The Menstrual Cycle - Reproduction 2

Question 1

Events associated with ovarian cycle
Events associated with uterine cycle
Role of hormones (FSH, LH, oestrogen,
progesterone) in each phase of the cycle

Question 2

Key Learning Objectives:
* Understand the ovarian and uterine cycles
* What major processes are occurring during
both
* Hormonal regulation

Question 3

Menstrual cycle includes 2 cycles which are?

Answer 3

Ovarian and uterine

Question 4

What is the Ovarian cycle?

Answer 4

Controls production and release of
eggs, the cyclic release of estrogen and
progesterone

Question 5

Uterine cycle - what is it?

Answer 5

Controls the preparation and maintenance of the lining of the uterus to receive an embryo

Question 6

Average menstrual cycle lasts?
Normally only interrupted by?
Terminated by?

Answer 6

28 days
Pregnancy
Menopause

Question 7

Ovarian cycle what are the 2 phases?

Answer 7

Follicular and luteal phases

Question 8

See slide 4 diagram
Ovarian cycle phases are separated by?
This occurs at what day of cycle?

Answer 8

Ovulation which typically occurs at day 14

Question 9

What is Folliculogenesis?

Answer 9

The process by which a follicle forms, proceeds through several growing stages, develops to eventually release the mature oocyte, and turns into a corpus luteum

Question 10

Before birth, each primary oocyte is surrounded by what?
What is this called?

Answer 10

A single layer of connective tissue derived granulosa cells
Primordial follicle

Question 11

Folliculogenesis takes place where?

Answer 11

In the cortex of the ovary

Question 12

When does folliculogenesis occur in a female’s life?

Answer 12

Continually from fetal life until menopause

Question 13

What do almost all follicles under go at some stage?

Answer 13

Atresia which is death of the ovum, followed by collapse of follicle

Question 14

Preantral follicles are Gn independent and go through different phases: Primordial, primary and secondary - explain these?

Answer 14

– Primordial – Dormant, 1 layer of granulosa cells
– Primary – Growing, 1 layer of cuboidal granulosa cells, granulosa cells begin to express FSH receptor, oocyte growth (~25 µm to ~120 µm), oocyte and granulosa cells secrete glycoproteins that form a thick gel rind around the oocyte seperating it from surrounding granulosa cella - the zona
pellucida)
– Secondary – Growing, 2+ layers of cuboidal granulosa cells, theca emerges (stromal-like cells around the basal lamina, interna and externa) accompanied by development of small blood vessels in the theca

Question 15

Mechanisms involved in the initiation of the growth of the preantral follicles up to the pre-ovulatory stage, are not well understood at this time

Question 16

Takes how long for primordial follicle to develop into early antral follicle?

Answer 16

About 1 year ~300 days

Question 17

Antral follicles are Gn (Gonadotropin hormone) dependent include what follicles?

Answer 17

Teritary -> antrum starst to develop
Preovulatory/Graafian -> as they further divide they become this

Question 18

Time from antrum formation to development of a 20mm preovulatory follicle is how many days?

Answer 18

~60 days

Question 19

There are always a number of pre-antral
and early antral follicles in the ovary between puberty and menopause – further maturation of the follicles requires what?

Answer 19

FSH (i.e. ↑ puberty)

Question 20

Onset of antrum development appears as what?

Answer 20

Appearance of a fluid filled cavity at one pole of the oocyte

Question 21

Slide 7 see diagram

Question 22

Follicular phase involves the development of maturing follicles - what happens?

Answer 22

Follicles are stimulated to mature, one follicle will fully mature and release ovum (ovulation)

Question 23

Follicular phase occurs at what point of ovarian cycle?

Answer 23

First 1/2

Question 24

Rate of granulosa mitosis appears to increase/decrease in follicular phase?

Answer 24

The rate of granulosa mitosis appears to increase sharply (~2 fold) in a cohort of follicles
after the mid-luteal phase.

Question 25

The first indication that selection has occurred during follicular phase is that? This effects is observed around what time?

Answer 25

The granulosa cells continue dividing at a relatively fast rate in one cohort follicle while proliferation slows in the granulosa of the other cohort follicles. This effect is observed about the time of menses.

Question 26

1. As the follicular phase proceeds, the selected “dominant” follicle grows slow or fast? 2. Reaching what size and when? 3. Growth proceeds faster or slower in the antral follicles during this time?

Answer 26

1. Rapidly 2. Reaching 18.8 ± 0.5 mm at days 11 to 14. 3. Conversely, growth proceeds more slowly in the other antral follicles of the cohort.

Question 27

Slide 9 see diagram Follicular phase what hormone is made? This is driven by what cells?

Answer 27

Oestrogen by the developing follicles Driven by cooperative actions of thecal cells and granulosa cells

Question 28

What hormone acts on thecal cell? What hormone acts on Granulosa cells?

Answer 28

LH FSH

Question 29

When LH acts on thecal cells what does this cause?

Answer 29

Stimulates thecal cells to convert Cholesterol into androgen which then diffuses from thecal cells into granulosa clles and is converted into estrogen

Question 30

1. Once estrogen is secreted into the blood what happens? 2. What about if estrogen remains in the follicle?

Answer 30

1. Secreted into blood 2. Contributes to antral formation

Question 31

FSH acts on granulosa cells to convert?

Answer 31

Androgen into estrogen

Question 32

See diagram slide 10 Expression of LH receptors is suppressed until?

Answer 32

Late in the follicular phase of the cycle

Question 33

Ovulation takes place on day 14 what type of follicle releases a mature egg and where is this enclosed within for possible fertilisation? Cumulus oocyte complex =?

Answer 33

Selected preovulatory follicle releases a mature egg enclosed within a cumulus complex for possible fertilisation (cumulus oocyte complex = oocyte, ZP, cumulus cells, polar body)

Question 34

Oocyte enters what?

Answer 34

Fallopian tube

Question 35

What are cumulus cells?

Answer 35

They are granulosa cells that surround the oocyte and support oocyte maturation and fertilisation

Question 36

Hormonal control for ovulation what surge is a trigger?

Answer 36

LH

Question 37

Ovarian cycle for the 2nd half is the luteal phase and this accounts for what days of the cycle?

Answer 37

The last 14 days

Question 38

What is the hormonal control of the luteal phase and what does it cause?

Answer 38

LH causes development of corpus luteum

Question 39

Old follicular cells under structural transformation during luteal phase to form what?

Answer 39

Corpus luteum which is a gland

Question 40

Corpus luteum makes?

Answer 40

Progesterone and oestrogen

Question 41

The corpus luteum during luteal phase becomes highly vascularised and continues to increase in size for how many days?

Answer 41

4-5 days

Question 42

If released and the ovum is not fertilised and does not implant what happens?

Answer 42

Corpus luteum degenerates within ~ 14 days after formation

Question 43

If the ovum is fertilised what happens?

Answer 43

Continues to provide progesterone for early pregnancy

Question 44

Slide 13 summary of events of the ovarian cycle

Question 45

At the same time that these events are occurring in the ovaries a cycle of events is occurring in the uterus as ?

Answer 45

It is getting ready to receive and nourish the ovulated oocyte Both are regulated via hormones

Question 46

Uterine cycle averages how many days?

Answer 46

28 DAYS

Question 47

3 PHASES OF UTERINE CYCLE?

Answer 47

1. Menstrual phase 2. Proliferative phase 3. Secretory/progestational phase

Question 48

Menstrual phase what happens with hormones?

Answer 48

Decreased oestrogen & progesterone

Question 49

Menstrual cycle what occurs to the body and how many days does it last?

Answer 49

Uterine lining is shed Lasts 5-7 days

Question 50

Proliferative cycle is assoaaited with what hormone?

Answer 50

Oestrogen

Question 51

Secretory or progestational phase what hormone is involved in this phase?

Answer 51

Progesterone

Question 52

Secretory or progestational phase what hormone what happens and what does it coincide with?

Answer 52

Coincides with luteal phase. Endometrium develops

Question 53

Proliferative phase what happens?

Answer 53

Endometrium renewed in preparation for possible pregnancy

Question 54

Menstrual phase is characterised by?

Answer 54

By discharge of blood and endometrial debris from vagina

Question 55

1st day of menstruation is considered?

Answer 55

Start of new cycle

Question 56

Menstrual phase coincides with what of ovarian cycle?

Answer 56

End of ovarian luteal phase and onset of follicular phase

Question 57

Menstrual cycle is triggered by?

Answer 57

Decreases oestrogen and progesterone

Question 58

Why do oestrogen+progesterone decrease thus leading to menstrual phase?

Answer 58

Hormones decrease when CL degenerates

Question 59

What is released during menstrual phase?

Answer 59

uterine prostaglandin

Question 60

Uterine prostaglandin causes what? This leads to what effect on blood supply and endometrium?

Answer 60

Vasoconstriction of endometrial vessels – Disrupts blood supply – Causes death of endometrium

Question 61

Release of uterine prostaglandin stimulates what and what does this help?

Answer 61

Stimulates mild rhythmic contractions of uterine myometrium which helps expel the menstrual cycle

Question 62

Proliferative phase begins ?

Answer 62

Begins concurrent with last portion of ovarian follicular phase

Question 63

Proliferative phases lasts from?

Answer 63

Lasts from end of menstruation to ovulation

Question 64

Proliferative phase - the uterus prepares for fertilised ovum what happens to the endometrium and oestrogen?

Answer 64

Endometrium starts to repair itself and proliferate under influence of oestrogen from newly-growing follicles Peak oestrogen levels trigger LH surge responsible for ovulation

Question 65

Secretory phase what happens with endometrium?

Answer 65

Prepares for implantation

Question 66

As the endometrium prepares for implantation- what happens to: 1. Blood supply? 2. Glands? 3. Secretory phase conditions are promoted by?

Answer 66

1. Blood supply increased 2. Glands enlarge and secrete glycogen-rich fluids 3. Secretory phase conditions promoted by progesterone

Question 67

CL makes large amounts of progesterone and oestrogen and progesterone converts endometrium to what?

Answer 67

Highly vascularised, glycogen-filled tissue

Question 68

Endometrial glands actively secrets what and what does this sustain?

Answer 68

Secretes glycogen which sustains embryo development

Question 69

If fertilisation and implantation does not happen in secretory phase what occurs to CL and what happens after?

Answer 69

Corpus luteum degenerates (hCG) New follicular phase and menstrual phase begin again

Question 70

Hormonal control of the cycle via what 6 hormones?

Answer 70

GnRH, FSH, LH, Inhibin, Oestrogen and progesterone

Question 71

GnRH is short for and is made where? FSH is made where and short for and develops what? LH is made where? stands for? Causes and develops? Inhibin is made where and causes what effect on FSH and LH from what? Oestrogen and Progesterone are made where?

Answer 71

GnRH (hypothalamus): Gonadotropin-releasing hormone FSH (pituitary): Follicle stimulating hormone growth and development of follicles LH (pituitary): Luteinising hormone causes ovulation development of corpus luteum Inhibin (granulosa cells in the ovaries) : decreases FSH, but not LH from AP Oestrogen and progesterone (follicles, corpus luteum)

Question 72

1. Oestrogens stimulates what development? 2. Oestrogens promotes? 3. Induces expression fo what receptors? 4. Responsible for what characteristics? 5. Causes what fro pregnancy?

Answer 72

1. Stimulate oogenesis and follicle development 2. Promote proliferative-phase uterine conditions 3. Induce expression of uterine progesterone receptors and Induce expression of granulosa cell LH receptors 4. Secondary sexual characteristics 5. Breast growth during pregnancy

Question 73

Progesterone promotes what conditions? It reduces? It suppresses? It promotes the growth of? Effect on milk production? During secretory phase of uterine cycle increased progesterone has what effect?

Answer 73

*Promotes secretory-phase uterine conditions * Reduces myometrial contractility * Suppresses uterine contraction during pregnancy * Promotes growth of glandular breast tissue but suppresses milk production * During secretory phase of uterine cycle ↑ progesterone = mucus thickness → ↓↓ sperm penetration

Question 74

Hormone effects on the uterus - uterine+ovarian cycle: 1. Days 1-5? 2. Days 6-13? 3. Days 15-28?

Answer 74

1. Menstruation 2. Proliferative phase - follicular 3. Secretory phase - luteal

Question 75

What happens days1-5?

Answer 75

Days 1-5 – Menstruation (steroids withdrawal) –regression of the corpus luteum ↓↓ Oe and P, spasm, necrosis and sloughing of endometrium

Question 76

What happens days 6-13?

Answer 76

Days 6-13 – Proliferative phase (follicular) (Oestrogen) – Endometrial proliferation, increased myometrial excitability/contractility

Question 77

Days 15-28? what happens?

Answer 77

Days 15-28 – Secretory phase (luteal) (Progesterone) – promotes secretory changes in the uterine endometrium. Growth of spiral arteries, accumulation of glycogen/lipids (nutrients) in glands, increase in viscous secretions, ↓ myometrial contractility

Question 78

LH surges? LH +FSH secreted from? Progesterone secreted from? Oestrogen secreted first from follicle and then?

Answer 78

Oestrogen secreted first from the follicle, then from the corpus luteum – Progesterone secreted from the corpus luteum – LH and FSH secreted from the anterior pituitary – LH surge at ovulation

Question 79

Slide 23 early follicular phase see diagram

Question 80

See slide 24 diagrams and pathways Regulation of hormone secretion - late follicular phase+ovulation 1. Just prior to the middle of the cycle (approximately day 14), the high level of estrogen causes? 2. Spike in LH causes? 3. Follicles that did not rupture?

Answer 80

1. FSH and especially LH to rise rapidly (estrogen begins to stimulate LH, opposite to normal), then fall. 2. Causes ovulation as granulosa cells now have LH receptors. 3. Degenerate and their eggs are lost. The level of estrogen decreases when the extra follicles degenerate

Question 81

See slide 25 with diagram: luteal phase 1. Effect of progesterone? 2. Surge in LH causes? 3. Negative feedback inhibits? 4. CL also makes what effect does this hormone have? 5. Low levels of LH+FSH? 6. Degeneration of CL?

Answer 81

1. Progesterone – stops the high level of estrogen from triggering 2. Another LH surge – increase in progesterone and lesser increase in estrogen results in negative feedback 3. Inhibits LH secretion and FSH - acts on both AP and HT ARC neurons 4. CL also produces inhibin – low levels of LH and FSH – inhibit further follicle maturation and ovulation during luteal phase. 5. Low levels of LH and FSH – inhibit further follicle maturation and ovulation during luteal phase. 6. Degeneration of CL – unleashes FSH. FSH induces additional FSH receptors on granulosa cells (expanding its own effects) and stimulates new LH receptors on granulosa cells – initiating LH responsiveness.