Female Menstrual Cycle & Sex Hormones (Luteal Phase)

3rd stage of this process

LH decreases over time until there is no longer enough to support courpus luteum

LH (Luthinizing Hormone)

Maintains the corpus luteum for the majority of this phase

What is the relationship between the follicle and the corpus luteum

Once ovulation occurs the follicle turns into the corpus luteum because egg bursts out of follicle and is now being stimulated by LH not FSH

Role of GnRH, FSH, and LH

To grow and develop the egg in order to release more estrogen and progesterone to maintain the endometrium

How do birth control pills work

Usually contain estrogen and progesterone and will prevent pregnancy because the provided hormones will prevent you from growing and developing an egg and ovulating, and the endometrium will not grow. Adding the hormones prevents ovulation.

What are the hormonal changes that cause ovulation and when do they occur during the menstrual cycle?

no LH, so corpus luteum degrades so there is no more estrogen and progesterone to maintain endometrium so its shed

What are the changes that occur in the uterus over the course of the menstrual cycle?

menstruation, regeneration of endometrium, endometrial development

CL (Corpus Luteum)

Contains lots of smooth ER, will release estrogen and progesterone which causes the endometrium to thicken and maintain in case of implantation

Luteal Phase

Days 15-28, starts at ovulation

2nd stage of this process

Estrogen and progresterone inhibit the hypothalamus and pituitary which means no release of GnRH, FSH, LH

What are the hormonal changes that cause ovulation and when do they occur during the menstrual cycle?

FSH stimulates follicle to grow and develop egg, follicle creates estrogen, estrogen stimulates they hypo to create more GnRH, causing the estrogen threshold to be reached and a surge of LH stimulating the follicle to release egg

What are the changes that occur in the ovary over the course of the menstrual cycle?

Follicle develops, ovulation, corpus luteum forms and matures, corpus luteum degenerates

How does the egg being fertilized prevent the endometrium from being shed

The embryo will release an LH mimic called HCG, meaning it can maintain itself despite the hypo an pit being shut off and endmetrium will not be shed

Hormonal Differences in a woman's body during a month in which she DOES become pregnant

The embryo, if egg is fertilized, will release an LH mimic called HCG meaning it can maintain itself despite the hypo and pit being turned off so endometrium is not shed. Estrogen and progesterone are still being released from embryo to maintain endometrium and placenta grows to protect fetus.

Hormonal Differences in a woman's body during a month in which she DOES NOT become pregnant

`Corpus luteum degrades if egg is not fertilized causing a decrease in LH over time, thus the levels of estrogen and progesterone will decrease --> neg. feedback loop

What happens in this phase?

egg takes 5-6 days to travel down fallopian tube, once ovulation occurs the follicle turns into the corpus luteum

1st stage of this phase

follicle turns into corpus luteum and positively stimulates estrogen and progesterone that will maintain nd grow the endometrium

Why is the luteal phase a negative feedback loop

in the luteal phase, the follicle is stimulated by LH to become the corpus luteum. The corpus luteum produces estrogen and progesterone. High levels of a combo of progesterone and estrogen cause a negative feedback loop which inhibits the hypothalamus from producing GnRH, therefore shutting off the production of LH and FSH. LH and FSH levels decline, therefore estrogen and progesterone levels drop as well. Menstruation occurs due to low levels of progesterone and estrogen when the egg is unfertilized and the corpus luteum dies. This loop occurs because you don't want to grow and ovulate another egg while one may potentially be fertilized.