Session 7 Flashcards
Define the term ‘infertility’
Failure to conceive within 1 year
–> investigations
Describe methods of inducing ovulation
Anti oestrogen e.g. clomifine, a selective estrogen receptor modulator to reverse anovulation or oligoovulation
FSH
GnRH agonist
Explain why a couple may have fertility problems
Coital problems
Anovulation - (progesterone day 21) e.g. due to hyperprolactinaemia, pituitary tumours
PCOS - increased androgen, >12 cysts
Tubal occlusion - sterilisation, scarring
Abnormal sperm production - testicular disease, obstruction, HPA dysfunction
Describe the main methods of contraception (and their advantages and disadvantages)
Natural:
Abstinence, coitus interruptus (but sperm in pre-ejaculate), rhythm method (need regular cycle, fertile period day 7-16)
Prevent sperm from entering ejaculate:
Vasectomy (divide vas deferens bilaterally, ensure ejaculate free of sperm, (semi)-permanent)
Inhibit transport along fallopian tube:
Occlude fallopian tube with clips, rings, ligation (beware of ectopic pregnancy)
Inhibit implantation:
Hormonal contraception (OCP, POP, implant, depot), post coital contraception (oestrogen/progesterone high dose), IUD (inert, copper, progesterone, foreign body action, copper toxicity to ova and sperm)
Inhibit sperm passing through cervix:
Combined OCP, depot progesterone, progesterone implant, POP (affects cervical mucus –> thick, hostile)
Prevent sperm from reaching cervix:
Barrier methods (condoms, diaphragm - lies diagonally across cervix, holds sperm in acid environment, cap - fits across cervix, physical barrier), spermicide (most effective when used in conjunction with barrier methods)
Prevent ovulation:
COCP (oestrogen+progesterone - -ve feedback to HPA inhibits follicular development, oestrogen = loss of +ve feedback mid cycle, no LH surge), depot progesterone, POP, progesterone implants (may inhibit ovulation)
List the main constituents of sperm and their origins
Seminal vesicles (60%) - alkaline, clotting factors (semenoglobin), fructose, prostaglandins
Prostate (25%) - milky, slightly acidic, proteolytic enzymes
Bulbourethral glands - alkaline, lubricates
Describe the phases of coitus
Excitement - physical/psychogenic stimuli
Plateau - sustained, continued stimuli
Orgasmic - release of excitation
Resolution (+/- refractory period) - cannot be further stimulated immediately
Describe the physiological processes involved in erection of the penis
Stimulants (psychogenic/tactile) –> efferents (somatic + autonomic), pelvic nerve/pudendal nerve –> haemodynamic changes
Corpus cavernosa vasodilates
Construction of veins maintains erection
Post ganglionic PNS release ACh –> binds to M3 receptor on endothelial cell –> high intracellular Ca2+ –> NOS + NO release
NO direct release from nerves also
NO –> vascular smooth muscle –> relaxation (vasodilation)
Describe the method of action of Viagra
Promotes vasodilation
Prevents breakdown of cGMP
Low Ca2+ pumped back into ER
Maintains vasodilation
List some causes of erectile dysfunction
Psychological - stress, anxiety
Anatomical - tears in fibrous tissue of corpus cavernosa
Vascular - arterial/venous
Drugs - alcohol, anti hypertensives
List the criteria for normal ejaculate
2-4ml 20-200 x10^6 sperm/ml 60% swimming forward vigorously 70% normal morphology Liquefaction within 1hr
Describe the physiological processes involved in and the mechanism of emission
Mainly sympathetic (L1-L2)
Movement of ejaculate into prostatic urethra
Vas deferens peristalsis –> prostatic urethra
Accessory gland secretions from bulbourethral gland
Spinal and cerebral reflex
Contraction of glands and ducts
Bladder internal sphincter contracts (prevents retrograde orgasm)
Rhythmic striatal muscle contractions
Describe the physiological changes in the female which facilitate coitus
Vaginal lubrication
Engorgement of external genitalia, breasts and nipples
Glandular activity
Sexual excitement
Describe the process involved in sperm transport through the cervix and uterus
Cervical mucus (oestrogen) - thin, watery, alkaline Oxytocin - spasmodic contraction of uterus
Describe the mechanisms involved in fertilisation of the ovum
Occurs in ampulla of fallopian tube
Sperm pushes through granulosa
Proteins on sperm head bind to ZP3 proteins of zona pellucida
Binding –> acrosome reaction (acrosomal enzymes exposed to zona pellucida, hydrolyse path)
Polyspermy blocked due to cortical reaction
Egg completes meiosis II –> pro nuclei fusion
Cleavage without growth –> blastocyst
In uterus - implantation occurs 6 days after ovulation
Sticky trophoblast adheres to endometrium
Why does vasodilation occur mainly in the corpus cavernosa
Corpus spongiosum dilating too much would block urethra - sperm would be unable to exit
