Repro Session 7 Flashcards
what happens to semen immediately after ejaculation?
coagulates due to action of clotting factors- fibrinogen and vesiculae
function of coagulating sperm immediately after ejaculation?
to prevent their physical loss from the vagina
what happens after coagulation of semen?
it then liquefies by action of enzymes derived from prostatic secretions- fibrinolysis
what maturational changes do sperm undergo on their passage through the uterus to the uterine tube?
capacitation and acrosomal reaction, which results in them acquiring a full capacity to fertilise ovum
changes first began during their transport from testis to epididymis, and continuing during their storage there until ejaculation
how are capacitation and acrosomal reaction induced in spermatozoa?
by an influx of calcium and rise in cAMP
describe the process of capacitation of sperm
removal of glycoprotein coat promotes changes in sperm cell membrane. Tail movements change from waves to whip-like thrashing movement, propelling sperm along, and they become responsive to signals from oocyte.
what marks the start of the acrosomal reaction?
the membrane fusion when a capacitated sperm come s in contact with the occyte zona pellucida
how is sperm helped to be moved along seminiferous tubules?
by fluid secreted from Sertoli cells
phases of coitus?
excitement- vasodilation
plateau
orgasmic- further stimulo
resolution (+/- refractory period)- vasoconstriction, no physiological refractory period in females where sex arousal can not occur for mins-hrs, latency
what haemodynamic changes causing erection occur?
Must be vasodilation via:
inhibition of S.arterial vasoconstrictor nerves
PNS activation- unique as PNS doens’t normally act directly on blood vessels
activation of non-adrenergic, non-cholinergic AN nerves to arteries, releasing NO
importance of NO for erection?
ACh released from post-ganglionic PNS neurones onto endothelial cell and binds to M3 receptor- Gq- PLC activation, with IP3 release, acts on IP3 receptors to cause increase in IC Ca2+, which activates NOS and so forms NO, which then diffuses into vascular smooth muscle cell and causes relaxation through gunalyl cyclase stimulation, increase cGMP, PKG activation, decrease Ca2+.
NO also released directly from non-adrenergic, non-cholinergic neurones
mechanism of action of viagra?
inhibits cGMP bdown, so more around to activate PKG, and reduce IC Ca2+ conc within vascular smooth muscle cell, inducing relaxation, hence vasodilation
what is the female sexual response?
blood engorgement and erection: clitoris, vaginal mucosa, breast and nipples
glandular activity- vaginal vestibule
sex excitement as in male
with or without orgasm as not essential for fertilisation- only occurs with ejaculation in male- need orgasm
no physiological refractory period
efferents of penile erection?
pelvic nerve- PNS
pudendal nerve-somatic
causes of erectile dysfunction?
psychological- descending inhibition of spinal reflexes
tears in fibrous tissue of corpora cavernosa as unable to stop venous drainage necessary to maintain erection
vascular- arterial and venous e.g. diabetes
drugs e.g. anti-hypertensives, alcohol
factors which block NO?
diabetes, alcohol, anti-hypertensives
how does fibrous tissue of corpora cevernosa help maintain erection?
very tight to prevent venous drainage
why is withdrawl a poor method of contraception?
live sperm are present during emission as spermatozoa move from vas deferens into prostatic urethra, despite ejaculation having not yet took place, so some leakage of live sperm into female before ejaculation
describe processes involved in emission and its control
sperm from epididymis moves through vas deferens to prostatic urethra, via vas deferens peristalsis under SNS control
mainly SNS control, but PNS control of glandular secretions
accessory gland secretions e.g. bulbourethral- pre-ejaculate- alkaline, lubricates urethra and neutralises any acid, control via PNS
describe mechanism of ejaculation
spinal and cerebral reflex
SNS control- L1 and L2
contraction of smooth muscle of glands and ducts, bladder internal sphincter contracts- involuntary control- hypogastric nerve T10-L2 to prevent backflow of semen into bladder that could cause dry orgasm,
rhythmic striated muscle contractions- pelvic floor, ischiocavernosus, bulbospongiosus, hip and anal muscles
PNS may be involved
normal ejaculate volume?
2-4ml
normal sperm concentration of ejaculate?
20-200 million sperm per ml
within how long does liquefaction of sperm occur after ejaculation
1 hour
important clotting factor produced in seminal vesicle secretion?
semenogelin
importance of seminal vesicle secretion being alkaline?
neutralise acid in male urethra from urine, and female vagina, alkalinity better for sperm survival
typically, over which days of uterine cycle does uterine proliferation take place and why?
days 7-14
oestrogen increasing due to production from ovaries: FSH stimulates granulosa cells to produce aromatase which can convert androgens produced by theca interna under LH influence to oestrogens- oestradiol namely
how might oxytocin help sperm transport?
role in rhythmic uterine movements
why do numerous sperm need to reach fertilisation site?
in order to disperse zona pellucida
viable period for oocytes?
6-24hr
when is the fertile period and why?
up to 3 days before ovulation or day of ovulation= 14 days before menstruation occurs, as sperm viable for 48-72hrs and must allow time to travel to ampulla of fallopian tube for fertilisation
outer part of ovum that sperm must push through for fertilisation?
granulosa cells
which cells release hCG from conceptus?
syncytiotrophoblast
what do proteins on sperm head bind to on ovum?
ZP3 proteins of zona pellucida, receptor= species specific
what does binding of proteins of sperm cell to ZP3 receptors trigger?
acrosomal reaction
why is polyspermy blocked after fertilisation?
cortical granules in oocyte cytoplasm, in cortical reaction, release chemicals which stop any further sperm as cause hardening of ZP
importance of cleavage not increasing size of cells from mitosis?
morula would be unable to get into the uterus as still passing along uterine tube
what may happen if blastocytst implantation is close to cervix?
early miscarriage
common implantation site of blastocyst?
2/3 of the way up the posterior uterine wall
how long does conceptus spend in uterine tube before implantation and why?
3 days
awaiting rise in progesterone that results in smooth muscle relaxation in fallopian tube, espec intramural segment, to allow movement into uterus
in an ectopic pregnancy, why does the embryo die?
insufficient blood and nutrient supply to embryo.
egg has failed to be transported
why can severe maternal bleeding occur with ectopic pregnancy?
conceptus invasion into local blood supply- ovarian and uterine arteries, ovarian- from abdominal aorta, uterine- from anterior division of internal iliac, so blood vessel rupture
during which days of uterine cycle is zygote to blastocyst stage?
14-21
how many days after ovulation does implantation commence?
6 days
what does conceptus have to wait for before implanting when floating in intrauterine fluid?
trophoblast to become sticky over inner cell mass by developing receptors.
stimulants of penile erection?
psychogenic
tactile- sensory afferents of penis and perineum
changes in female which facilitate coitus?
Vaginal lubrication- vaginal vestibule glandular activity
Swelling and engorgement of the external genitalia- blood- vasodilation
Internal enlargement of the vagina
Cervical Mucus
Oestrogen – Abundant, clear, non-viscous mucous, aids sperm transport
Progesterone + Oestrogen – Thick, sticky mucous plug
ischiocavernosus and bulbospongiosus innervation
Pudendal (S2-S4)
how many sperm penetrate ovum cytoplasm?
Only one sperm, and its nucleus fuses with the nucleus of the ovum. This forms the zygote.
main action of progesterone when used as a contraceptive?
production of thick, hostile, cervical mucus plug that prevents sperm entry into uterus
examples of natural contraception? what are the disadvantages?
abstinence coitus interruptus (or withdrawal)- may not be effective in preventing pregnancy as sperm present in pre-ejaculate that will enter vagina, also no protection against STIs rhythm method- need regular cycle, would avoid coitus on days 7-16 of uterine cycle=fertile period
what method of contraception prevents sperm entering ejaculate?
vasectomy: vas deferens divided bilaterally, but must ensure ejaculate is free of sperm before relying on it for contraception, so check a few months later.
Sperm phagocytosed by epithelia of vas deferens and epididymis as unable to pass from tail of epididymis to prostatic urethra during peristalsis of vas deferns under SNS stimulation during emission
what are the barrier methods of contraception?
o Condoms- readily available and also protect against STIs
o Diaphragm- Lies diagonally across the cervix, needs correct fitting, does not completely occlude the passage of sperm, holds sperm in the acid environment of vagina and reduces survival time
o Cap- Fits across the cervix- physical barrier
what contraception can be used to prevent sperm passing through cervix?
MUCUS PLUG combined OCP depot progesterone- 3mnthly injectiona progesterone only pill-low-dose progesterone impant
main mode of action for POP and implant
contraception to inhibit ovulation?
hormonal: Comb OCP depot progesterone POP- may inhibit ovulation progesterone implants- may inhibit ovulation
effect of progesterone on GnRH release by hypothalamic neurones?
reduces frequency of GnRH pulses
what contaception can be used to inhibit sperm transport along uterine tube?
sterilisation: clips, rings, ligation
how can implantation be inhibited by contraception?
hormonal- affect receptivity of endometrium
post-coital contraception- combined oestrogen/progesterone high dose, or progesterone only, up to 72 hrs after intercourse, may disrupt ovulation, and may also impair luteal function.
intra-uterine device- copper coil, can be used post-cotal up to 5 days after ovulation
how does an intrauterine contraceptive device work?
inert or copper containing, or progesterone impregnated. Copper interferes with endometrial enzymes, assoc. FB reaction with many inflam. cells, and may also interfere with sperm transport into fallopian tubes, so interferes with implantation.
problems= infection, perforation
define infertility
failure to conceive within 1 yr when not using contraception
what is primary infertility?
infertility with no previous pregnancy
what is secondary infertility?
infertility having had previous pregnancy, whether successful or not
Anovulatory causes of infertility?
Hyperprolactinaemia, weight loss, exercise, stress= hypothalamus
Pituitary tumours- prolactinoma, necrosis- post-partum haemorrhage, insufficent blood to pituitary- sheehan syndrome, may present so many mnths-yrs after birth of child with now inability to conceive, no problems before this birth
Ovarian failure, menopause- premature- <40yrs, radiotherapy and chemotherapy gonadotoxic
PCOS
how do you differentiate causes of anovultation?
look at hormone levels
how can hormone levels distinguish between PCOS and ovarian failure as causes of anovulation?
PCOS: increased LH:FSH, and normal oestrogen
ovarian failure: high LH, high FSH, low oestrogen
when is serum progesterone at its peak?
7 days after ovulation
how could POS be investigated?
ultrasound scan
how is anovulation diagnosed?
serum progesterone level in mid-luteal phase, approx. day 21 (7 days after ovulation)
usually >30, if no ovulation, no CL forms, no rise in progesterone
how can ovulation be induced in patients with anovulation?
anti-oestrogen: clomiphene or tamoxifen, reduce -ve fbk to hypothalamus/pit by preventing oestrogen from binding to receptors to inhibit gonadotropin release, so increase GnRH and FSH
gonadotropins- FSH administration
GnRH agonists- pulsatile to mimic normal secretion
examples of coital problems causing infertility?
vaginismus**
poor erection- may give viagra- inhibit cGMP bdown
causes of tubal occlusion resulting in infertility?
sterilisation- ring, ligation
scarring from infection-salpingitis, PID, endometriosis- endometrial tissue outside uterus-increased PG prod. may promote inflammation ,adhesions and fibrosis
how can tubal occlusion be treated?
tubal surgery- reanastomosis
assisted conception
how is tubal occlusion diagnosed?
laparoscopy and dye insufflation
hysterosalpingogram- dye injected into neck of womb and can look at tubes via X-ray
causes of abnormal sperm production ,resulting in infertility?
testicular disease
duct obstruction- infection, vasectomy
hypothalamic/pit dysfunction
general investigation of infertility?
regualr unprotected intercourse?
ovulating?- regular menstrual cycle, day 21 progesterone?
patent tubes- history of infection/sterilisation?, dye insufflation or hysterosalpingogram
adequate sperm count?->20million per ml, >50% motility, >30% morphology
general tment of infertility?
induce ovulation e.g. anti-oestrogen like clomiphene
overcome tubal occlusion by surgery or IVF
inadequate sperm then artificial insemination by donor? or intracytoplasmic sperm injection
how might fibroids be responsible for infertility?
may distort uterine cavity if SM in location, or physically obstruct fallopian tubes. can be pedunculated
main aim of drugs designed to improve erectile function?
increase penile blood flow
normal range of length of menstrual cycle?
21-35 days
how can the uterine tubes be tested for patency?
hysterosalpinography
how might you establish whether cervical sperm transport is disrupted?
post coital test- collect cervical mucus soon after copulation
