Reproduction Lectures 2021 - FEMALE REPRODUCTIVE SYSTEM Flashcards
Female reproductive system is much more complex than male reproductive system - why?
not just gametogenesis; a lot more going on & a much greater energy investment
- fetal development, parturition and nursing
Two critical differences in gametogenesis:
– In females the number of available gametes is set at birth (conventional view)
– Female reproductive potential ceases in middle age (menopause)
- red. in estrogen is a result of the red. in repro. potential in females (pre & post menopause)
- males repro. potential is until the day they die
- but ADAMS can occur
ADAMS
the potential for producing motile & fertile sperm decreases as males age but there is still a potential that they may be able to reproduce as they age
Which 3 parts of the female reproductive system are embryologically derived from the SAME tissues in males as the penile head, penile shaft & scrotum?
- Clitoris - penile head
- Labium minora - penile shaft
- Labium majora - scrotum
During early dev. as an embryogenesis there is a phase known as a bipotential phase:
- where the developing embryo could go either way & develop as a female phenotype or a male phenotype
- the tissues that are involved in developing the male or female phenotype could go either way & are dependent on the expression on specific genes in that developing embryo
Fallopian tube
AKA oviduct
- connects to the ovaries
Ovary
- paired organs
- held to fallopian tubes by fimbriae
Uterus
- has 4 main aspects
- has 2 main linings
What are the 4 main aspects of the uterus?
- Uterine artery
- Outer connective tissue
- Myometrium
- Endometrium
Uterine artery
- imp. for providing energy & nutrients to the developing fetus if pregnancy occurs
- also imp. for removing those products in terms of the fetus side of things
Myometrium
- is smooth muscle
- interconnected - imp. during parturition in females
Endometrium
where the developing blastocyte will embed during early dev.
The connection b/t the ovary & the fallopian tube is not as tight & so occasionally, when eggs are ovulated, they are dropped & they don’t make it into the oviduct or fallopian tube & they will end up in the body cavity
- & then v. rarely you get:
ectopic pregnancy
Ectopic pregnancy
pregnancy occurs where it shouldn’t
- eggs can be fertilized in fallopian tube (can damage mother (can be fetal) or body cavity (v. rare - normally fetal in the absence of medical intervention)
Normal pregnancy should occur in the…
uterine cavity
Oogenesis
- All available gametes usually produced by the fifth month of gestation (cerca 6-7 million) – oogonia but only about 1 million PRIMARY OOCYTES survive at birth
- Meiotic division begins just before birth but is not completed – primary oocytes
- Maintained in a state of meiotic arrest (in prophase I) until puberty
By the time females reach puberty, how many primary oocytes do they have?
~300-400 000
Of those 300-400 000 primary oocytes at puberty, females on average will ovulate _______ in their lifetime…
~400 oocytes
Prophase I
arrested in 1st meiotic division
After puberty ____ primary oocyte is ovulated about once a month before menopause
1
What is ovulated?
23 (haploid) & polar body
All primary oocytes are surrounded by a single cell layer known as the…
zona pellucida
The primary follicle encompasses the…
primary oocyte a single layer of granulosa cells and thecal cells separated by a basement membrane
Thecal cells are v. important for…
steroidogenesis
Steroid synthesis is critical in both the…
granulosa & thecal cells
Basal lamina
separates the thecal & granulosa cells
Antral fluid
- not all follicles have this
- primary follicles don’t have this space
- only when they dev. into secondary/antral/graffian will the space become apparent
One of two fates for developing follicles:
1) Normal development - ovulation
- oocyte is ovulates
2) Degeneration - atresia
- without granulosa cells in the follicle, the follicle is unprotected & will rapidly degrade & be absorbed within the ovarian tissue
Astresia
degradation of the tissue
Research is ongoing to understand the endocrine mech’s asociated with determining which follicle gets “chosen” to be promoted toward ovulation. We know though that:
SIZE MATTERS & as follicles grow they become the dominant follicle & the smaller follicles regress & can assist in further dev. & aid in the dev. of the follicle that goes on to be ovulated
Ovarian cycle
• Three main components and it last ~28days
- The follicular phase
- Ovulation
- The luteal (postovulatory) phase
The follicular phase within the ovarian cycle
preparation of oocyte (& dev. of that follicle)
- dominated by presence of developing follicles
Ovulation within the ovarian cycle
release of (SECONDARY) oocyte - very short!
The luteal (postovulatory) phase
preparation of reproductive tract for pregnancy by hormones from the corpus luteum
Corpus luteum
where the follicular cells has differentiated into luteal cells
The expectation of the repro. system is that the…
ovulated oocyte will be fertilized & therefore will req. nurturing & appropriate environment for dev. & embryogenesis & ultimately fetal dev. & parturition of birth
- so the system has evolved to ready the repro. tract for that to happen & that is where the 3rd phase comes in (the luteal (postovulatory) phase within the ovarian cycle)
What is the ovarian cycle interrupted by?
- Pregnancy
- Menopause
- Nutritional balance, training (amenorrhea)
FSH & LH are governed by…
GnRH
The gonadotrophic hormones (FSH & LH) are produced by…
Hypothalamic Pituitary Gonadol (HPG axis)
So these pituitary hormones; FSH & LH will govern syn. & release of…
primarily estrogens in the 1st instance but also inhibins & progesterones later on in the cycle
- but estrogens are the main one that are driving this
As the follicle grows, estrogen levels ______
increase
The increase in estrogens within the circulation of females is a function of ___________
increasing follicular size
Uterine cycle AKA…
menstral cycle
Why do we begin at menses?
b/c menses is a v. obvious signal at the onset or start of this cycle (uterine cycle)
As the follicle grows we get the…
proliferative phase
Secretory phase
- predominant 1 during the luteal phase of the ovarian cycle
- secretion of the endometrial lining in anticipation of a fertilized oocyte being implanted in that endometrium lining
- if that doesn’t happen, then the cycle goes all the way back to the start
Core body temp of females will…
INCREASE just AFTER ovulation
Females trying to get pregnant will target this phase/period (just after ovulation) in their ovarian cycle as this is the period called oestrous where…
they make most likely to have success in getting pregnant
Oestrous
- a period of enhanced sexual receptivity
- in non-humans/mammals/primates this period is extremely on a signalling in many cases by females
- but also, the males have evolved to also be attracted to subtle signs & changes in females during that period of ovulation where the egg is most likely to be fertilized
Correlation b/t tip earnings & lap dancer menstrual cycle
Miller et al in 2007
- interested in groups of woman on oral contraception or cycling normally (not on oral contraception where they throw off the hormonal cycles that prevents pregnancy essentially)
- interested in their signalling b/t males & females using lap dancers & tips earned
- suggestion there was: if the individual was cycling normally, there would be more oestrous signalling produced by the lap dancer which might be more attractive to the male in partic. during that period of oestrous & indeed that is exactly the case
- suggests a period of oestrous did exist & were more attractive to the males - hence greater earnings
Uterine cycle
• Three main components and it last ~28days
- Menses
- Proliferative phase
- Secretory phase
Menses within the uterine cycle
beginning of the follicular phase
Proliferative phase within the uterine cycle
latter part of the follicular phase (additional endometrial lining laid down)
Secretory phase within the uterine cycle
After ovulation during the luteal phase
- prepares uterus for implantation if fertilization happens
Uterine cycle is interrupted by:
- Pregnancy
- Menopause
- Nutritional balance – training (amenorrhea)
*all true for ovarian cycle as well
Nutritional balance & training can be…
reversed & return to cycling normally & the same with training, it can return to normal cycling (take time but will return)
Amenorrhea
- lack of menstration in these individuals
- gymnasts & ballerina’s in partic. that were training intensively as younger females, in their early teens (maybe even prepubescent) & their menstrual cycle was abnormal & often didn’t exist
- reason for that: even though extrem. athletically fit, may lack the resources avail. for appro. cycling & ultimately if that egg is fertilized, the resources avail. to maintain pregnancy
- evolution sense
The primary oocyte is contained in the…
primary follicle
Zona pellucida
single cell layer
- will increase in width throughout dev. largely through the proliferation of granulosa cells & those cells directly dev. of the follicle
These 2 cell layers are directly developing. Where we have syn. of steroids & conversion of those steriods in further directing of dev.
theca & granulosa cell layer
Theca cell layer is analogous to ______ in males
leydig cells
Granulosa cell layer is analogous to ______ in males
sertoli cells
Basal lamina in females
- like the basal lamina within the seminiferous tubule in males
- analogous to the blood brain barrier
- layer of tissue that prevents immune system getting into this area (if it gets in it will probably attack the unknown cell type - oocyte - as it is unfamiliar to the immune system
Follicular development
- Theca & granulosa cells begin to synthesise and secrete ESTROGENS
- Follicle increases in diameter ~12-16mm (b/c of the synthesis)
• (as it grows, we get a:) Estrogen rich antrum
- & as it grows again, we get more & more estrogens that is produced - so the conc. of estrogens slowly & steadily rises as the cycle progresses
All estrogens are syn. & present within that….
antrum space
Estrone
Estradiol - highest concen.
Estriol
Ovulation itself is controlled by…
LH – main target thecal cells and FSH – main target granulosa cells
Just prior to ovulation…
first meiotic division completed (as the eggs are expelled into the oviduct)
Collagenases secreted by the follicle allows…
the mature follicle to break free (rupture)
The secondary oocyte is…
expelled into the abdominal cavity and quickly drawn into the oviduct (fallopian tube) (speaks to that ectopic pregnancy)
But, occasionally we will get 2 secondary oocytes expelled…
will lead to fraternal cells
- but if we get 1 egg that is expelled (same embryo divides twice) –> maternal twins (dizygotic twins)
Granulosa and thecal cells differentiate into…
corpus luteum
• Synthesise and secrete mostly progesterone with some estrogens
Why is the corpus luteum yellow?
b/c it’s full of LIPIDS
- lipids provide a precursor molecule for the steroids (a super steroid factory producing progesterones & estrogens)
The corpus luteum is fully functional within…
4 days & keeps going for another 5 days whether or not the egg is fertilized
If the egg is fertilized (fertilization) then…
the corpus luteum continues to grow (& continues to syn. steroids in support of the developing embryo within the uterus)
- develops into mature corpus luteum
If no fertilization occurs then…
we get degradation of the corpus luteum to the corpus albican (starts to rite? & will degrade & the cycle goes back to the start)
List the female sexual act phases:
- Excitement
- Plateau phase
- Orgasmic phase
- Resolution phase
- Excitement:
arousal and erection increase in PSNS and decrease in SNS
- CLITORIS is 1 tissue that will be engorged by blood & there is a # of nerve endings in the clitoris that are v. similar to the penile head
- Plateau phase:
continued arousal includes increased heart rate, mean arterial blood pressure, respiration rate and muscle tension
* - can also be increases in circulating levels of OXYTOCIN (can also happen in males)
What are the 2 possible effects from these increased levels of oxytocin?
- Oxytocin can promote pair bonding (b/t mother & child) & is v. relevant in young moms & suckling infants
- That during the sexual act, that increase in oxytocin can promote pair bonding b/t couples
- Another aspect of oxytocin is a promotion of transport of sperm within the female repro. tract (as the male will ejaculate into the female repro. tract - if there’s an increase in oxytocin, that promotes constriction of vascular smooth muscle
- promotes constriction of muscle that lines cervical canal & promotes constriction of the muscle that lines the endometrium/uterus & so will promote movement of sperm up through the female repro. tract
- & so potentially can promote the potential for fertilization
- Orgasmic phase:
unlike males this is not essential for successful fertilisation, however, it does aid in sperm transport.
- females can go through multiple orgasms
- there may be an increase in vasoactive hormone like oxytocin released into the female circulation, again further promoting movement of sperm through the female repro. tract & further enhancing the potential for fertilization of that egg
- Resolution phase:
if stimulation is sufficient arousal decreases but females do not have a period of latency as in males
