The menstrual cycle L5 Flashcards
(114 cards)
1
Q
endocrine control involves 3 things
A
neuropeptides
glycoproteins
steroids
2
Q
what is the neuropeptide involved in endocrine control
A
GnRH
3
Q
what is GnRH
A
gonadotropin releasing hormone
4
Q
where is GnRH released from
A
the hypothalamus
5
Q
structure of GnRH
A
decapeptide (10 aa)
6
Q
where does GnRh bind
A
to GnRH receptors expressed in the anterior pituitary gland
7
Q
3 main glycoproteins controlling endocrine function
A
LH (luteinizing hormone)
FSH (Follicle stimulating hormone)
CG Chorionic gonadotropin
8
Q
what are all three glycoproteins
A
heterodimers
9
Q
what is the key difference in FSH and LH
A
share the same alpha chain but different beta chains
10
Q
what does the difference in beta chains between FSH and LH mean
A
they can act on different receptors
11
Q
what also acts on the LH receptor
A
CG
12
Q
what type of receptors are the LH and FSH
A
G protein coupled receptors
13
Q
whats the common biochemical pre-cursor for steroids
A
cholesterol
14
Q
what is cholesterol made from
A
acetate
15
Q
four classes of steroids
A
progestogens
androgens
Oestragens
corticosteroids
16
Q
how many carbons does progestogens have
A
21
17
Q
how many carbons do androgens have
A
19
18
Q
how many carbons do oestragens have
A
18
19
Q
what is the common synthetic pathway for steroids
A
acetate—>cholesterol—> common precursor pregneolone
20
Q
what class is pregneolone
A
progestogen
21
Q
what is the precursor of the oestragens
A
androgens
22
Q
where does cholesterol synthesis take place
A
mitochondria
23
Q
how do neuropeptides and glycoproteins act
A
on specific receptors
24
Q
how do steroids act
A
can go directly through the nucleus
25
biggest sex organ=
brain
26
how often is GnRH released after puberty
in hourly pulses
27
what cells does GnRH act on
gonadotrophs
28
what are Oocytes contained in
pre-ovulatory follicles
29
when is Oocyte number fixed
at birth
30
how many eggs do we have at birth
2 million germ cells
31
what happens in the absence of the SRY gene
the coelomic epithelia condense around the PGC forming primordial follicles making them stop mitosis
32
what happens when the primary follicles stop mitosis and begin meiosis
the numbers are fixed
33
what stage of meiosis do the primary follicles arrest in
half way through meiosis 1 --> DIPLOTENE (prophase 1)
34
what are they called when they arrest in diplotene
primary oocyte
35
what happens to many primary follicles before birth
they die
36
at what point in development are there no more PGC being produced
after 3 months post conception
37
when does proliferation by mitosis happen
all completed by birth
38
when does genetic shuffling by meiosis happen
starts in fetal ovary, arrests and restarts at puberty
39
when does cytodifferentiation happen (making a specialised cell)
completed during ovarian cycle
40
in a preadolescent what is the hypothalamus like
immature hypothalamus releases slow pulses of GnRH
41
what do the slow pulses of GnRH from an immature hypothalamus mean
minimal FSH and LH production from pituitary so
no spermatogenesis in male
no ovarian follicle development in females
so.....no testosterone or oestradiol
42
what is a primordial follicle
primary oocyte
| surrounded by a single layer of granulosa cells
43
what happens to primordial follicles at puberty
they begin to grow
44
what does the primordial follicle grow to form
primary follicle
45
the difference in primordial follicles and primary follicle
primary follicle produces thick glycoprotein coat= Zona pellucida
46
what does the primary follicle form into
preantral follicle
47
what is the preantral follicle characterised by
proliferation of the granulosa cell
48
how are a lot of follicles lost
by atresia (degeneration of immature follicles)
49
What can rescue follicles from atresia
LH and FSH
50
what does the preantral follicle form
the antral follicle
51
what is the antral follicle characterised by (3)
the appearance of the antrum
proliferation of granulosa cells
theca cell present
52
what is the antrum
fluid filled cavity
53
three types of cell in the antrum=
Oocyte
theca cell
granulosa cells
54
what are the major hormones regulating female reproductive cycle (3)
FSH
LH
GnRH
55
when is the Oocyte number fixed
3 months post conception
56
what is the name of the structure unit in which the oocyte develops
the follicle
57
at what stage of development are Oocytes at birth
arrested in prophase 1 primary oocytes residing in primordial follicles
58
what is the pattern of GnRH release in the prepubertal female
irregular
59
what is the pattern of GnRH release in the postpubertal female
hourly intervals
60
at what stage of follicle development does ovulation occur
tertiary, preovulatory
61
how many phases does the ovarian cycle have
2
62
what are the 2 phases of the ovarian cycle
luteal
| follicular
63
what characterises the luteal phase
progesterone
64
in the follicular phase what hormone is released first
GnRH
65
What does GnRH do
cause secretion of FSH and LH from anterior pituitary
66
What cells have receptors for LH
Theca cells
67
what cells have receptors for FSH
granulosa cells
68
what does the binding of LH to theca cells cause
the synthesis of androgens
69
what do the granulosa do with the androgens from the Theca cells
make oestrogens using aromatase
70
whats is the oestrogen called that the granulosa cells make
Oestrogen 217 beta
71
where is Oestrogen 217 beta (E217B) released
into the plasma but with a short half life
72
what does E217B (oestrogen) do
acts on the anterior pituitary and hypothalamus in a negative feedback loop to regulate LH and FSH production
73
what other substance do the granulosa cells produce
inhibin B
74
What does inhibin B do
inhibits the production of FSH from the anterior pituitary
75
what effect do the androgens have on the granulosa cells
cause proliferation increasing the number of granulosa cells so the follicle grows
76
in females when is AMH produced and why
post puberty, to regulate the growth of neighbouring follicles
77
When a follicle expresses FSH and LH receptors that are acted upon what does it become
the dominant follicle that suppressing follicles around it
78
what does the sharp increase in granulosa cells cause
a sharp rise in oestrogen levels---> plasma oestrogen surge
79
how does oestrogen act on granulosa cells
in response to high oestrogen levels granulosa cells express LH receptors
80
when Oestrogen is in very high levels and reaches the threshold what happens
stops negatively inhibiting LH and FSH causing a peak in LH levels
81
what does the peak in LH levels do
triggers ovulation
82
what does the peak in LH levels do (2)
triggers ovulation
| progesterone production in granulosa cells
83
overall when E2 is low it does
negative feedback
84
overal when E2 is high it does
positive feedback
85
whats it called when the oocyte resumes meiosis and undergoes division
nuclear maturation
86
how would you describe the division in nuclear maturation
unequal, most cytoplasm retained in secondary oocyte
87
how much chromosome is lost on the 1st polar body in meiosis
half
88
what does the presence of a polar body in an oocyte mean
the oocyte is ready to be fertilised
89
in second meiosis when does the oocyte arrest
metaphase
90
what happens in oocyte maturation
```
cytoplasmic maturation (reorganised)
-mitochondria and cortical granules relocate to periphery
```
91
what happens at the same time as oocyte maturation
associated granulosa cells expand
92
what is it called when granulosa cells expand
cumulus cell expansion
93
what happens at the start luteal phase
ruptured follicle forms corpus luteum
94
what does the corpus luteum secrete
oestrogen and progesterone
95
how many days does the luteal phase last
14
96
what happens in the corpus luteum
all the cells of the corpus luteum now express LH receptor, production of oestrogen and rising levels of progesterone ----> negative LH feedback
97
what happens to the luteal phase after 14 days
it stops unless there is fertilisation and corpus luteal degrades
98
leutolysis=
break down of the corpus luteum
99
three stages of the uterine cycle
menstrual phase
proliferation phase
secretory phase
100
what happens in the menstrual phase
shedding of uterine lining
101
what happens in the proliferation phase
endometrium and myometrium begin to regrow
| increase cervical mucal secretions
102
what happens in the secretory phase
- blood supply to the endometrial tissues remodelled
- Cervical secretions change again
- supported by progesterone
103
how many days does it take for the epithelium to be re-epithelialized
4-7 days after the beginning of menstruation
104
what do progesterones do to the endometrium
cause swellings and secretory development of the endometrium (prepared for implantation)
105
what is menstruation caused by
the absence of a pregnancy
106
what is the most potent oestrogen
17-b estradiol
107
where does 95% of oestrogens come from
granulosa cells
108
when happens when you run out of eggs
you run out of oestrogen
109
what are menopausal symptoms principally caused by
lack of oestrogen
110
example of 3 menopausal symptoms
sleep disturbance
menstrual irregularity
hot flushes
111
3 long term problems with menopause
osteoporosis
dry vagina
alzheimer's
112
In HRT what is oestrogen usually prescribed with and why
progesterone
| because oestrogen alone stimulate endometrial hyperplasia and carcinoma
113
who can take oestrogen only pills
women who have has a hysterectomy
114
risk of HRT (4)
thrombosis
breast cancer
cardiac disease (older women)
Alzheimers
