Repro Physl 6 Flashcards
Which cells does FSH act on?
Granulosa cells
What receptors do Granulosa cells have?
FSH receptors
When do Granulosa cells gain LH receptors?
With development and increased proliferation of granulosa cells
What cells does LH act on?
Theca cells
What receptors do Theca cells have?
LH receptors
How does FSH affect granulosa cells?
It will support the proliferation of granulosa cells and their function in converting androgen to estrogen and producing secretions
Aside from FSH what supports further proliferation of Granulosa cells?
Estrogen produced by the granulosa cells themselves (positive feedback)
What do increased levels of estrogen in the follicle do?
Increase the expression of FSH and lead to expression of estrogen receptors on granulosa cells for positive feedback. So they respond to FSH and estrogen
What do theca cells synthesize in response to LH?
Androgens
How do the androgens released by theca cells affect granulosa cells?
The androgens can diffuse to granulosa cells and produce estrogen with them
What are the granulosa cells similar to in the testis and why?
Sertoli cells because they sustain and provide nutrients to the developing germ cells and respond to FSH and gonadal sex hormone
What are the Theca cells similar to in the testis and why?
Leydig cells because in response to LH they produce androgens that diffuse across to the other cells
Why do non-dominant follicles degenerate?
Because of a drop in FSH
What suppresses the FSH being released in the follicular stage?
The rising estrogen being produced by the follicle
What kind of receptors will the dominant follicle have and why?
Increased FSH receptors so that it can still be stimulated even though the FSH hormone is decreasing to cause the degeneration of the other follicles
What is the dominant follicle receptive to?
Both FSH and LH
Why are there rising levels of LH in the follicular phase?
Due to positive feedback by high levels of estrogen by the dominant follicle
What does stimulation of granulosa cells by FSH and LH in the follicular phase do?
Helps to sustain local increases in estrogen within the follicle
What negative feedback does estrogen exert in the follicular phase?
A negative feedback inhibition of gonadotropin secretion
Why can estrogen be produced by granulosa cells?
Through conversion of androgen to estrogen
Where does the estrogen from granulosa cells in the follicular phase go?
Into the circulation and locally in the ovaries
What does estrogen produced by granulosa cells in the follicular phase in the blood do?
In low to moderate levels it exerts a negative feedback effect of gonadotropin release and hypothalamic GnRH release
What exerts negative feedback on the gonadotropin release on the anterior pituitary and hypothalamus?
Estrogen produced by granulosa cells and inhibin produced by granulosa cells
What does inhibin produced by granulosa cells have an effect on?
It inhibits the release of FSH
When does the estrogen peak occur?
In the late follicular phase when the dominant follicle is producing a lot of estrogen
When does estrogen no longer have a negative feedback effect in the follicular phase?
When at the end of the follicular phase the dominant follicle is producing a lot of estrogen
What does the large amount of estrogen produced by the dominant follicle at the end of the follicular phase do?
Support secretion of LH from the anterior pituitary which supports development of the LH surge. And it also increases GnRH production from the hypothalamus
What is absolutely required for ovulation?
The LH surge that occurs due to positive feedback from the dominant follicle producing estrogen
What stimulates ovulation to occur?
High levels of LH
What does the corpus luteum produce?
Estrogen and progesterone
Where are kisspeptin neurons found?
Upstream of GnRH neurons in the hypothalamus
What is the beginning of the Luteal phase marked by?
Ovulation
What happens to LH after ovulation?
There is a decrease in LH levels
What does the drop in LH levels of the luteal phase do?
Stimulates the transformation of granulosa and theca cells in the follicle into the corpus luteum
What does the corpus luteum mainly prouce?
Progesterone, estrogen and inhibin
What does the combination of progesterone, estrogen and inhibin produced by the corpus luteum do?
It suppresses anterior pituitary gonadotropin release (FSH and LH)
Where does inhibin specifically have a negative feedback on?
FSH in the anterior pituitary
What does the progesterone and estrogen produced by the corpus luteum have a negative feedback effect on?
Hypothalamic GnRH production which shuts down the cascade
Why does the corpus luteum produce estrogen, progesterone, and inhibin?
To decrease levels of FSH and LH so that there is no production of another follicle to produce a mature ovum
What phases in the uterus correspond to the follicular phase?
The menstrual and proliferative phase
What phases in the uterus correspond to the Luteal phase?
Secretory phase
What happens to the endometrium during the menstrual phase?
There is a degeneration of the endometrium
Why does the endometrium begin to thicken after menstruation in the proliferative phase?
In response to estrogen produced by the granulosa cells in the developing follicle
How long is the proliferative phase?
About 10 days
What is the proliferative phase?
The period of time at the cessation of menstruation and until the time of ovulation that is stimulated by increase endometrium growth by estrogen from the granulosa cells of the developing follicle
What happens to the endometrium after ovulation?
It will begin to produce glycogen under the influence of progesterone and estrogen from the corpus luteum
Why does the endometrium produce glycogen after ovulation?
To be an energy store for implantation
What is the secretory phase?
The period in the endometrium where it is secreting glycogen and glycoproteins under the stimulation of estrogen and progesterone from the corpus luteum for the potential ovum
What receptors are produced in the uterus during the proliferative phase?
Progesterone receptors
What does the increase in progesterone receptors from the proliferative phase do in the post-ovulation/secretory phase?
It allows for progesterone to act on the endometrium and converts it to a secretory tissue
What is the response of the endometrium due to progesterone?
- Increases glands coiled and glycogen filled
- Increased vascularization
- Enzymes accumulate glands and connective tissue
How does progesterone affects the myometrium?
It inhibits myometrial contractions
How do estrogen and prostaglandins affect uterine muscle?
They stimulate the contraction of uterine muscle
Why does progesterone inhibit the contraction of uterine muscle?
To maintain a stable uterine environment for implantation
What happens if there are not sufficient levels of progesterone during pregnancy?
Then premature delivery can occur
How does estrogen (leading up to ovulation) affect the cervix?
- Abundant watery, clear mucus
* Important for facilitating sperm movement into the uterus
How does progesterone (after ovulation) affect the cervix?
- Thick sticky consistency of mucus
- Yellowish white
- Forms a plug
What happens to the corpus luteum if there is no fertilization of the ovum?
The corpus luteum degenerates (involudes)
What happens to the endocrine function of the corpus luteum after it degenerates?
It no longer has an endocrine function so estrogen and progesterone will plummet
What triggers menstruation?
The degeneration of the corpus luteum that produced estrogen and progesterone
What is the first step in menstruation?
The constriction of uterine blood vessels
Why is there a constriction of uterine blood vessels?
To deprive the cells of oxygen and nutrients
What is the constriction of blood vessels in menstruation mediated by?
Prostaglandins
What is the increase in prostaglandins causes by?
Decrease circulating estrogen and progesterone
What is the remaining thin base layer important for after menstruation?
For regeneration of the endometrium after each cycle
What does the dilation of blood vessels in the endometrium do?
It causes hemorrhage through capillary walls to allow endometrial tissue and debris to exit the vagina
Where does estrogen typically have its effects?
Locally or anywhere estrogen has its receptors
What is estrogen important for in the uterus?
For increasing the proliferation of the endometrium and expression of progesterone receptors on endometrial cells
What increases responsiveness of tissues to progesterone?
Estrogen increasing progesterone receptors in other tissues. This is known as estrogen priming
When is the peak production of progesterone?
After ovulation
What effects does progesterone have on estrogen?
It has anti-estrogen effects by limiting the expression of estrogen receptors
What do the low levels of estrogen do even before puberty?
They have a negative feedback effect on GnRH release and gonadotropin release
What is Leptin produced by?
Adipose cells in the body
What is one function of leptin on the hypothalamus?
Stimulates GnRH production
What is Amenorrhea?
Failure to have a menstrual flow?
What is Primary Amenorrhea?
The failure to begin normal menstruation cycles at puberty
What can cause Primary Amenorrhea?
Anorexia nervosa, less body fat
What is Secondary Amenorrhea?
Loss of previous normal menstrual cycles
What is can cause secondary Amenorrhea
- Pregnancy, menopause
* Anorexia nervosa
