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Gametogenesis Flashcards

1
Q

What is fecundity?

A

The potential for reproduction

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

What is fertility?

A

The measure of reproduction

  1. Number of children born per person, couple or population
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3
Q

What is fertility rate?

A

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

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4
Q

What causes cessation of fecundity in males?

A
  1. Loss of libido
  2. Erectile dysfunction (due to diabetes or vascular pathology)
  3. Vascular pathology
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5
Q

What causes cessation of fecundity in females?

A

Menopause

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6
Q

What is the climacteric?

A

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

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7
Q

What is amenorrhoea?

A

Lack of periods

Primary = no periods ever
Secondary = periods stop
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8
Q

What causes menopause?

A
  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
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9
Q

When does fecundity begin?

A

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

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10
Q

Where are the germ cells in the testis?

A

In seminiferous tubules

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11
Q

Where are the germ cells in the ovary?

A

In follicles

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12
Q

What are testicular germ cells called?

A

Spermatogonial stem cells

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13
Q

What are ovarian germ cells called?

A

Primordial oocytes

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14
Q

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

A

Mitotic

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15
Q

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

A

Enter first meiotic division and arrest

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16
Q

How many testicular stem cells survive?

A

Most germ cells survive to adulthood

Large population of renewable cells remains at puberty

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17
Q

How many ovarian stem cells survive?

A

Most germ cells die at around the time of birth

Relatively few oocytes left by puberty

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18
Q

How many sperm are made per day?

A

30 million

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19
Q

What fluid are spermatozoa released in?

A

Testicular fluid

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20
Q

What fluid are oocytes released in?

A

Follicular fluid

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21
Q

What does inhibin do?

A

Inhibits FSH

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

Produced by Sertoli cells and granulosa cells

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22
Q

What is the temperature in the testis?

A

4-7 degrees below body temperature

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23
Q

How does the testis maintain a lower temperature?

A
  1. Position outside the body
  2. Pampiform plexus cools arterial blood
  3. Divided into compartments
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24
Q

What is the role of the blood/testis barrier?

A

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
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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

Human Reproduction (17 decks)

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