7 - Menstrual Cycle Flashcards
What are the two cycles that make up the menstraul cycle and what is the length of a normal cycle?
- Ovarian Cycle: provide environment for oogenesis in ovary
- Uterine Cycle: prepare uterus to recieve fertilised oocyte
21-35 days
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What is the difference in the negative feedback system on the HPG between males and females?
- Testosterone has inhibitory affect on hypothalamus and anterior pituitary
- Oestrogen can be positive or negative feedback depending on where in the cycle
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Why is GnRH being released in a pulsatile manner important in the reproductive system?
If there was a continous production it’s receptors in the pituitary would become desensitised so may lead to infertility
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What is endometriosis and how can it be treated?
What?
- Ectopic endometrial tissue leading to abdominal pain
Treatment?
- Give continuous GnRH to stop desensitise receptors
- OC pill
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/677/a_image_thumb.png?1571659473)
How can you treat precocious puberty?
Give constant GnRH to densensitise receptors
What is the role of FSH and LH in females?
FSH: allows folicles to develop in ovary at start of cycle. follicles produce oestrogen and inhibin (which is negative feedback on FSH)
LH: LH surge drives ovulation
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What is the first stage of the menstrual cycle?
Follicular phase
- No inhibition from steroids or inhibin so FSH levels rise
- Number of granulosa cells increase due to FSH and causes development of theca interna/externa
- Follicle produces oestrogen so oestrogen levels rise and exert negative feedback on anterior pituitary
- Follicles form into Graafian follicle and oestrogen levels rise further exerting positive feeback on HPG
- Inhibin levels rise stopping FSH so only LH rise
- This stage is variable
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What are the different stages of follicular development in the ovary?
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When is the dominant follicle chosen in the follicular cycle and how is it chosen?
- Around 7th day
- Decrease in FSH due to the inhibin secretion
- Increase in LH due to the rising oestrogen having positive feedback
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/702/a_image_thumb.jpeg?1571660195)
What causes ovulation - the release of the mature follicle?
- Inhibin and oestrogen rise rapidly and no longer dependent on FSH
- Progesterone production begins and granulosa cells responsive to LH, modulating GnRH pulse generator
- LH surge
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/709/a_image_thumb.jpeg?1571660691)
What happens to the oocyte during ovulation?
- Meiosis I completes and II starts
- Oocyte extruded through the capsule
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/720/a_image_thumb.png?1571683214)
What happens to the levels of sex hormones immediately after ovulation?
- Follicle luteinised and starts to secrete oestrogen and progesterone in large quantities
- Inhibin continued to be produced
- LH suppressed due to negative feedback of progesterone
- Waiting phase where gamete development suspended
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/727/a_image_thumb.png?1571683586)
What is the second stage of the ovarian cycle called?
- Luteal Phase
- Corpus Luteum has absolute lifespan of 14 days
- Oestrogen, progesterone and inhibin all secreted from theca and granulosa
- If LH stays high corpus luteum regresses
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/733/a_image_thumb.png?1571683786)
What are the two stages of the uterine cycle?
- Proliferative phase
- Secretory phase
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/326/741/a_image_thumb.png?1571683894)
What occurs in the proliferative phase of the uterine cycle?
- Endometrium thickens in response to oestrogen from the ovary
- Simple straight glands that start to become coiled glands as the functional layer doubles
- All occurs at start of cycle
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