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