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Reproductive system > Session 2 - Part II > Flashcards

Session 2 - Part II Flashcards

1
Q

What happens in the Preparatory phase of the Menstrual cycle?

A

Follicles grow in the ovary
Uterus prepares for sperm transport & implantation
Changes to facilitate sexual interactions
Also called Follicular/Proliferative phase

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2
Q

What happens in the Ovulation phase of the Menstrual cycle?

A

Brief period of fertility (Around 36 hours)

Formation of the Corpus Luteum

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3
Q

What happens in the Waiting phase of the Menstrual cycle?

A

Corpus Luteum in the ovary
Changes in preparation for pregnancy
Also called Luteal (Ovary) or Secretory (Uterus) phase

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4
Q

What does species variation show us?

A

That ovulation can be very precisely linked to the environment

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5
Q

What are Induced Ovulators?

A

There is no ovulation without copulation

eg cats & rabbits

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6
Q

What are Induced Waiting phase?

A

Spontaneous ovulation

No Corpus Luteum formed without copulation

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7
Q

What is unique about the Menstrual cycle in higher primates only?

A

They always ovulate and always have a waiting phase.

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8
Q

How is the Menstrual cycle ended?

A

Shredding of part of the endometrium

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9
Q

What hormones co-ordinate the Menstrual cycle?

A

Gonadotrophins (LH & FSH)
Gonadal steroids
Oestrogen
Progesterone

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10
Q

What is the level of FSH on day 0 of the Menstrual cycle?

A

High

They then fall after the Preparatory phase

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11
Q

When is the lowest level of FSH in the Menstrual cycle?

A

In the waiting phase

Peak for ovulation

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12
Q

What is the level of LH on day 0 of the menstrual cycle?

A

Low

Increase for LH surge then drop again

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13
Q

What are the actions of Gonadotrophins in the Follicular phase?

A

FSH binds to Granulosa cells
LH binds to Thecal cells in the Theca interna (Secretes Androgens which is then converted to Oestrogen then released)
Stimulates the development of the follicle

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14
Q

What are the actions of Gonadotrophins in the Pre-ovulation phase?

A

LH surge stimulates ovulation

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15
Q

What are the actions of Gonadotrophins in the Luteal phase?

A

LH maintains the Corpus Luteum

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16
Q

How does LH cause ovulation?

A

At very high levels it breaks down collagen in the Theca externa. This causes it to burst and the ovum is released
Usually happens due to LH surge

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17
Q

What are the actions of the Gonadal steroids in the Follicular phase?

A

Oestrogens stimulate -
Fimbrae in the fallopian tube to move the ovum
Endometrium to thicken
Vaginal changes
Changes in metabolism (And calcium metabolism)
A nutrient fluid produced to allow the sperm to fertilise the ovum
Cervical alkaline mucus, the sperm sticks to this

18
Q

What are the actions of the Gonadal steroids in the Luteal phase?

A

Progesterone acts on the Oestrogen primed cells -
Endometrium thickens further (Myometrium thicker but with decreased motility)
Increased body temperature
Changes to mammary tissue
Change in electrolyte & fluid balance

19
Q

What is the state of the ovum at the beginning of the Menstrual cycle?

A

The Corpus Luteum is absent

The follicles are only part developed

20
Q

What is low at the beginning of the Menstrual cycle?

A

Steroids & Inhibin
Oestrogen & Progesterone
Due to no theca or follicle to secrete it

21
Q

What is high at the beginning of the Menstrual cycle?

A

FSH & GnRH

Due to low levels of Inhibin

22
Q

How does FSH effect follicular development?

A

It binds to Granulosa cells which causes follicular development to continue
A Theca interna develops which can then secrete oestrogen (stimulated by LH) Inhibin is also released which acts on the Anterior Pituitary gland to reduce FSH levels

23
Q

How are more follicles prevented from developing during the mid follicular phase?

A

The oestrogen levels are rising (Positive feedback for LH)

Inhibin levels are rising (Selectively inhibits FSH)

24
Q

How does positive feedback of Oestrogen change the follicle?

A

It causes the follicle to become more developed and it gets closer to ovulation.

25
Q

How does Oestrogen indirectly cause ovulation?

A

It reaches a threshold value
This causes a great increase in GnRH
Huge increase in LH (LH surge) which breaks down Theca externa for ovum to be released

26
Q

How is the LH surge effected by environmental factors?

A

They can effect the precise timing of when it occurs once oestrogen has reached its threshold value (creating a ‘window of opportunity’ for ovulation)

27
Q

How can stress effect ovulation?

A

Delays it

28
Q

How can copulation effect ovulation?

A

Ovulation occurs sooner if copulation occurs very soon after the increase in oestrogen levels

29
Q

After ovulation, what is the role of the Corpus Luteum?

A

Forms spontaneously
Secretes Progesterone & Oestrogen
Maintains FSH suppression
LH suppressed by Progesterone inhibiting the positive feedback loop

30
Q

What occurs in the Luteal phase?

A

Corpus Luteum grows and secretes more steroids

31
Q

How many days is it until the Corpus Luteum dies if there is not a pregnancy?

A

14 days exactly.

Secretes prostaglandins and therefore cuts off its own blood supply so it dies

32
Q

If the woman is pregnant, what does the Corpus Luteum do?

A

It will continue to grow and secrete increasing amounts of steroids (Due to Human Chorionic Gonadotrophin from the developing placenta) and support the embryo

33
Q

What does death of the Corpus Luteum cause?

A

Rapid fall in steroid levels (Progesterone more quickly than Oestrogen)
Stimulates menses
Relieves inhibition of FSH

34
Q

What causes Menstrual bleeding in the Menstrual cycle?

A

The rapid decrease in Progesterone levels faster than Oestrogen causes Menstruation (Where necrotic tissue is cleared by blood)

35
Q

Where does variation in the length of the cycle come from?

A

Variation in timing of ovulation. The waiting/luteal phase is always 14 days and the preparatory phase is fixed too

36
Q

What is the pelvic clock?

A

The events of the ovarian cycle produce a timing signal

37
Q

When, in the Menstrual cycle, is Oestrogen high?

A

Begins low on day 0, increases slowly until it peaks just before the LH surge.
High for waiting phase then drops again

38
Q

When, in the Menstrual cycle, is Progesterone high?

A

Begins low then increased when ovulation occurs

Peaks in the waiting phase (Higher than oestrogen) then drops lower than oestrogen resulting in menstration

39
Q

What is the brain’s involvement in the female reproductive cycle/menstrual cycle?

A

Stimulates the gonad, but then a follicle develops and it takes over the brain

40
Q

How long does the Corpus Luteum support the embryo?

A

12-14 weeks then the placenta takes over

41
Q

Why are weeks 10 - 12 a very vulnerable time?

A

The support of the embryo is changing from the Corpus Luteum to the Placenta. This can cause spontaneous miscarriage as the embryo is very delicate

Reproductive system (16 decks)

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