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Yr 2 - Reproductive System > Intro and Menstrual Cycle > Flashcards

Intro and Menstrual Cycle Flashcards

1
Q

What is the purpose of the menstrual cycle?

A
  • Generate oocyte
  • Facilitate fertilisation
  • Optimise endometrium for implantation
  • Protect developing embryo
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2
Q

What is the endocrine control of the menstrual cycle?

A

Hypothalamus, anterior pituitary and ovaries work together

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3
Q

What is the name of the first menstrual cycle?

A

Menarche

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4
Q

What does the hypothalamus release during menstrual cycle?

A

GnRH

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5
Q

How does GnRH act?

A

Exerts effect on anterior pituitary –> stimulates release of FSH and LH

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6
Q

What does LH stand for?

A

Luteinising hormone

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7
Q

What does FSH stand for?

A

Follicular stimulating hormone

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8
Q

What does FSH and LH act on?

A

Ovary to release oestrogens (this feeds back to hypothalamus and anterior pituitary)

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9
Q

What part of the hypothalamus is GnRH secreted by?

A

Mid basal hypothalamic neurons

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10
Q

How is GnRH transported to the pituitary?

A

Via hypophyseal portal blood system

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11
Q

What is GnRH secretion affected by?

A 
bereavement
anxiety
time zone
day/night duty
exercise
weight loss/gain
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12
Q

What cells of the anterior pituitary secrete FSH and LH?

A

Basophils

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13
Q

What type of molecules are FSH and LH?

A

Glycoproteins

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14
Q

What does FSH stimulate?

A

Stimulates follicular activity, thus promoting estradiol production from granulosa cells

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15
Q

What does LH stimulate?

A

Triggers release of egg from dominant follicle

Promotes development of the corpus luteum and the production of progesterone

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16
Q

What is the predominant gonadotropin during the 1st half oF the cycle?

A

FSH

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17
Q

GnRH, LH and FSH production is inhibited by rising E2 levels.

When is there an exception to this?

A

Near midcycle when high levels of E2 lead to a surge in LH release which triggers ovulation

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18
Q

What E2?

A

Oestradiol –> Major female sex hormone (strongest of the 3 naturally produced oestrogens)

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19
Q

What are the first class of follicles formed in ovaries?

A

Primordial follicles

  • In fetus at 6 months: 2,000,000
  • At birth: 750,000
  • At puberty 400,000

Approx 450 follicles develop and produce an egg; remainder degenerate

No new follicles produced

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20
Q

Describe the sequence in which the egg is produced before ovulation

A
  1. Primordial follicle
  2. Primary/preantral follicle
  3. Secondary/antral follicle
  4. Preovulatory follicle
  5. Ovulation
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21
Q

What are the phases of the ovarian cycle?

A
  1. Follicular phase
  2. Ovulation
  3. Luteal phase
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22
Q

What is the follicular phase?

A

Marks the beginning of a new cycle as follicles (oocytes surrounded by stromal cells) begin to mature and prepare to release an oocyte.

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23
Q

What are follicular cells also known as?

A

Granulosa cells

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24
Q

Where do granulosa cells lie?

A

Directly around the oocyte zone pellucida and are released with the oocyte at ovulation

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25
Describe a primordial follicle
Cconsist of an oocyte surrounded by a single layer of flattened granulosa cells
26
Describe the follicular development
1. Proliferation of granulosa cells: antrum develops (fluid) 2. Gap junctions and cytoplasmic processes between oocyte and granulosa cells allows communication and passage of low mol wt materials (e.g.nutrients) 3. Proliferation of theca cells
27
What are theca cells?
The endocrine cells associated with ovarian follicles that play an essential role in fertility by producing the androgen substrate required for oestrogen biosynthesis.
28
Describe the theca interna cells
Glandular and highly vascularised. Express receptors for luteinising hormone (LH). Secrete androgens.
29
Describe the theca externa
Fibrous capsule
30
After the follicle ruptures, what do the theca interna cells differentiate into?
The theca lutein cells of the corpus luteum.
31
What are the androgens secreted by the theca interna cells converted to? Where?
Converted to oestradiol in granulosa cells
32
Describe the ovarian hormone production at the beginning of the cycle (menses)
There is little ovarian hormone production and the follicle begins to develop independently of gonadotropins or ovarian steroids.
33
What do the low steroid and inhibin levels at the beginning of the cycle cause? Why?
There is little negative feedback at the HPG axis resulting in an increase in FSH and LH levels. These stimulate follicle growth and oestrogen production.
34
What do almost mature follicles release? What does this then stimulate?
High levels of oestrogens Stimulates release of more GnRH and LH GnRH then promotes release of FSH and even more LH
35
How many follicles can continue to maturity? What do the other follicles form?
Only one Polar bodies
36
As follicular oestrogen eventually becomes high enough to initiate at the HPG axis, what happens?
Causes increasing levels of GnRH and gonadotropins. However, the effect is only reflected in LH levels (the LH surge).
37
What is the LH surge due to?
Due to the increased follicular inhibin, selectively inhibiting FSH production at the anterior pituitary. Granulosa cells become luteinised and express receptors for LH.
38
What is the HPG axis?
Connection between the hypothalamus, pituitary gland, and gonads.
39
Describe the production of inhibin
FSH stimulates the secretion of inhibin from the granulosa cells of the ovarian follicles in the ovaries. In turn, inhibin suppresses FSH
40
What does the LH surge bring about?
Ovulation
41
What happens to the follicle in response to the LH surge?
It ruptures and the mature oocyte is assisted to the fallopian tube by fimbria. Here it remains viable for fertilisation for around 24 hours.
42
Following ovulation, what does the follicle secrete?
Secreting oestrogen and now also progesterone
43
What is the effect of the secretion of oesotrogen and progesterone by the follicle? What is purpose of this?
-ve feedback on HPG axis This, together with inhibin (inhibits FSH) stalls the cycle in anticipation of fertilisation.
44
What is the corpus luteum? What does it produce?
The tissue in the ovary that forms at the site of a ruptured follicle following ovulation. It produces oestrogens, progesterone and inhibin to maintain conditions for fertilisation and implantation.
45
If no fertilisation occurs, what happens to the corpus luteum?
Degenerate/fibroses to become corpus albicans
46
As the corpus luteum regresses, what happens to the hormone levels?
Fall significantly, relieving negative feedback, resetting the HPG axis ready to begin the cycle again.
47
What is the endometrium?
The lining layer of the uterus
48
What are the phases of the uterine cycle?
1. Proliferative phase (runs alongside follicular phase) 2. Secretory phase (runs alongside luteal phase) 3. Menses
49
What does menses mark?
Beginning of new menstrual cycle
50
Describe the endometrium during the proliferative phase?
Effects of oestradiol: - Endometrium thickens - Increased stromal cels - Increased glands, blood vessels By ovulation, endometrium is 2-3mm thick
51
What else does oestradiol initiate during proliferative phase?
Fallopian tube formation, thickening of the endometrium, increased growth and motility of the myometrium and production of a thin alkaline cervical mucus (to facilitate sperm transport).
52
What else does oestradiol initiate during proliferative phase?
Fallopian tube formation, thickening of the endometrium, increased growth and motility of the myometrium and production of a thin alkaline cervical mucus (to facilitate sperm transport).
53
What is the predominant hormone during the 2nd half of the cycle?
Progesterone
54
Describe the secretory phase
Progesterone stimulates further thickening of endometrium Increased secretion Increased lipids and glycogen Increased blood supply
55
Describe the endometrium at the end of the secretory phase
Optimal conditions for implantation of fertilised egg: stable, vascular, nutrient-rich
56
What happens during menstruation?
Corpus luteum has broken down and the internal lining of the uterus is shed
57
How does the uterus lining shed?
Necrotic outer layers of endometrium separate from uterus Separated tissue and blood initiate uterine contractions --> expel contents
58
What is produced by the cervix?
Mucus production from columnar glands
59
Describe the mucus produced by the cervix midcycle? What is purpose of this?
Stringy and runny midcycle Facilitates sperm access at ovulation
60
Describe the mucus produced by the cervix in the luteal phase? What is purpose of this?
Tenacious and inelastic in luteal phase - Prevents microbial ingress protects developing embryo - Critical to pregnancy (mucus ‘plug’)
61
What does the combined oral contraceptive contain?
Oestradiol and a progestagen
62
What is progestagen?
A synthetic progesterone
63
What does the combined oral contraceptive do?
Inhibits GnRH/FSH/LH to prevent ovulation. Thin endometrium. Tenacious and inelastic mucus.
64
Describe the effects of FSH in the menstrual cycle
Binds to granulosa cells to stimulate follicle growth, permit the conversion of androgens (from theca cells) to oestrogens and stimulate inhibin secretion
65
Describe the effects of LH in the menstrual cycle
LH acts on theca cells to stimulate production and secretion of androgens
66
What are the effects of moderate oesotrogen levels on the HPG axis?
Negative feedback
67
What are the effects of high oesotrogen levels on the HPG axis (in the absence of progesterone)?
Positively feedback on the HPG axis
68
What are the effects of oesotrogen on the HPG axis in the presence of progesterone?
Negative feedback on the HPG axis
69
What are the effects of inhibin?
Selectively inhibits FSH at the anterior pituitary
70
What is only hormone with positive feedback effect on HPG axis?
Oestrogen (LH surge)
71
What day is ovulation?
Around day 14
72
What is the Tanner Scale?
Scale of physical development in children, adolescents and adults (puberty scale)
73
How many stages are there in the Tanner Scale?
5
74
Describe stage 1 in Tanner Scale
Preadolescent, no sexual hair No boobs for females
75
Describe stage 2 in Tanner Scale
Sparse, pigmented, long straight hair along labia and at base of penis Breast budding (areola and papilla)
76
Describe stage 3 in Tanner Scale
Darker, coarser, curlier hair Continued enlargement of breats
77
Describe stage 4 in Tanner Scale
Adult but decreased distribution (hair) Areola and papilla form secondary mound
78
Describe stage 5 in Tanner Scale
Adult in quantity and type with spread to medial thighs Mature female breast

Yr 2 - Reproductive System (30 decks)

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