Reproductive Physiology Flashcards
where in the testis is sperm produced?
seminiferous tubules
where is testosterone produced in the testis?
Leydig cells
where is sperm stored before ejaculation?
epididymis
what does sperm pass through before it mixes with fluid from the seminal vesicles?
vas deferens (contractile tube)
fluid then leaves duct and into the urethra to mix with prostate secretions
what stimulates testosterone production?
LH (on Leydig Cell)
where is inhibin produced in males?
Sertoli cells
what stimulates inhibin production?
FSH
what production does LH stimulate in males?
testosterone production in Leydig cells
what production does FSH stimulate in males?
inhibin production in Sertoli cells
what will testosterone bind to and what effect will the complex have?
Testosterone binds to androgen binding protein (ABP) which will stimulate:
- spermatogenesis (in the seminiferous tubules)
- sperm maturation (in the epididymis)
by concentrating the testosterone and making it less lipophilic (so it does not leave)
FSH does this too
state the stages of spermatogenesis and what happens in them (product)
- Germ cells
- 44+XY (diploid).
- Mitotic division - Primary spermatocyte
- 44+XY (diploid).
- 1st meiotic division. - Secondary spermatocyte - 22+X, 22+Y (haploid).
- 2nd meiotic division. - Spermatids - 22+X, 22+Y (haploid).
- Spermatozoa - 22+X, 22+Y (haploid).
when is the haploid created in spermatogenesis?
after the first meiotic division
how much sperm is created a day and when does this process begin in a boy?
100-200 million a day
starts at puberty
what does the ovary mainly produce?
gametes (ovum)
steroids (oestrogens and progesterone)
what is the role of the Fallopian tubes (oviducts) ?
sustain oocyte/conceptus
where does the implantation of the conceptus occur?
in the uterus
what are the main steroid producing cells of the ovarian follicle and which steroids are produced by them?
thecal–> androstenedione (oestrodiol precursor)
granulosa–> aromatase enzyme–< uses androstenedione–> oestradiol
produce progesterone in the second half of MC
what cells in the ovarian follicle produce oestrogen precursors? what stimulates this?
Thecal cells
stimulation by LH
what cells in the ovarian follicle eventually produce oestradiol and progesterone?
granulosa cells
stimulation by FSH
what is the role of progestogens?
maintain endometrium
what is the role of oestrogens?
stimulate the proliferation of the endometrium
what are the cycles that make up the menstrual cycle?
endometrial and ovarian cycle
what are the processes that occur in the endometrial cycle?
phases:
- menstruation
- repair and proliferation
- secretory
what are the processes that occur in the ovarian cycle?
- follicular phase
- ovulatory phase
- luteal phase
what stage does FSH and LH stimulate? what is the product of this stage and what will it lead to?
FSH and LH stimulate the follicular phase (growth of ovarian follicle)
this leads to oestradiol production by the aromatase enzymes released by granulosa cells
this will lead to proliferation of the endometrium (increase in thickness, more glands and arteries etc)
what is the effect of producing oestradiol (E2) in the thickening process of endometrium?
E2 production speeds up as follicles grow and will switch to positive feedback from -ve FB
ovulation will occur
what does the corpus luteum produce?
corpus luteam is the “dead body” left behind after the release of the ovum progesterone and E2
(luteal phase)
what is the effect of the E2 produced in the follicular phase?
leads to the repair and proliferative phase where proliferation of the endometrium (increase in thickness, more glands and arteries etc)
what are the effects of the progesterone and E2 produced in the luteal phase by the corpus luteum?
progesterone and E2 will lead to the production of nutrients and other factors
progesterone will also lead to epithelial gland widening, endometrium thickening, increased coiling of spiral arteries
(secretory phase)
overall overlap in endometrial and ovarian cycle
1) menstrual phase: endometrium thin after blood shed
2) follicular phase: FSH and LH lead to growth of ovarian follicle production of E2
3) repair and proliferative phase: endometrial growth
4) luteal phase: after ovum release, progesterone and E2 released by CLut
5) secretory phase: endometrium thickening and maintenance (if fertilisation has occurred)
which hormone stimulates ovarian follicle growth?
FSH
how long does a menstrual cycle on average last?
~28 days (21-35 day range)
can be longer in younger people
can be longer or shorter in older people
how does the HPO axis FB change across the MC?
1) follicular phase: ovary produces E2 which will -ve FB on the pituitary and hypothalamus to decrease LH and FSH
2) mid cycle: ovary produces E2 which will switch to +ve FB on the pituitary and hypothalamus to increase FSH and LH release
3) luteal phase: ovary produced progesterone which will -ve FB on the pituitary and hypothalamus
when does LH release peak?
mid cycle when ovulation is to occur
so does FSH (with a lower peak)
which is the dominant steroid in the follicular/proliferative phase?
oestrogen
which is the dominant steroid in the luteal/secretory phase?
progesterone
how does the thickness vary in the endometrium through the MC?
At its thinnest – 2-4mm.
At its thickest – 7-16mm.
when does basal temperature change during MC?
at time around ovulation
what does the developing follicle release?
Estradiol
what kind of FB is there whilst the follicles grow?
-ve on LH and FSH (follicular phase)
when does FB change to positive?
when the dominant follicle has been selected mid-cycle
the dominant follicle now produces more estradiol so that ovulation can occur
what is the effect of +ve FB in the mid-cycle when the dominant follicle has been selected?
LH surge
ovulation can occur
what does the corpus luteum produce?
produces E2 and progesterone –>-ve feedback on LH and FSH.
what happens when no fertilisation occurs?
E2 and progesterone fall and endometrium enters secretory phase.
overall stages of the menstrual cycle with no fertilisation at the end
- Gradual rise of oestradiol by developing follicle (FSH).
- Follicles grow and –ve feedback on LH and FSH.
- Dominant follicle selected and produces lots of E2 –> –ve feedback switches to +ve feedback –> LH surge.
- Ovulation.
- Corpus luteum produces E2 and progesterone ; switch back to -ve feedback on LH and FSH.
- No fertilisation –> E2 and progesterone fall and endometrium enters secretory phase.
what are the stages of folliculogenesis that occurs the ovum
- Oogonia - 44+XX (diploid).
- Mitotic division. - Primary oocytes - 44+XX (diploid).
- 1st meiotic division. - Secondary oocyte (+polar body)
- 22+X, 22+X (haploid).
- 2nd meiotic division. - Ovum (+ polar body) - 22+X, 22+X (haploid).
which stage of folliculogenesis is associated with the LH surge mid-cycle?
ovulation is associated with the LH surge
- before ovulation the secondary oocyte is stuck inmetaphase 2
- at ovulation, the secondary oocyte has been released
- if fertilisation occurs, 2nd meiosis occurs and the second polar body is released
NB second meiosis only occurs at fertilisation
what are primordial follicles?
follicles produced in the 5 month of the foetal ovary containing the primary oocyte arrested at the first meiotic division
At puberty, they begin to develop further and become primary follicles.
when is the second polar body produced?
the second polar body is generated after the 2nd meiotic division which occurs in the fertilised cell.
when is a haploid produced in oogenesis?
after the first meiotic division
how much time does it take for the arrested primordial follicle to become a secondary oocyte? how does this affect follicle release?
more than a month (3)
The human ovary contains multiple follicles at all stages of development with one dominant (Graafian) follicle at any one time.
The ovaries alternate the release as well (so each one releases one follicle each ~56 days)
how many primordial follicles are there in human ovaries at birth? how many are released in ovulation?
large range from 400,000- 2 million
(~6m primordial follicles at ~20w development then ~1m at delivery of infant)
only 400 released in a life time
when does the 1st meiotic division occur in a girls life?
during embryonic development
but halts at diplotene stage of prophase 1 (primary follicle) which is arrested until puberty
what happens to the follicles at puberty?
the primary oocyte from before birth undergoes 1st meiosis to form secondary oocytes, which then undergo a second arrest until ovulation occurs
what is the system involved in reward and pleasure pathways?
Meso-limbic DA system
which system in involved in the control of movement?
Nigro-striatal tract
which system is involved in regulating fertility and parenting?
Neuro-endocrine pathways
what are the pathways that lead to penile erection?
Increased PNS stimulation to smooth muscles
o Sexy thoughts in brain OR tactile stimulus to penis via brain
– limbic system.
o Spinal cord
– efferent to penis, afferent back.
- via Pudendal nerve.
what are the changes that occur in penile erection?
- (ESEED) increased PNS to SM of pudendal artery.
- Increase activity of NOS and thus NO release.
- NO stimulates cGMP –> vasodilation.
- cGMP inactivated by phosphodiesterase. enzyme - Counteracts SNS-maintained myogenic tone.
- Increases blood flow in corpus cavernosum.
- Compress dorsal vein restricting outflow of blood.
- Urethra not compressed due to corpus spongiosum.
same mechanism in clitorial erection
what type of oocyte is released in ovulation?
2n at meiotic arrest
enters the Fallopian tube and needs to be fertilised in 24 hours before it degenerates
how does the cervical mucous affect fertilisation?
Cervical mucous is hostile to sperm which forms a physical barrier.
Cervical mucous changes at mid-cycle to permit sperm to enter the uterus.
what is the affect of capacitation of the sperm?
matures the spermatozoa
what are the reactions that occur at fertilisation?
1) Acrosome reaction
– penetration of zona pellucida (& Coronal cells).
- Change in Zona Pellucida to stop additional sperm fusing
- Cortical reaction
– hardening of zona pellucida and exclusion of other sperm.
2) Calcium flux.
3) Resumption of meiosis at fertilisation, release of 2nd polar body.
4) Alignment of maternal and paternal chromosomes to generate zygote.
when is meiosis 2 of the egg continued?
after fertilisation (NOTwhen it has been released from the ovary)
what occurs when the maternal pronucleus undergoes meiosis 2?
second polar produced and a maternal pronucleus is formed
paternal pronucleus formed when condensation and expansion of the sperm head occurs
what is the final stage of fertilisation?
mitotic divisons of the DNA occur when they align to the mitotic spindle to produce 2n chromosomes of the embryo
differentiate sexual reproduction, sexual intercourse and biological sex
Sexual reproduction
– produce genetically different offspring.
Sexual intercourse
– required for – sexual reproduction, sexual activity, sexual pleasure, human bonding.
Biological sex
– identifies gender, a result of chromosomes, produces different gametes.
what cells are produced in the primary follicle?
granulosa cells
