Reproduction - Lecture 24 Flashcards
what are the 3 sets of structures of sex organs?
- GONADS (tissue/organ):
- testes for males, ovaries for females
- contain germ cells (ova and sperm) (half of chromosomes)
- produce gametes and sex hormones - INTERNAL GENITALIA
- accessory glands and ducts
- Wolffian ducts, Mullerian ducts - EXTERNAL GENITALIA
- external reproductive structures (vagina, penis)
- genital tubercle, urethral folds, urethral groove and labioscrotal swellings
Nucleated cells contain _____ chromosomes –> haploid or diploid?
- ____ pair(s) of homologous autosomes
- ____ pair(s) of sex chromosomes: ___ and ____
- eggs and sperms are haploid or diploid? –> ____ autosomes and ___ sex chromosome
- 46 chromosomes –> diploid
- 22 pairs homologous autosomes (44)
- 1 pair of sex chromosomes: XY or XX
- eggs/sperms: haploid –> 22 autosomes and 1 sex chromosome
how to determine genetic sex?
- female vs male?
- Turner syndrome?
sex chromosomes determine genetic sex –> more specifically, sperm determines sex of zygote
- XX = female –> will have X chromosome inactivation: mechanisms to regulate the fact that 2 X chromosomes –> some cells have maternal X inactivated, vs others have paternal X inactivated
- XY = male –> Y is essential for development of mal reproductive organs
- Turner syndrome = only 1 X –> might have infertility
What is the basis of sex differentiation?
- 4 steps for male development
gonads have bipotential –> 2 structures in tissue
1. if Y chromosome = activation of SRY
2. expression of SRY gene will develop male gonads –> SRY stimulates TDF, SOX9
3. SOX9 stimulates sertoli cells to produce AMH –> so only Wolffian ducts are developed + regression of mullerian ducts
4. SRY also stimulates interstitial cells that secrete testosterone –> develop Wolffian duct into accessory structures + develop male external genitalia
describe male embryonic development
- using which genes?
- which ducts develop into what (3) induced by what?
- which ducts degenerate? induced by what?
- how to testes develop?
- sertoli cells secrete what?
- interstitial (Leydig) cells secrete what?
- SRY gene on Y chromosome
- Wolffian ducts develop into epididymis, vas deferens and seminal vesicle (with testosterone)
- Mullerian ducts degenerate –> induced by AMH
- testes develop then descend into scrotum (with testosterone)
- sertoli cells secrete anti-Mullerian hormone (AMH) + factors needed for differenciation
- Leydig cells: secrete androgens: testosterone and dihydrotestosterone (DHT)
do females have testosterone and dihydrotestosterone (DHT?)
- how to convert testosterone to DHT?
- females have testesterone but no DHT
- using 5a-reductase
describe female embryonic development
- without which gene?
- what ducts develop into what? under what stimulus?
- which ducts degenerate? under what stimulus?
- ________ genitalia takes on female characteristics (without which hormone?)
- without SRY gene! so no AMH
- Mullerian ducts develop into upper portions of vagina, uterus and Fallopian tubes (without SRY and AMH + with female specific genes)
- Wolffian ducts degenerate (without testosterone)
- External genitalia –> without DHT
- function of vas deferens?
- function of testicles?
- function of epididymis
- vas deferens = bring sperm to urethra
- testicles: production of spermatozoid
- epididymis: for maturation of sperm –> lots of prots and enzymes to make sperm ready to fertilize egg
when does the sexual development/differentiation happen in the human embryo?
- 6 weeks: cannot visually identify male vs female
- around10 weeks, some differentiation can be seen
internal organs:
Male vs female:
- gonadal cortex form what?
- gonadal medulla forms what?
- wolffian duct?
- mullerian duct?
MALE:
- gonadal cortex regresses
- gonadal medulla forms a testis
- wolffian duc froms epididymis, vas deferens and seminal vesicle (testosterone present)
- Mullerian duct regresses (AMH present)
FEMALE:
- gonadal cortex forms ovary
- gonadal medulla regresses
- wolffian duct regresses (no testosterone)
- mullerian duct becomes fallopian tube, uterus, cervix and upper 1/2 of vagina (AMH absent)
External organs:
Male vs female:
- genital tubercle forms what
- urethral folds and grooves form what?
- labioscrotal swellings form what?
MALE:
- genital tubercle forms gland penis
- urethral folds and grooves form shaft of penis
- labioscrotal swellings form shaft of penis and scrotum
FEMALE:
- genital tubercle forms clitoris
- urethral folds and grooves form labia minora, opening of vagina and urethra
- labrioscrotal swellings form labia majora
why is scrotum away from body?
to regulat temperature bc sperm cannot handle heat inside body
eggs (other name?) VS sperms:
- small/large cells, motile/non-motile and must be moved/move by themselves?
- do eggs or sperms have a longer lifespan?
EGGS (or ovocytes)
- large
- nonmotile
- must be moved
SPERM:
- small
- motile
- use a flagellum to swim
*sperm have a longer lifespan! –> can survive longer bc of seminal liquid/semen and uterine environment VS egg: if too old, has chromosome issues
- gametogenesis begins in _______
- begins with _______ to increase numbers
- ______ results in production of _______ cells –> 3 steps
- is the timing of gametogenesis the same in males and females?
- begins in utrero
- begins with mitosis to increase numbers
- meiosis produces haploid cells:
1. DNA duplication into primary spermatocyte or primary oocyte
2. First meiotic division to produce secondary spermatocyte/oocyte
3. second meiotic division to produce gamete - timing different in males and females! –> males produce sperms all their lives vs females have a fixed number of eggs at birth
MALE GAMETOGENESIS
- at birth, germ cells are _____A______ –> at what stage? (mitosis, meiosis 1 or meiosis 2)
- that stage resumes when? –> resting pool of _____A______ –> production through life?
- germ cells are spermatogonia –> at birth, males have not progressed past mitosis –> spermatogonia are quiescent until puberty
- mitosis resumes at puberty –> resting pool of spermatogonia
- continuous production of sperms from puberty through life
FEMALE GAMETOGENESIS:
1. oogonia complete _____ stage by which month of fetal development?
- resting pool of oogonia?
2. females are born with what?
3. at birth, start which stage (mitosis, meiosis 1 or meiosis 2)? –> arrest until what?
4. primary oocytes mature at what rhythm?
5. what happens if fertilization?
- oogonia complete mitosis stage by 5th month of fetal development
- no resting pool - females are born with all eggs (primordial follicles that contain primary oocytes) (around 5000) that will be produced
- at birth, first steps of meiosis start and arrest until puberty (still primary oocytes at this point) (4n)
- primary oocytes mature once a month at puberty until menopause –> a group of primordial follicles will start developing and maturing –> some will die + 1 will release a secondary oocyte/egg (2n) + first polar body (2n) (excess of DNA leaving)
- if fertilization, meiosis 2 happens –> secondary oocyte divides into a mature gamete (n) + second polar body (n) (only released after fertilization)
what does it mean if you see a 1st polar body? vs 2nd polar body?
- 1st polar body: means oocyte was mature
- 2nd polar body: means there’s fertilization
do both sexes produce androgens and estrogens?
ANDROGENS:
- are dominant in male/female/both?
- most __________ comes from where?
- which enzyme converts androgens to estrogens?
ESTROGENS:
- dominant in male/female/both?
- what organ produce estrogens (2), progestins (1) and androgens?
*adrenal gland secrete small amounts of what?
- yes!
ANDROGENS - dominant in males
- most testosterone comes from testes/testicles
- aromatase converts androgens to estrogens –> important for follicular growth
ESTROGENS - dominant in females
- ovary produces estrogens (estradiol and estrone), progestins (progesterone/pregnancy hormone) and androgens
*adrenal gland secrete small smounts of sex steroids
in a follicle, which 2 types of cells control secretion of estradiol?
granular cells (Several layers on membrane of follicle) + theca cells (outside of membrane ish)
- which hormone (A) from ________ controls secretion of the 2 anterior/superior? pituitary hormones?
- what are the 2 hormones? what do they do?
- hormone A regulated by what?
- gonadotropin-releasing hormones (GnRH) from hypothalamus controls secretion of 2 anterior pituitary hormones
- Follicle stimulating hormone (FSH) –> regulates gametogenesis in gonads
- Luteinizing hormone (LH) controls production of sex hormones
- GnRH regulated by several hypothalamic peptides including kisspeptin
what inhibits and what activates FSH secretion?
- Inhibins –> inhibit FSH
- activins stimulate FSH + promote spermatogenesis + oocyte maturation + development of embryonic nervous system
how is GnRH, FSH and LH secreted? at what rhythm ish?
in pulses, pulsatile release
- GnRH pulse generator involved in sexual maturity
are LH and FSH present in both males and females?
if so, what are their functions?
yes
MALE:
- FSH: act on sertoli cells to help grow sperm
- LH: act on interstitial cells to produce testosterone/DHT
what environmental factors influence reproductive system in women? (4)
stress, nutrition, daylight, environmental estrogens
what are the 2 external genitalia for men?
- name the subparts for each
PENIS:
- urethra: where sperm is ejaculated
- erectile tissue (corpus spongiosum, corpora cavernosa) –> can absorb a lot of blood –> erection
- glans
- prepuce/foreskin: cover of gland
SCROTUM:
- testes –> to lower temperature to control hormonal secretion
what is circumsision?
surgical removal of the foreskin to expose the glans
what is cryptorchidism?
failure of both testes to descend
- testes develop inside body cavity –> descend to exit and form scrotum
- ie: if hernia, can have cryptorchidism
what are the 3 male accessory glands?
- goal of these glands?
- prostate glands
- seminal vesicles
- Bulbourethral (Cowper’s) glands
GOAL = produce semen containing sperm –> liquid contains fructose (give E), citric acid (to maintain viscosity), vit C, carnitine (help produce E)
testes produce ___A__ and ___B____
- ___A___ produced by _________ where?
- which type of cells produce which type of _____B______
- which cells support ___A____ production? through what? (2)
- produce sperm (A) and hormones (B)
- sperm produced by spermatogonia in seminiferous tubules
- Interstitial cells of Leydig produce testosterone
- Seroli cells support sperm production –> Blood-testes barrier + androgen-binding protein (ABP)
sperm are produced where? how do they reach urethra?
produced in seminiferous tubules –> which leave testicles –> join epidydimis (where the sperms mature/grow a flagella) –> then vas deferens to get to urethra
- how do spermatids undergo transformation into sperm?
- spermagogenesis requires (2)
- through formation os acrosome needed for fertilization! acrosome contains lots of proteins/molecules needed for fertilization
- requires gonadotropins and testosterone
male accessory glands contribute secretions to ___A____
- what is ___A____?
- ___% volume of ___A___ is fluid
- composition of ___A___ (8)
- semen!
- semen = mixture of accessory gland secretions and mature sperm
- 99% volume of semen is fluid
COMPOSITION: - sperm
- mucus
- water
- buffers (neutralizes acidic env. of vagina)
- nutrients (fructose, citric acid, vit C, carnitine)
- enzymes (clot semen in vagina, then liquify clot)
- zinc (association with fertility)
- prostaglandin (to induce uterine contractions to bring sperm into fallopian tubes)
what is vasectomy?
cut the vas deferens to block sperm from leaving epididymis and reaching urethra
difference between primary and secondary sex characteristics?
- what influences primary vs secondary?
PRIMARY:
- internal organs and external genitalia that distinguish males from females
- influenced by testosterone
SECONDARY:
- other traits that distinguish males from females
- ie: body shape, beard and body hair, muscular dev., lowering of voice, libido
- DHT!
what are the external genitalia (3) and internal organs (3) of females? + extra
EXTERNAL GENITALIA:
- vulva/pudendum (exterior of vagina) –> labia majora and labia minora
- clitoris
- urethra lies btw clitoris and vaginal opening
INTERNAL ORGANS:
- vagina (where sperm is deposited) –> hymen
- cervix (region btw end of vagina and beginning uterus
- uterus: myometrium (contract for labor) + endometrium (where placenta will form OR what is discarded during menstruation)
EXTRA:
- 2 fallopian tubes (oviduc) that lead to ovaries –> fertilization takes place in fallopian tubes
- fimbriae: catch egg during ovulation at the end of oviduct
what could cause fertility issue?
MALE:
- not enough sperm count
- sperm morphology problem
- sperm lost motility
…
FEMALE:
- no ovary function –> follicles don’T grow
- fimbriae don’t catch egg
…
what is the endometrium?
glandular epithelium whose structure varies with phases of menstrual cycle
- very irrigated
- secretes a lot of things at the beginning of embryo growth –> after, nutrients come from placenta
cycle of the follicles until end (9)
primordial follicle (with primary oocyte) –> primary follicle –> secondary follicle –> early tertiary follicle –> dominant follicle –> ruptured follicle –> release of egg –> corpus luteum (yellow body) –> regressing corpus luteum/corpus albicans (white body)
which part of ovary contains follicles vs blood vessels vs nerves?
- cortex contains follicles
- medulla contains blood vessels and nerves
- also outer connective tissue and inner connective tissue (stroma)
describe primordial –> primary –> secondary –> tertiary follicles
PRIMORDIAL:
- primary oocyte surrounded by granulosa cell (granulosa cells will become cumulu cells)
- if unselected for maturation, will undergo atresia (when follicles fail to develop)
PRIMARY:
- primary oocyte grows
- granulosa cells divide and produce hormones (estradiol)
SECONDARY:
- follicles grow larger (multiplying granulosa cells)
- theca cells begin to form
- some follicles fail and become atretic
TERTIARY:
- formation of a large fluid filled cavity (antrum) –> indicative of health of follicles
- follicle that remains from pool becomes the dominant follicle –> release egg/ovulation
which 2 cells are necessary to form estrogen?
- granulosa cells and theca cells!
- each form 1/2 of estrogen
it is only follicle that grows during follicular development or egg also grows?
- what also multiplies?
- both grow! the primordial follicle is smaller than the egg in the dominant follicle!
- granulosa cells increase layers as follicle grows
what are the different stages in the ovarian/follicle cycle vs the uterine/endometrium cycle?
OVARIAN:
1. follicular phase (menses + proliferative phase of uterine cycle)
2. ovulation (btw follicular and luteal phase)
3. luteal phase with corpus luteum (same as luteal phase)
UTERINE:
1. menses
2. proliferative phase
3. secretory phase
what happens during the early follicular phase (4) vs mid-to-late follicular phase? (3)
- hormone secretion, endometrium, follicles…
EARLY FOLLICULAR PHASE:
- beginning of growth of primordial follicles is independent of hormones
- + FSH induces growth of tertiary follicles
- granulosa cells and theca cells produce steroid hormones (estrogen)
- AMH = no development of other follicles in this cycle
- endometrium proliferates bc of estrogen
MID-TO-LATE FOLLICULAR PHASE:
- high estrogen becomes positive feedback for FSH = increase FSH
- LH surge
- uterus prepares for implantation, endometrium thickens
what happens during ovulation (3)?
OVULATION:
- peak of LH = ovulation –> follicle ruptures, releasing mature oocyte
- ovulation = lots of broken blood vessels = inflammatory reaction attracts leukocytes that secrete prostaglandins
- mature follicles secrete matrix metalloproteinases (MMP) –> makes the tissue change from granula cells to yellow body (?)
what happens during early to mid-luteal phase (4), late luteal phase and menstruation? (3)
- cells becomes what cells? Secrerion of what? Endometrium. Cervix?
EARLY to MID-LUTEAL PHASE:
- granulosa and theca cells differentiate into luteal cells
- luteal cells secrete inhibitin + mostly progesterons (negative feedback on hypothalamus)
- endometrium prepares for implantation –> deposits lipids + glycogen increases in endometrial cells –> provide nutrients for embryo while placenta develops
- cervical mucus thickens
LATE LUTEAL PHASE + MENSTRUATION:
- no pregnancy –> corpus luteum degenerates into corpus albicans
- progesterone and estrogen levels drop –> leads to increase in FSH and LH secretion
- endometrium sloughs off = menstruation
which hormones influence female secondary sex characteristics? (2)
- estrogens control breast development and fat distribution
- androgens control pubic and axillary hair growth and libido
what is the main hormone that blocks maturation of follicles and ovulation?
progesterone! in both humans and cows
what biomarker is a good indicator of menstrual cycle?
basal body temperature! will increase during secretory phase of uterine cycle, and decreases as menses start
describe changes in FSH, LH, estrogen, inhibin and progesterone throughout menstrual cycle?
FOLLICULAR PHASE
- FSH pretty constant, decreases a bit before ovulation + small peak at ovulation
- estrogen slowly increases during phase as follicle grows (follicle produces estrogen). As estrogen peaks, it causes LH to peak
- LH is low, until high [estroge] causes LH peak
- inhibin has a little peak at ovulation
- progesterone starts increasing a bit at ovulation
LUTEAL PHASE:
- progesterone blocks FSH and LH secretion so FSH and LH are low
- progesterone increases (produced by corpus luteum) and starts decreasing as corpus luteum becomes corpus albicans
- inhibin has a peak at similar ish time as progesterone peak + little estrogen peak
Hormonal control:
1. Early to mid-follicular phase:
- low/high levels of estrogen exert positive/negative feedback to (3)
- estrogen has positive feedback on what?
- AMH prevents what?
2. late follicular phase and ovulation
- high estrogen output has positive feedback on what?
- at some point, what causes inhibin to be secreted? –> consequence?
- what (2) cause LH surge?
3. early to mid-luteal phase
- increase in which 3 hormone causes negative feedback on (2) –> consequence?
4. late luteal phase:
- what dies? consequence?
- low levels of estrogen have negative feedback on GnRH, FSH and LH
- estrogen has positive feedback on estrogen secretion by follicle (as it grow)
- AMH prevents more follicles from developing - high estrogen output has positive feedback on GnRH to secrete more FSH
- at some point, follicle is so big that inhibin is secreted –> blocks FSH
- rising levels of estrogen and progesterone = LH surge - increase in estrogen, PROGESTERONE and inhibin causes negative feedback on GnRH to block FSH and LH = no follicular growth
- corpus luteum dies = estrogen and progesterone levels fall –> GnRH resumes tonic secretion of FSH and LH which start follicular development for new cycle
- fertilization requires ____A_____
- what is _____ A_____? –> enables what? occurs where?
- requires capacitation!
- capacitation = final maturation step! enables sperm to fertilize an egg + occurs in the female reproductive tract
- where does fertilization occur?
- it must occur within ____ hours of ovulation
- reaction between what 2?
- fusion of sperm and egg triggers ________ reaction –> what is released to prevent polyspermy?
- how is the haploid/diploid cell created?
- in fallopian tubes!
- within 24h of ovulation
- zone pellucida and acrosomal reaction
- triggers cortical reaction –> cortical granules are released to prevent polyspermy
- diploid cell created by nuclear fusion
how does zona pellucida prevents polyspermy? (3)
- zone pellucida has receptors –> when sperm arrives, it binds to a receptor + releases content of acrosome
- contents of acrosome changes stuff in zona pellucida –> which secretes cortical granules
- cortical granules block other sperms from binding to another receptor
- what triggers the cortical reaction?
- does the entire sperm enter the egg cytoplasm?
- does oocyte nucleus complete meiotic division before or after sperm nucleus enters cytoplasm of egg?
- fusion of sperm and egg plasma membranes
- no! only nucleus of sperm enters! + acrosome is released to prevent polyspermy
- after sperm enters!
at which day is there:
- fertilization
- cell division takes place
- blastocyst reaches uterus
- blastocyst implants
*when is it called a blastocyst?
- ovulation
Day 1: fertilization
Day 2-4: cell division takes place
Day 4-5: blastocyst reaches uterus
Day 5-9: blastocyst implants
- blastocyst = beginning of differentiation in cells!
- developing embryo forms a ______ ______ when it reaches the uterus
- what consists of the extraembryonic membranes? (4) forms what ish?
- forms a hollow blastocyst
1. chorion forms the placenta
2. amnio secretes amniotic fluid
3. allantois forms umbilical cord
4. yolk sac degenerates early - forms placenta ish
*chorionic villi of placenta surrounded by maternal blood, nutrients, gases and wastes
placenta secretes which 4 hormones during pregnancy? + explain
- Human chorionic gonadotropin (hCG)
- maintenance of corpus luteum
- what is tested during pregnancy tests! –> detected up to 48h after implantation - human chorionic somatomammotropin (hCS):
- also called human placental lactogen (hPL)
- necessary for breast development and milk production (lactation)
- affects maternal metabolism - estrogen:
- helps develop milk-secreting ducts in breasts
- lower levels than progesterone - progesterone:
- maintains endotrium
- placenta takes over progesterone production –> corpus luteum degenerates
