Chapter 8: Follicular Phase

Lecture 11

In the estrous cycle, day 0 corresponds to \_____ and ovulation occurs \_____

Estrus, during estrus

In the menstrual cycle, day 0 corresponds to \_____

Menses

In the menstrual cycle, days 0-14 corresponds to which phase?

Follicular phase

In the menstrual cycle, days 14-28 corresponds to which phase?

Luteal phase

In the menstrual cycle, the thickness of the endometrium in the follicular phase is \_______.

Proliferative

In the mentrual cycle, the thickness of the endometrium in the luteal phase is \______.

Secretory

In the menstrual cycle, the follicular phase is driven by what hormone?

Estradiol

In the menstrual cycle, the luteal phase is driven by what hormone?

Progesterone

Estrous cycle: length of follicular phase

20% or less of the cycle

Menstrual cycle: length of follicular phase

50% of cycle

Estrous cycle: time of ovulation

At the beginning and end of each cycle

Menstrual cycle: time of ovulation

Middle of the cycle (day 14)

Estrous cycle: length of luteal phase

80% of the cycle

Menstrual cycle: length of luteal phase

50% of the cycle

Estrous cycle: length of fertile window

24 hours or less (5% of the cycle)

Menstrual cycle: length of fertile window

Up to 6 days before ovulation (18% of the cycle)

Only the \______ cycle has sloughing of the endometrium

Menstrual

Estrous cycle: sexual receptivity

Well defined

Menstrual cycle: sexual receptivity

Uniform throughout cycle

Progesterone function in both the estrous and menstrual cycle

Inhibits GnRH

Does progesterone impact sexual receptivity in the estrous cycle?

Yes, inhibits sexual receptivity

Menstrual cycle: menopause

Well charactarized (follicular depletion)

What is the anti-pathogen hypothesis?

The idea that menstruation serves as a mechanism of removing sperm-borne pathogens and prevents infection

Why is the anti-pathogen hypothesis flawed?

Blood is a great medium for growin infectious organisms
Is an inefficient means of infection control because bleeding happens every 28 days
Pregnant, lactating, and post menopasual women are unprotected

What is the conservation of energy hypothesis?

Cyclical regression and renewal is less energetically costly than maintaining the active state necessary for pregnancy all the time

Why is the conservation of energy hypothesis flawed?

The amount of energy saved by regression and regeneration of the endometrium is relativly very small

What is the coevolution of the embryo and endometrium hypothesis?

Menstruation is a result of an immune response to the embryo, which is haploid

In egg laying animals, what protects the embryo from an immune response?

The egg casing

In viviparous animals, what protects the embryo from an immune response?

P4 controlling the inflammatory reaction

According to Elsimar Coutinho, why is menstruation "unnatural"?

Ancient women were continuously pregnant/lactating, and therefore not menstruating

What was the average number of ovulations per woman in the past?

160

What is the average number of ovulations per woman now?

450

What is Seasonale and how does it work?

Extended birth control pill and menstruation suppression, 84 active pills and 7 placebo. It works by using synthetic steriods to decrease ovulatoin and endometrial growth

What are some benefits of menstruation suppression?

Relief from menstrual pain, convenience, less blood loss, less risk of anemia, possibly decreased chance of ovarian cancer

What are some risks of menstruation suppression?

Short term: blood clots, stroke, heart attack
Long term: unknown, decreased fertility or effects on other organs

What marks the beginning and end of the follicular phase?

Beginning- corpus lutem regression
End- ovulation

What are the two stages in the follicular phase?

Proestrus (follicular development) and estrus (sexual resceptivity)

What are the 4 major events during the follicular phase?

1. increased gonadotropin released
2. follicular growth
3. sexual receptivity
4. ovulation

What hormone is part of the negative feedback loop on GnRH in the surge and tonic center?

P4

What hormone is part of the negative feedback loop on FSH?

E2 and inhibin

What hormone is part of the positive feedback loop on GnRH in the surge center?

E2

The tonic center releases what type of secretions of GnRH?

Basal (episodic)

What type of release of GnRH is the surge center responsible for?

Preovulatory release of GnRH

What activates the surge center to release GnRH?

Threshold level of E2 during low P4

What activates the tonic center to release GnRH?

Nothing, it is spontaneous (pulse generator)

Without E2, what type of GnRH release does the surge center have?

Basal secretion of GnRH

What does basal secretion of GnRH cause in the pituitary-ovary axis?

FSH and LH release, which causes follicular growth

What does preovulatory release of GnRH cause in the pituitary-ovary axis?

LH surge, which triggers ovulation

What does follicular growth cause?

Increased levels of E2, which stimulates GnRH release

What occurs to hormones after ovulation?

P4 increase and E2 decrease, which suppresses GnRH release

What types of feedback systems can E2 cause?

Both negative or positive feedback

What types of feedback systems can P4 cause?

Only negative feedback

How does low E2 and high P4 affect gonadotropin release?

Decreased GnRH in the tonic center, decreaesd FSH and LH in the anterior pituitary, less E2 from the follicle

How does high E2 and low P4 affect gonadotropin release?

Increased GnRH from the surge center, increased FSH and LH from the anterior pituitary, increased E2 from the follicle

What typically ends a positive feedback loop?

A structural event

What is the structural event that ends the E2 positive feedback loop?

Ovulation

What are the 4 processes of folliuclar dynamics?

Recruitment, selection, dominance, atresia (degeneration)

What do antral follicules develop in response to?

Tonic levels of FSH and LH

What is follicular dynamics?

process of follicular growth and degeneration

What is a monotocous species?

A single bearing offspring speices where a single follicle proceeds towards dominance

What are examples of a monotocous species?

Cattle, mare, women

What is a polytocous species?

Litter bearing offspring where multiple follicles proceed towards dominance

What are examples of a polytocous species?

Pigs, dogs, cats

In the recruitment phase, what hormones are present?

FSH (in higher amounts than LH) and NO inhibin

During the recruitment phase of follicular dynamics, what develops?

Small antral follicles with the production of E2

In the selection phase of follicular dynamics, what is growing?

Medium (selected) antral follicles with more E2 production

What hormones are present during the selection phase of follicular dynamics?

FSH and LH in similar amounts, low levels of inhibin

In the dominance phase of follicular dynamics, what is determined?

The dominant (preovulatory) follicle(s) with high E2 levels

What hormones are present during the dominance phase of follicular dynamics?

LH (in higher levels than FSH) and high levels of inhibin

\___________ \__________ occurs at all stages of follicular development

Follicular degeneration

More than what percentage of follicles undergo atresia?

90%

What induces atresia of dominant follicles in the first follicular wave?

High levels of progesterone

During what phase of the estrous cycle does the first follicular wave begin and end?

Begins at the start of metestrus, ends middle of diestrus

During what phase of the estrous cycle does the second follicular wave begin and end?

Begins in the middle of diestrus, ends during estrus

What parts of follicular dynamics depend of FSH?

Recruitment and part of selection

What parts of follicular dynamics depend of LH?

Selection, dominance, and dominant prevoulatory

What do theca interna cells produce?

LHr and testosterone

What do granulosa cells produce?

FSHr and E2

What hormone combo results in female sexual receptivity?

Elevated E2 and low P4

What are some effects of estrogen?

Genital swelling, leukocytosis, increased genital secretion, uterine gland growth, elevated myometral tone