S5 getting pregant Flashcards
how is semen derived
seminal plasma from accessory glands of the male reproductive tracts
seminal vesicles - 60%. Alkaline fluid that neutralizes acid. Contains fructose (ATP production), prostaglandins (increase female smooth muscle contraction), clotting factors
Prostate - 25% milky acidic fluid. Contains proteolytic enzymes (break down clotting factors), citric acid (ATP production for sperm)
Bulbourethral glands : 5 %. Alkaline mucus, (lubricates tip of penis)
what are the normal values of semen analysis ?
volume of ejaculate - 2-6ml
viscosity - liquifaction in 1 hr
pH - 7-8
count - >_ 20 million/ml
describe the human sexual response
excitement phase - psychogenic or somatogenic stimuli
plateau phase - stimulus maitained
orgasm phase - if stimulus reaches the threshold, orgasm occurs
resolution phase - return to haemodynamic norm followed by refractory period
what are the requirements of a erection
sinusoidal relaxation
arterial dilation
venous compression - from increased blood flow to the corpus carvenosa, causing sinusoid spaces to expand and push up against the tunica albuginea
parasympathetic innervation. pelvic nerve and pelvic plexus
describe the physiological processes involved in erection of the penis
activation of parasympathetic NS and inhibition sympathetic arterial vasoconstrictor nerves
ACh acts on M3 receptors raising Ca 2+, this activates eNOS, more NO produced so vasodilation of arterioles in corpus carvenosa — > increased penile blood flow
testes begin to elevate
what is erectile dysfunction
psychological (descending inhibition of spinal reflexes)
tears in fibrous tissue of corpus carvenosa
vascular damage (arterial and venous)
drugs
what is the mechanism for viagra ?
inhibits cGMP breakdown in the corpus carvenosa, increasing NO so increasing vasodilation, allowing increased penile blood flow to cause erection
describe the physiological processs involved in emission
movement of semen into prostatic urethra. Sympathetic NS causes smooth muscle contractions and contraction of IUS and EUS ( prevention of retrogade ejaculation)
describe the mechanism of ejaculation
expulsion of semen. Glands,ducts, bladder internal sphincter and IUS contract, EUS relaxes. Internal urethra fills and stimulates the pudendal nerve causing contraction of penile urethra, causing semen expulsion
erection : symp inhibited (reduction of tone at arterioles ) , parasymp active
ejection : symp active
what changes occur in the female tract during the menstrual cycle
in early cycle, lots of oestrogen present so mucus is thin and stretchy (spinnbarkeit mucus) so can facilitate the entry of the male gamete into the female tract
after ovulation oestrogen and progesterone are present, so mucus is thick and sticky so limits access of sperm or bacteria into the female tract
sperm deposits onto the cervix where the semen undergoes coagulation. Site of fertilisation is in the ampulla
what is the fern test ?
detection of a fern pattern in cervical mucus when it has been dried on a glass
presence of what substance confirms pregnancy ?
HCG presence confirms pregnancy. Speculum placed in the vagina to view cervix
describe how sperm is transported through the cervix and uterus
days 14-28 of menstrual cycle is the uterine secretory phase, a hospitable environment for fertilisation and implantation. Oxytocin stimulates uterine contraction following sperm deposition in the vagina
what is capacitation ?
sperm glycoprotein coat is removed to allow binding to the zona pellucida of the oocyte, acrosomal enzymes are exposed so can initiate acrosome reaction, tail movement changes from beat to whip like action. This allows sperm to penetrate the corona radiata of follicular cells and the ZP
describe the acrosome reaction
sperm contacting the corona radiata push through granulosa cells, sperm surface receptors bind to ZP3 proteins of the zona pellucida triggering the acrosome reaction
acrosomal enzymes digest the path through ZP, one sperm penetrates and fuses with the plasma membrane of the oocyte, sperm moves into the cytoplasm –> zygote. Polyspermy is blocked: cortical reaction
what is the fertile window ?
spermatozoa survive 48-72 hr in female tract. Oocytes 6-24 hr (max)
fertile period : sperm deposition up to 3 days prior to ovulation or day of ovulation
describe how fertilisation occurs
one sperm penetrates leading to fusion of plasma membrane
cortical reaction block polyspermy : in oocyte , waves of Ca2+ spikes convert the oocyte membrane so no further sperm can fuse, preventing fertilisation of more sperm
cortical reaction also causes resumption of meiosis 2
oocyte completes meiosis II
pronuclei of male and female move together and form a diploid zygote
mitotic spindle forms leading to cleavage
what happens after fertilisation
each cell at this stage of development is totipotent i.e has capacity to become any cell type
morula : 16 cell stage, 3-4 days following fertilisation, embryo moves into uterus
blastocyst stage : 5 days post fertilisation, morula develops the fluid - filled blastoceole , loss of totipotency, embryoblast/inner cell mass —> embryo, trophoblast/outer cell mass –> placenta (produces HCG)
hatching : digestion of ZP by enzymes from trophoblast, blastocyst hatches from ZP, can now interact with uterine surface to implant
implantation : outer cell mass (trophoblast) interacts with endometrium, which controls the degree of invasion. Progesterone primes the endometrium, the conceptus is nourished in uterine fluid, trophoblast adheres to endometrium
what is contraception
any method to prevent pregnancy
- blocking transport of sperm to avoid fertilisation of oocyte
- disrupting the HPG axis to interfere with ovulation
- inhibiting implantation of the conceptus into the endometrium
what are examples of natural contraception
fertility awareness - indicators like cervical secretions , basal body temperature (prog from CL increases temp), length of cycle
lactational amenorrhoea - breastfeeding suppresses GnRH release so delays ovulation up to 6M after birth
what are the advantages or disadvantages of natural contraception
adv - no hormones , no contraindications
dis adv - not as effective, unreliable, No STI protection
what are examples of barrier contraception
male/female condom
female diaphragm
what is the mechanism, adv and dis adv of condoms
physical barrier prevents sperm entry into cervix
protects against STIs
male latex sensitivity
what is the mechanism, adv and dis adv of female diaphragm
used with spermicide making an additional chemical barrier
insert any time before intercourse
spermicide can cause a local reaction
