Femeal Reproductive Physiology Flashcards
What are the two main phases of the female reductive system?
1) preparation of the female body for conception
2) maintain a pregnancy
Where do LH and FSH work on in the ovary
LH = theca cells
- function to promote follicular development development
FSH = granulosa cells
- function is to produce estrogen and progesterone
How does estradiol and progesterone affect GnRH release?
Estradiol
- promotes LH release
- inhibits FSH release
Inhibin A/B
- inhibit FSH release
Progesterone
- promotes FSH release
- inhibits LH release
What is included in the “vulva”
Labia majoria + minora
Mons pubis
Clitoris
Vestibule of the vagina
Vestibular bulbs
External urethral orifice
Homologous anatomical structures in women based on male counterparts
Labia majoria = scrotum
Clitoris = penis
Vagina structure and function
Is lined with nonkeritinized stratified squamous epithelium
- also possesses a thick lamina propria layer with enriched elastic fibers
Does not lubricate its self instead gets from
- cervical mucus
- transudate from blood vessels of the lamina propria
- secretions from greater vestibular gland
Vaginal wall has three layers
1) mucosa
2) Muscularis
3) adventitia
The vagina is innervated by the pudendal nerve
Is affected by three primary hormones
1) estrogen = stimulates proliferation of vaginal epithelium
2) estradiol = induces minimal keratinization of the apical layers
3) progesterone = increases desquamation of the epithelial cells
- *glycogen metabolism in the vagina causes lactic acid build up by commensal lactobacillus
- this reduces infections of bacteria and fungi**
Cervix structure and function
Inferior extension of the uterus that projects into vagina
acts as the gateway into the upper female tract
- during mid cycle (ovulation) = facilitates sperm viability and entry into the Fallopian tubes
- during the luteal phase = serve to impede the passage of sperm and microbes (lowers chance of superimplantation of second embryo and infections
DOESNT undergo menstration changes and can physical support the baby’s weight during pregnancy
Hormonal regulation of the cervical mucosa during menstral cycle
Estrogen = stimulates production of copious quantities of thin and watery slightly alkaline mucus
- ideal environment for sperm
Progesterone = produces viscous acidic mucus that is hostile to sperm
- is hostile to sperm and forms a barrier within the endocervical can also during secretory phase of the endometrium and pregnancy
Uterus anatomy
Single organ that sits in the midline of the pelvis between rectum and bladder
Has 4 parts
- fundus = superior portion that rises superiorly from the entrance of the oviducts
- the body = most of the uterus and site of embryoblast implantation
- the isthmus = narrowed part of the body connecting the Fallopian tubes on each side
- cervix = most inferior portion
Functions to
1) provide a suitable site for attachment and implantation for the blastocyst with a nutrient rich stroma
2) limit the invasiveness of the implanting embryo so it stays in the endometrium
3) provide a maternal side of the mature placental architecture
4) grow and expand with the growing fetus
5) provide strong muscular contractions that expel the fetus at birth
Structure of the uterine endometrium
Endometrium = mucosa of the uterus
2/3rds of the luminal side of the endometrium is lost during menstration
- this is called the functional zone or “stratum functionalis”
- is fed by spiral arteries
1/3rd of the luminal side remains tonic even during menstration
- this is called the basal zone or “stratum basale”
- is fed by straight arteries
- contains all cell types of cells of the endometrium
Endometrial cycle
is controlled primarily by estradiol and progesterone primarily and is a cyclic monthly growth and breakdown
3 primary phases
1) proliferative phase = 1-11th days
2) secretory phase = 12-24th days
3) menstrial phase = 25-29th days
after menstruation, the endometrium is restored within 5 days
- this is stimulated by estrogen from developing follicles
- however estradiol primary does the proliferation since it stimulates (IGF, TGF, EG) factors by endometrial cells which work in paracrine fashion to induce maturation and growth of the endometrium
Progesterone. Opposes estradiol during the luteal phase by up regulating 17B-HSD enzymes. These enzymes convert estradiol -> estrone which is a weaker estrogen. Also decreases ER levels in endometrial cells
- all of progesterone effects halt the proliferative phase of the endometrial cycle
If the oocyte is not fertilized within 14 days of ovulation, a sudden drastic drop in estradiol and progesterone will occur and cause demise of the corpus luteum
- the functional layer of the endometrium begins to atrophy and break down (signaling the start of the 1st day of the menstrual cycle/phase)
Ovulation/ovarian cycle
Occurs in tandum with endometrial cycle
Contains 4 main events
1) folliculogenesis
2) ovulation
3) formation of the corpus luteum
4) atresia/death of the corpus luteum
3 phases
1) follicular phase
- days 0-14 and aligns with proliferative phase (which is proliferation for he functional layer of the endometrium)
- the follicle develops in the ovaries as well and releases estrogen tonically which helps endometrial growth
2) ovulation phase
- roughly day 15 and is in between secretory and Proliferative phases
- begins when the follicle is mature and ruptures releasing an ovum
3) luteal phase
- roughly day 15/16 - 28 and lines up with secretory phase
- begins with transformation fo the follicular cells into a corpus luteum and further proliferates the endometrium
- if fertilization doesnt occur, then menstral cycle occurs roughly 18 days in for 3-5 days.
What causes the sudden rise in Basal Body Temperature (BBT)
During every ovulation cycle the body the increases in internal temperature in 0.3-0.5C
- this is due to progesterone release by the corpus luteum
can be seen iatrogenic if injecting progesterone and progestogen
Fallopian tubes (oviducts)
Muscular tubes at each end of the uterus with a “infundibulum” at the ends of both tubes
- infundibulum = contains cillia that helps move oocyte towards the uterus
- also contains “peg cells” which help nourish and support ovum, sperm and zygote if fertilization occurs in the tubes
3 main functions
1) capture the oocyte-cumulus complex at ovulation and transport it to the uterus
2) provide a site for sperm storage (can stay there for 5 days)
3) providing nutritional support to the preimplantation embryo by its secretions
- *is promoted/proliferates in response to estrogen**
- increases blood flow to the lamina propria of the oviducts and concentration of glucose proteins
- increases secretion of thick mucus in the isthmus
- also increases tone of the isthmus to keep oocyte complex there for fertilization
if exposed to high progesterone though, decreases cell sizes and function of the oviducts
When does the blastocysts typically implant in the uterus?
Around day 5 or 6
Ovary
Made up on ovarian follicles which are functional units
Functions:
1) produce haploid gametes
2) facilltates syngamy/fertilization
3) supply’s a site for embryo EM plantation
4) provide physical environment and nutrient needs of the developing fetus
5) nurture neonate
Follicle life cycle
Primary follicle
- presence of zona pelludica begins
- single layer of granulosa cells also form
Secondary follicle
- theca cells begins o form
- 3-6 layers of granulosa cells
(Growing Antrial) Early tertiary follicle
- can Antrim of the follicle starts to develop
- two layers of theca cells form (inner layer = secretory cells and small blood vessels; outer layer = CT, smooth muscle and large blood vessels)
Corona radiata forms also
Dominant follicle
- rapid growth occurs and meiosis resumes to form the secondary oocyte + a polar body
- actually oocyte forms
- everything increases in size as well
Ruptured follicle
- releases ovulated oocyte
- before corpus luteum develops, LH is produced by the granulosa cell to both further induce endometrium growth and also transformation for he ruptured follicle into corpus luteum
Corpus luteum
- the entire follicle is converted into luteal cells which
- begins Secretion of progesterone which inhibts LH effects
- *once progesterone levels increase = ovulation has occurred**
Regression corpus luteum
- corpus luteum degenerates and this begins the menstration phase
- forms corpus albicans
How many primordial follicles are present at menarche
Roughly 300,000
- 30,000 go to growth
- less than 500 become dominant follicles (these stay and 1 is released each month)
270,000 roughly undergo atresia
Oogenesis cycle
Primary oocyte are formed at birth and arrest in prophase 1 until puberty hits
At puberty = meiosis resumes and forms mature secondary oocyte each month which then arrests into metaphase 2 until fertilized (then just keeps going in mitosis to form the neonate)
Result of full meiosis = 1 secondary oocyte and 2 polar bodies
Ovarian hormones
1) estradiol
- MOST abundant and potent ovarian form of estrogen
- is produced by the granulosa cells
2) estriol/estrone
- less potent estrogen produced by the liver during pregnancy
- estrone = liver; estriol = from estrone
- is formed in post menopausal women in peripheral tissues from chronic conversion of estradiol
3) progesterone
- synthesized by follicular and luteal cells
- function is to suppres estradiol
4) dehydroepiandrosterone and androstenedione are formed by theca interna cells
- are essentially weak progesterone
5) relaxin = relaxes pelvic ligaments and softens cervix for child birth
- released by ovary and placenta
6) inhibin = inhibits LH release
What determines the reproductive life span of a women?
The rate at which resting premedical follicles die off
- this number is a fixed and finite number during puberty
Theca and granulosa cell functions broadly
Theca cells
- found in natural follicles
- take cholesterol and produce large amounts of androstenedione and testosterone which go to granuloma cells to be converted into estradiol (this is because granulosa cells cant synthesize androstenedione by themselves)
- are directly regulated by LH levels
- possess high levels of CYP17 and 17-hydroxylase activity
Granulosa cells
- androgens are converted to estradiol-17B and some estrone
- also directly is induced by FSH to induce proliferation and more expression of CYP-19 aromatase enzymes (estrogen synthesis)
- **in early follicular phase, will release inhibin B which exerts negative feedback on FSH secretion
Two cell-gonadotropin model
1) during follicular phase
- follicle secretes estradiol
- LH primes theca cells to convert cholesterol into androstenedione which is then shipped to granulosa cells to be converted into estradiol by aromatase enzymes (granulosa cells dont have aromatase enzymes)
- granulosa cells however dont have the ability to produce androstenedione by themselves so they need theca cells to produce it and release in paracrine fashion
- this all promotes ovulation cycle
2) during the luteal phase
- vasculization of corpus luteum makes LDL available to granulosa and theca cells in corpus luteum
- this means the corpus luteum is producing mass amounts of progesterone which starts inhbit estradiol release and begins menstrational cycle
Ovarian steroids in menopause
Shows an abrupt increase in constant GnRH and FSH/LH
- however at this time, the number of primordial follicles to secrete estrogen is diminished, so there is no negative feedback on FSH/LH which results in these mass increases
this continuous secretion however also tonically reduces ovulation
Once the primordial follicles hit zero = no estrogen = complete cessation of ovulation
Levels of sex hormones during the entire ovarian and endometrial cycle
Follicular phase/proliferative phase
- LH and FSH are highest
- estradiol starts to slowly increase as well and peaks right before ovulation
- inhibin and progesterone levels remain low/ irrelevant
- *at ovulation = massive LH spike with a mild FSH spike (signal for ovulation)**
Luteal phase/Secretory phase
- Progedsterone is the highest hormone
- estrodiol is elevated but not as high as progesterone
- FSH/LH falls And inhibin rises
Estrogens vs androgen effects on secondary sex characteristics
Estrogen = controls breast development and fat distribution
Androgens (progesterone, testosterone) = control pubic and axillary hair growth and libido
Distribution of gonadal steroids and cortisol in plasma
Testosterone:
2% = free
65% = GBG protein
33% = albumin bound
Androstenedione
7% is free
85% is albumin bound
8% is GBG bound
Estradiol
2% is free
60% is albumin bound
38% is GBG bound
Progesterone
2% is free
80% is albumin bound
18% CBG bound
Cortisol
4% is free
90% is CBG bound
6% is albumin bound
What is the primary puberty defining endocrine event in both males and females
The invitation of pulsatile secretion of GnRH
What is the female athlete triad? (FAT)
Oligo /amenorrhea
Eating disorders/extensive dieting
Decreased bone density/osteopenia
- *low body mass index results in altered hypothalamic functions and causes decreased pulsatile secretion of GnRH -> FSH/LH**
- this in turn decreases estrogen and progesterone
Estrogen is even further decreased to weight loss/low adipocytes since adipocytes are known for slight peripheral conversion of testosterone -> estradiol and also release leptin which (on top of doing its primary function of controlling satiety) also promotes GnRH release
Main differences between male and female reproductive systems
1) gonad placement
- males = outside abdominal cavity in scrotum. Are also continuous with reproductive tract
- females = abdominal cavity. Are not continuous with reproductive tract
2) gamete production
- males = are replenished throughout life and release is continuous
- females = have a set amount at puberty and release one every 1 month. Exhaustion = menopause
3) reproductive tract actions
- males = no rhythm or time frame and functions only for male gamete transport
- females = has a cycle/rhythm and functions for male and female gamete transport
4) primary androgen present
- males = always testosterone
- female = estrogen during 1st half of monthly cycle, progesterone = 2nd half
