Reproduction (SUGER) Flashcards
what does hcg stand for?
human chorionic gonadotrophin
what does hcg do?
stimulates ovarian oestrogen/progesterone prod
what does oestrogen do? (2)
- regulates progesterone levels
- prepares uterus/lactating breasts
what does progesterone do? (2)
- builds up endometrium for support of placenta
- inhibits uterine contraction
what does prolactin do?
increases milk-producing cells
what does oxytocin do? (2)
- caring reproductive behaviour
- causes uterine contractions during labour
what are prostaglandins?
tissue hormones that initiate labour
which hormone stimulates ovarian oestrogen production?
hcg
which hormone stimulates ovarian progesterone production?
hcg
which hormone regulates progesterone levels?
oestrogen
which hormone prepares the uterus and lactating breasts?
oestrogen
which hormone builds up the endometrium?
progesterone
which hormone inhibits uterine contraction?
progesterone
which hormone increases milk-prod cells?
prolactin
which hormone limits uterine activity?
relaxin
which hormone is involved in cervical ripening?
relaxin
which hormone causes contractions during labour and reproductive behaviours?
oxytocin
what is the name for the tissue hormones that initiate labour?
prostaglandins
the plasma concentration of which 2 hormones continuously increase during pregnancy?
oestrogen and progesterone
why does progesterone inhibit uterine contractility during pregnancy?
so that the foetus is not expelled prematurely
for the first 2m of pregnancy: what supplies almost ALL of the oestrogen and progesterone?
corpus luteum
if pregnancy had not occurred, in what time frame would the corpus luteum have been degraded?
2w
which hormone is used as a test for pregnancy
hcg
describe the neg feedback mechanism of hcg
- hcg secreted from developing trophoblasts into maternal blood
- stimulates maternal ovaries to continue to secrete oestrogen and progesterone via neg feedback on maternal gonadotrophin secretion
- this prevents additional menstrual cycles
when does hcg secretion peak
60-80 days after last menstruation
what is prolactin prod by?
pituitary gland
when is relaxin high?
in early pregnancy
drugs used to induce labour may contain what?
oxytocin and prostaglandins
list 4 cardiovascular maternal adaptations
- increased CO
- reduced TPR thus reduced BP
- increased uterine blood flow
- increased plasma/RBC volume
list 2 respiratory maternal adaptations
- increased insp vol
- increased breathing rate
how do veins change during pregnancy?
growing uterus - presses on IVC thus incr lower limb venous pressure - varicose veins
list 3 skin changes during pregnancy
- linea nigra: dark line btwn umbilicus/pubic symphysis
- stretch marks @ site of maximal growth
- increased breast size, areola becomes larger/darkly pigmented, nipples become more erect
define parturition
the birth process; successful transition from intra- to extra-uterine life
what is cervical ripening
- growth/remodelling of cerrvix prior to labour
- involves placental hormones (PGs, relaxin, oxytocin)
summarise labour initiation
- stress –> CRH release –> ACTH release –> cortisol release –> OESTROGEN RELEASE
- oestrogen release –> inhibits uterine progesterone release –> UTERINE CONTRACTIONS
- prostaglandins (PFG2a) and relaxin (from ovaries) relax cervic walls –> DILATION
- baby pushing onto cervix –> oxytocin release –> UTERINE CONTRACTIONS (positive feedback)
what is the main prostaglandin released during labour?
PGF2a
what are the 2 main stages of labour
latent phase (onset - 3cm) active phase (3cm - full/10cm)
when does the placenta begin development
at blastocyst implantation
what are the 3 main placental functions
- metabolism
- transport
- endocrine
what is inside the umbilical cord?
2 umbilical arteries
1 umbilical vein
list the 4 “human chorionic ……” placental hormones
- hc gonadotrophin - LH
- hc somatomammotrophin - mammary development
- hc thyrotropin - thyroxine
- hc corticotrophin - cortisol
list 3 other placental hormones
progesterone, oestrogen, relaxin
at birth, how many primary oocytes are there in primordial follicles?
40k
what happens to oocytes at birth?
arrested in prophase of meiosis 1 until puberty
at puberty, what does the ant pituitary release?
FSH/LH
what is the difference between the follicular and luteal phases of the menstrual cycle?
follicular phase = first 14 days (follicle maturation)
luteal phase = last 14 days (corpus luteus formation)
what are the 6 steps of the follicular phase of the menstrual cycle? (when confident, pick a random number 1-6 and test)
- GnRH released from hypothalamus
- FSH released from ant pituitary (proliferation of granulose follicular cells)
- LH released from ant pituitary (proliferation of granulose cells in follicles)
- Oestrogen released from granulosa cells (stimulates endometrium growth)
- At low levels, oestrogen inhibits release of FSH/LH from ant pituitary
- Inhibin released from granulose cells (inhibits ant pituitary)
what is the order of hormones released during the follicular phase?
GnRH - FSH - LH - Oestrogen
what are the 2 steps of ovulation?
- oestrogen prod reaches threshold - no more neg feedback
2. LH surge causes weakening in follicle wall - mature ovum released
what are the 4 steps of the luteal phase of the menstrual cycle? (when confident pick a number btwn 1-4 n test)
- FSH/LH cause follicle to degrade into corpus luteum
- corpus luteum produces high amounts of progesterone/some oestrogen
- progesterone stimulates endometrium growth - ready for blastocyst
- corpus luteum suppresses FSH/LH prod from ant pit
what happens post luteal phase if implantation occurs?
embryo prod hcg hormone which preserves corpus luteum/endometrium
what happens post luteal phase if there is no more implantation?
low FSH/LH levels causes corpus luteum atrophy which stops progesterone production –> menstruation occurs
what are the 5 steps of fertilisation?
- capacitation - sperm prepares for fertilisation by destabilising membrane
- sperm binds to corona radiata –> reaches zona pellucida
- acrosome bursts –> digests through glycoprotein matrix
- cortical granules release –> hardening of zone pellucida –> no sperm entry
- sperm enters oocyte cytoplasm and fuses with ovum nucleus
what are the 6 steps of implantation?
- syngamy
- cleavage
- compaction
- cavitation and expansion
- hatching
- implantation
what happens during syngamy (and which step/day of implantation is this)?
step 1
day 1
- chromosomes align in prep for mitosis 1
what happens during cleavage (and which step/day of implantation is this)?
step 2
day 2-3
- mitotic division occurs
- totipotent stem cells
what happens during compaction (and which step/day of implantation is this)?
step 3
day 4
- cells flatten
- tight gap junctions between cells
what happens during cavitation and expansion (and which step/day of implantation is this)?
step 4
day 5
- blastocyst formation and increase in size
- zona pellucida thins
what happens during hatching (and which step/day of implantation is this)?
step 5
day 6-8
- blastocyst hatches from zona pellucida
- necessary for implantation
describe primordial follicles
consists of 1 primary oocyte surrounded by a single layer of cells called granulosa cells
what do granulosa cells secrete
- oestrogen
- small amts of progesterone jus before ovulation
- peptide hormone inhibit
what do primordial follicles develop into
primary follicle –> preantral follicle –> early antral follicle –> mature follicle
discuss the selection process of follicles
beginning of menstrual cycle - 10-25 of preantral/early antral follicles begin to develop into larger antral follicles
1 week into the cycle, further selection process - only 1 of larger antral follicles, DOMINANT follicle continues to develop
dominant follicle selected on basis of cond of oocyte/oestrogen prod
non-dominant follicles degenerate
what is a mature follicle aka
graafian follicle
what is the corpus luteum a major source of
progesterone
which cells in the testes have a similarity with granulosa cells
sertoli cells (control microns in which germ cell develops/matures)
what is the epithelia lining the uterus called?
endometrium
what is the myometrium
underlying uterine smooth muscle
what impact does progesterone have on myometrial contractions?
inhibits
progesterone only AFTER ovulation causes the mucus to become thick and sticky… what impact does this have?
forms a plug that prevents bacteria from entering the uterus from the vagina - protects uterus/embryo if fertilisation has occurred
when must sperm be introduced for pregnancy?
5 days before ovulation - 1 day after
how is egg transported?
- at ovulation, the egg is extruded onto the ovary surface
- fimbriae’s smooth muscles cause the fimbriae to pass over the ovary while the cilia beat in waves towards the interior of fallopian tube
- these ciliary motions sweep the egg into the Fallopian tube as it emerges onto the ovarian surface
- once inside the fallopian tube, the eggs moved by the fallopian-tube cilia, the cilia are slow and it takes around 4d for egg to be beaten into the uterus
where does fertilisation occur
ampulla of Fallopian tube
after gamete fusion, in how many hours does egg undergo meiosis 2?
4-7
describe what happens during meiosis 2
- zygote still in fallopian tube
- 2nd polar body degenerates
- 2 sets of 23c (egg + sperm) now known as pronuclei
- pronuclei migrate to cell centre
- DNA replication occurs in prep for 1st mitotic division
- 46 chromosomes organise @ spindle equator
after cleavage, each cell is totipotent; what does this mean
stem cells with capacity to developing into an entire individual (MZ twins occur at some point during cleavage)
how many cells does a blastocyst have
more than 80
what does a blastocyst consist of
outer layer of cells (trophoblast), inner cell mass and central fluid filled cavity
when does implantation occur
day 21 of cycle (embryo reaches uterus day 5/6)
what does the trophoblast diff into
cytotrophoblast
syncitiotrophoblast
what are the 3 phases of embryo implantation
- apposition
- attachment
- invasion
what prevents antigenic rejection of embryo
secretion of interleukin 2
when does the placenta begin to develop
at blastocyst implantation
what does the placenta consist of
a combination of interlocking foetal and maternal tissues
how does the maternal blood enter placental sinuses
via uterine artery
unconjugated bilirubin vs conjugated: which crosses placenta easily
unconjugated
what does SRY stand for
sex determining region on y chromosome
what is MIF (mullein inhibitory factor) released by
Sertoli cells in testes
wat causes MIF to be released
presence of SRY gene
what does DHT (dihydrotestosterone) do?
- development of external male genitalia
- also major role in development of body hair, muscle growth, deep voice etc
which ducts form for females?
mullerian duct (paramesonephric)
which ducts form for males?
wolffian duct (mesonephric)
what is lionisation?
only 1 of a female’s X chromosomes is functional: non-functional X - condenses to form nuclear mass = Barr body
where do m/f gonads derive embryologically from?
urogenital/gonadal ridge
when do the testes begin to develop
week 7
what is testosterone prod by
leydig cells
what impact does testosterone have on wolffian duct
differentiates into epididymis, vas deferent, ejaculatory ducts and seminal vesicles
what does the mullerian duct in females develop into
Fallopian tubes and uterus
do the external genitalia develop from mullerian/wolffian ducts?
no
what are germ cells
cells that develop into sperm/ova
where do germ cells originate from
yolk sac of hind gut
what is the 1st stage in gametogenesis
proliferation of primordial (undifferentiated) germ cells by mitosis
(46c chromosomes replicated, division into 2 daughter cells)
in males, when does mitosis usually occur?
some during foetal life but mostly during puberty (to form primary spermatocytes)
in females, when does mitosis usually occur?
during foetal life (to form primary oocytes)
what is the 2nd stage in gametogenesis
meiosis
results in gametes receiving only 23c from a 46c germ cell
what is crossing over
when 2 non-sister chromatids undergo an exchange of sites of breakage –> results in the recombination of genes on homologous chromosomes
what does the 1st meiotic division result in
males: secondary spermatocytes
females: secondary oocyte (NOTE, the 2nd cell arising from 1st meiotic division = 1st polar body - no function)
what is the timing of the 2nd meiotic division in males/females?
males: continuously after puberty –> spermatids –> mature sperm cells
females: AFTER FERTILISATION of sec oocyte by sperm –> zygote (+ 2nd polar body)
give a brief overview of meiosis 1 and 2
meiosis 1: separates homologous chromosome pairs producing 2 haploid cells (4n - 2n)
- mitosis, but crossing over/independent assortment occurs
meiosis 2: separates duplicated sister chromatids prod 4 haploid cells (2n - n)
- daughter cells divide to form haploid cells
where does meiosis occur in males
seminiferous tubules
where does meiosis occur in females
ovaries
how many ml of fluid is expelled during an orgasm (males) and what does this consist of
2-5ml
- 60% seminal vesicle fluid
- 30% prostatic
- 10% sperm and trace of bulbourethral fluid
what is a normal sperm count
50-120 million/mL
what is semen
fluid and sperm cells
what does sperm serve to do
digest path through cervical mucus
fertilise the egg
how does prostate/seminal vesicle secretion aid sperm
- buffers for sperm protection against vaginal secretions/residual urine in male urethra
- chemicals that increase sperm motility (movement)
- prostaglandins to stimulate female peristaltic contractions
what is the mnemonic for the summary of path of sperm to outside
SREEVE(N)UP
what does SREEVE(N) up stand for
summary of path of sperm to outside
- Seminiferous tubules
- Rete testis
- Efferent ducts
- Epididymis
- Vas Deferens
- Ejaculatory duct
- NOTHING
- Urethra
- Penile Urethra
what does the blood testis barrier ensure
proper cond for germ cell development and differentiation within tubules (Sertoli cells form BTB)
what is another word for undifferentiated germ cells
spermatogonia
where are spermatozoa produced
testis
when spermatogonia divide mitotically @ puberty: they prod 2 types of daughter cells. what are they?
type a & b
what is the difference between type a & type b daughter cells
type a: remain oUTSIDE blood-testis barrier and prod more daughter cells until death
type b: diff into PRIMARY SPERMATOCYTES which move through BTB (which then go onto become secondary spermatocytes –> spermatids –> spermatozoa)
what happens during meiosis 2 in males:
secondary spermatocytes –> 4 spermatids
what happens during spermiogenesis
spermatids diff into spermatazoa by:
- growing tail (flagellum)
- discarding cytoplasm to become lighter
where does spermatogenesis occur
seminiferous tubules bordering Sertoli cells
what happens when sperm formation completes
cytoplasm of Sertoli cells around sperm retracts and sperm released into lumen to be bathed in luminal fluid
what is most of the tail of the sperm made of
flagellum: group of contractile filaments –> whiplike movement capable of propelling sperm at velocity
what is the tip of the nucleus of the sperm covered by
acrosome: protein-filled vesicle containing enzymes to penetrate egg
at birth, how many eggs do the ovaries contain
2-4 million
what is another word for primitive germ cells
oogonia
when do all of the oogonia differentiate into primary oocytes
during foetal life
when does meiosis 1 occur in females
in-utero before week 12
where is meiosis arrested until puberty for females
metaphase 1
in meiosis 1, what happens to 1 of the 2 daughter cells?
secondary oocyte - retains virtually all of cytoplasm (other 1 is 1st polar body, so small and non-functional)
when does meiosis 2 occur in females
when secondary oocyte develops into ovum
when is meiosis 2 arrested until
fertilisation
what is the diff btwn m&f primary oocytes/spermatocytes?
each primary oocyte can only prod 1 ovum
each primary spermatocyte can prod 4 sperms
what is the diff btwn m&f maturation
male: both occurs in testis
females: 1 in ovaries and 1 in Fallopian tube after fertilisation
what does the hypothalamic-pituitary-gonadal axis of males result in:
GnRH in hypothalamus –> FSH/LH release in anterior pituitary
- FSH acts on Sertoli cells –> stimulates initiation of spermatogenesis
- LH acts on Leydig cells –> stimulates testosterone secretion (facilitates spermatogenesis)
how does testosterone inhibit LH secretion (negative feedback mechanism)
- acts on hypothalamus to decrease secretion of GnRH
2. acts directly on ant pit gland to decrease LH response to GnRH
what do Sertoli cells release
protein hormone INHIBIN: acts on ant pit to inhibit release of FSH
what does the hypothalamic-pituitary-gonadal axis of females result in:
GnRH in hypothalamus –> FSH/LH release in anterior pituitary
- FSH/LH –> stimulate oestrogen/progesterone release –> both have pos/neg feedback with hypothalamus/ant pit
after puberty, what happens to GnRH, GHRH (hypothalamus) and FSH, LH, GH (growth hormone)
increase
list some physical changes at puberty for males
9-14 yrs
- testicular enlargement (1st sign)
- facial, pubic, axillary hair growth
- growth spurt
- acne, body odour and mood changes
- spermatogenesis begind
list some physical changes at puberty for females
8-14 yrs
- breast development (1st sign)
- pubic, axillary hair growth
- slight growth spurt
- acne, body odour and mood changes
- menarche (2.5 yrs after start of puberty)
when does pregnancy begin
not at fertilisation but after implantation (1 week after fertilisation)
what are contraceptives
birth control methods that work prior to implantation
define menopause
cessation of menstruation, usually btwn 48-52 yrs when ovaries stop releasing eggs
what are the 8 steps of menopause
- depletion of primordial follicles (approx 40 yrs)
- decrease in follicular oestrogen prod
- gradual increase in FSH/LH (bc of lack of neg feedback from oestrogen)
- inhibit decline (further FSH increase)
- increase in FSH = rapid increase in oestrogen secretion from existing follicles
- shorter menstrual cycles
- as fewer follicles remain, increase in FSH no longer stimulates oestrogen increase (6-12m pre-menopause)
- decreased oestrogen and lack of ova = menopause
what are some signs of menopause (4 typesish)
vasomotor: flushes, sweats, palpitations
psychological: irritability, depression, loss of libido
UG/skin: vaginal/skin dryness, brittle hair/nails
osteoporosis: less bone tissue (reg by oestrogen)
