Periods 101 Flashcards
The hypothalamus pituitary ovarian axis releases hormones…
GnRH is secreted by the hypothalamus which stimulates cells anterior pituitary to make FSH and LH which act on the ovaries.
Menstrual cycle is a …
Menstrual cycle is a reflection of cyclic release of hormones on the hypothalamic-pituitary-ovarian axis (HPO axis).
GnRH stands for
Gonadotropin releasing hormone is secreted in pulses by the hypothalamus and starts the menstrual cycle.
FSH stands for …
Follicle stimulating hormone
FSH stimulates follicles so that they grow and produce estrogen.
Link: FSH, follicles, estrogen
LH stands for …
Luteinizing hormone, promotes ovulation
Link: ovulation
Menstrual cycle consists of ..
The ovarian and uterine cycle, which each have three phases.
Ovarian cycle, three phases …
Follicular phase
Ovulatory phase
Luteal phase
Uterine phases …
Proliferation phase
Secretory phase
Menstrual phase
Ovarian cycle, follicular phase, details …
Follicular phase
- starts on day 1, start of menses, and ends just before ovulation
- 10 - 17 days (variable), most variable phase
- estrogen rises during days 1-5
- mid-follicular phase … Competition to become dominant follicle
Follicles are …
Follicles are little fluid filled sacks with an immature egg in the middle. About 1 million follicles exist at time of birth, many are absorbed during childhood. By puberty about 400,000 left that are eligible to develop into eggs.
During the first half of the follicular phase, 10 to 20 follicles are recruited to start growing. These follicles are estrogen factories. The 10 - 20 recruited follicles compete against one another to become the dominant follicle.
Dominant follicle selection happens on day 7.
Recruited follicles are …
Estrogen factories
Follicular phase, estrogen …
From day 1 to 7, estrogen levels increase but remain moderate which inhibits the secretion of FSH and LH by the anterior pituitary. This is a classic negative feedback loop.
Day 7, the dominant follicle is established, the other follicles break down through a process called atresia.
Day 7 to the end of the follicular phase, the dominant follicle continues to mature and produce high levels of estrogen. The high levels of estrogen stimulates FSH and LH in the classic positive feedback loop leading to the ovulation-inducing LH surge.
At the end of the follicular phase, the mature follicle bulges on the surface of the ovary …
Ovarian cycle, ovulatory phase
Ovulatory phase:
- LH surge, then … 32-34 hours post surge start, 10-12 hours post peak
- Follicle protrusion, vesicles rupture, oocyte expulsion
- Ovulation
Ovarian cycle, Luteal Phase
Luteal phase …
- begins with ovulation and ends with menses
- last 14 days, with little variety, highly reliable
- post ovulation, walls of follicle collapse,
- dominant follicle becomes corpus luteum (CL) “yellow body”
Ovarian cycle, Luteal phase and ____ hormone …
Luteal phase:
- the corpus luteum (CL) produces large amounts of progesterone.
- this progesterone suppresses the growth of new follicles
- progesterone causes an elevation in basal body temperature
- if no conception, 9-11 days post ovulation, CL regresses rapidly
- CL regression results in decreasing progesterone levels
- withdrawal of hormones … Menstruation