does fecundity begin?

Puberty

Girls initiate puberty about 2 years earlier than boys

Average age of onset of puberty has been coming down, possibly due to artificial light

10

Where are the germ cells in the testis?

In seminiferous tubules

11

Where are the germ cells in the ovary?

In follicles

12

What are testicular germ cells called?

Spermatogonial stem cells

13

What are ovarian germ cells called?

Primordial oocytes

14

In what stage of differentiation are the testicular stem cells during fetal life?

Mitotic

15

In what stage of differentiation are the ovarian stem cells during fetal life?

Enter first meiotic division and arrest

16

How many testicular stem cells survive?

Most germ cells survive to adulthood

Large population of renewable cells remains at puberty

17

How many ovarian stem cells survive?

Most germ cells die at around the time of birth

Relatively few oocytes left by puberty

18

How many sperm are made per day?

30 million

19

What fluid are spermatozoa released in?

Testicular fluid

20

What fluid are oocytes released in?

Follicular fluid

21

What does inhibin do?

Inhibits FSH

In females, output rises pre-oocyte release and remains high after it

Produced by Sertoli cells and granulosa cells

22

What is the temperature in the testis?

4-7 degrees below body temperature

23

How does the testis maintain a lower temperature?

1. Position outside the body
2. Pampiform plexus cools arterial blood
3. Divided into compartments

24

What is the role of the blood/testis barrier?

Testis is a privileged site

1. Prevents penetration of tubular wall so that immune cells cannot gain access
2. Prevents penetration from basal component and adluminal compartment
3. Consequences of breakdown leads to autoallergic orchitis

25

What do Sertoli cells do?

Produce inhibin and testicular fluid

26

Where are the Leydig cells located?

Outside the tubules in the interstitium

27

Where does meiosis occur in spermatogenesis?

In the spermatocytes as they move from the basal to the luminal part of the tubule

28

What is spermiogenesis?

Maturation of round spermatids through elongating spermatids to spermatozoa

29

What is spermiation?

Release of spermatozoa luminally into testicular fluid

30

How long does spermatozoa production take?

64 days

31

How long is the interval of groups of spermatogonia initiating development?

16 days

32

Give four functions of androgens

1. Stimulate accessory sex gland growth and secretion in men
2. Stimulate secondary sex body hair patterns in both men and women
3. Exert anabolic and myotrophic effects to affect body shape
4. Metabolised in target tissues to forms with differential activity

33

What controls production of testicular androgen?

The pituitary gland

GnRH released from hypothalamus controls pituitary

34

What does hyphophysectomy cause?

Leydig cell regression

35

What precedes rise in androgens at puberty?

Rise in LH

36

Where does LH bind in the testes?

Receptors on Leydig cells

37

What are the gonadotrophins?

FSH and LH

38

What is the dictyate stage?

Prolonged resting phase when primordial oocytes arrest in meiotic prophase

39

Where does the oocyte develop?

Within a follicle

The oocyte-follicular unit

40

When is the major growth phase of the oocyte?

Primordial - preantral phase

10 --> 110µm diameter

41

What is the zona pellucida?

Glycoproteins secreted by oocyte during primordial - preantral phase

42

What do the stromal cells form?

Condense and form thecal cells

43

What triggers the primordial - preantral phase?

It is spontaneous

It does not depend on exogenous hormones nor does it produce hormones

44

Give four roles of the granulosa cells?

1. Follicular fluid secretion
2. Formation of an antrum within the follicle
3. Convert androgens to oestrogens in the presence of FSH
4. Produce inhibin

45

What is the cumulus oophorus?

Inner layer of corona radiata

Projects into antrum from granulosa cells

Connected to oocyte

46

What happens to the granulosa cells in the preantral - antral phase?

Develop FSH receptors

Require FSH

47

What happens to the thecal cells in the preantral - antral phase?

Develop LH receptors

Require LH

48

What is the role of thecal cells?

Androgen production under LH stimulation

49

How do oestrogens affect granulosa cells?

Bind and stimulate granulosa cells that made them

Positive feedback

50

What is the role of inhibin in the ovary?

1. Rising inhibin levels stimulate androgen output by thecal cells
2. Stimulate conversion to oestrogens by the granulosa cells

51

What happens to oestrogen in the pre-ovulatory follicle?

Positive feedback

Rapid increase in oestrogen output

52

What happens to the thecal layer in the pre-ovulatory follicle?

1. Becomes hyperaemic
2. Increased androgen output
2. Increased oestrogen output

53

What is the endocrine switch?

As follicle approaches ovulation, granulosa cells also develop LH receptors and start synthesising progesterone under LH stimulation

54

When does oocyte meiosis reactivate?

Pre-ovulatory follicle

High levels of LH

55

How is the secondary oocyte formed?

1. Prophase nuclear membrane breaks down
2. Oocyte enters MI, AI and TI as primary oocyte
3. First meiotic division is unequal and produces a small first polar body and large oocyte
4. Oocyte enters meiosis II

56

In what stage does the secondary oocyte arrest and ovulate?

Metaphase II

57

What triggers ovulation?

Large spike in LH

Prostaglandins also involved

58

Where does the follicle surface rupture?

The stigma

59

How is the oocyte released to the surface of the ovary?

In its cumulus oophorus carried in follicular fluid

60

What do the granulosa cells become following ovulation?

Large lutein cells

61

What do some of the thecal cells become following ovulation?

Small luteal cells

62

What is the corpus luteum?

The post-ovulatory follicle

63

What is the corpus luteum made of?

1. Large luteal cells
2. Small luteal cells

64

What do large luteal cells do?

1. Increase production of progesterone
2. Convert androgens to oestrogens
3. Secrete inhibin in large amounts

65

What do small luteal cells do?

1. Produce androgens
2. Pass androgens to large luteal cells

66

What hormone does the corpus luteum require?

hCG