7. Conception & Contraception Flashcards
How many sperm are produced per ml
How many sperm are contained per ejaculate
What proportions are normal / have abnormal morphology
How long post-ejaculation does the ejaculate liquefy
20-200 million
> 40 million
60% swimming forward vigorously
What does the secretions from seminal fluid contain & what are their functions
Alkaline fluid:
neutralises acid in male urethra & female reproductive tract
Fructose:
Energy for sperm
Prostaglandins
Clotting factors (Fibrinogen): Holds sperm in place after ejaculation, before liquefaction
What do the secretions from the prostate gland contain & what are their functions
Milky, slightly acidic fluid
Proteolytic enzymes:
Break down clotting factors, re-liquefying sperm in 10-20mins
Citric acid
Phosphatase
What does the secretions from the bulbourethral (cowper’s) glands contain & what is their function
Alkaline fluid
Mucous:
Lubrication @ end of penis & urethral lining
Where are sperms moved to just prior to ejaculation
How does this occur
Into prostatic urethra
Due to peristalsis of vas deferens& secretions of seminal vesicles
Describe the mechanism of ejaculation:
How is it controlled
What occurs as a consequence
A spinal reflex
Sympathetic nervous system control (L1, L2):
Contraction of glands & ducts (smooth muscle)
Bladder & internal sphincter contracts (prevents entry of semen into bladder)
Rhythmical striatal muscle contractions (pelvic floor, Ischiocavernosus, bulbospongisus, hip & a all muscles)
Describe the harmodynamic changes in erection
Inhibition of sympathetic arterial vasoconstrictor nerves
Activation of parasympathetic nervous system
(Pelvic nerve, her parasymp=vasodilation, release Ach @ M3 receptors, rise in Ca2+ = activation of NOS to form NO)
Activation of non-adrenergic, non-cholinergic nerves to arteries also releases NO
Central helical arteries in corpora cavernosa straighten, enlarging lumen
Bulbospongiosus & ischiocavernosus muscles compress veins egressing from corpora cavernosa
Impeding return of venous blood
Dilation of arteries & compression of veins = corpora cavernosa engorged with blood near arterial pressure
Erectile bodies turgid
Describe how the release of nitrous oxide causes vasodilation
NO diffuses into & causes relaxation smooth mucs: Increased NO = Formation cGMP = less Ca2+ taken up into stores = less actin/myosin cross bridges = smooth musc relaxed Vasodilation
Erectile dysfunction:
What is the epidemiology
What are the possible causes
What is the the possible treatment & how does it work
40% 40 year olds, 70% 70 year olds
Psychological
Tears in fibrous tissue of corpora cavernosa
Vascular (most common)
Blocking NO: alcohol, anti hypertensives, diabetes
Viagra: inhibits breakdown of cGMP, maintaining erection
(Less Ca intracellularly = less actin/myosin bridges = vasodilation)
What physiological changes occur in the female to facilitate coitus
Vaginal lumbrication
Swelling & engorgement of external genitalia
Internal enlargement of vagina
Cervical mucus:
Oestrogen = abundant, clear, non-viscous
Progesterone + oestrogen = thick, sticky mucus plug
Describe the process involved in sperm transport through the cervix & uterus
Immediately after ejaculation, semen coagulates
(clotting factors:fibrinogen)
10-20mins later, semen re-liquefies
(by enzymes on prostatic secretions)
Majority of sperm don’t enter cervix; lost be leakage
Those that do enter uterus travel 15-20cm to reach uterine tube within a few hours
How is sperm transported
Own propulsive capacity
Fluid currents caused by action of ciliates cells in uterine tract
Describe the process of capacitation
Further maturation of sperm in female reproductive tract (6-8hrs)
Sperm cell membrane changes to allow fusion with oocyte cell surface (removal of glycoprotein coat)
Tail movement changes from beating to whip like action
Sperm become responsive to signals from oocyte
Describe the acrosomal reaction
(Acrosome = sperm outer shell)
Capacitated sperm comes into contact with oocyte zona pellucida
Membrane fuse = start of reaction
Acrosome swells & lubricates contents by exocytosis
Proteolytic enzymes & further binding facilitate penetration of zona pellucida by sperm (approx 15 mins)
What are capacitation & acrosomal reaction both induced by
Influx of calcium
Rise in cAMP in spermatozoa
What is:
Primary oocyte
First polar body
Secondary oocyte
Ovum = primary oocyte
completion of 1st meiotic division produces:
Secondary oocyte (haploid no of chromosomes & bulk of cytoplasm)
First polar body (remaining haploid no of chromosomes)
Describe the structure of the secondary oocyte
Surrounded by follicular cells (cumulus) embedded in gelatinous matrix
Describe the process of fertilisation of the ovum
Secondary oocyte arrives at ampulla; main site of fertilisation
Only 1 sperm penetrates cytoplasm of ovum
Egg completes meiosis II (pro nuclei: 2 sets chromosomes)
Nucleus fuses with nucleus of ovum = zygote (pronuclei fusion)
Within few hrs, zygote begins to divided mitotically: clevage (totipotency)
Forms ball of cells: morula, then hollow structure: blastocyst (loss totipotency)
Blastocyst moving down uterine tubes & after a day or so in unsterile cavity, attached to uterine endometrium: implantation (6 days after ovulation)
Describe the structure of the blastocyst
Outer layer: trophoblast
Surrounds embryo
Sticky trophoblasts over inner cell mass adhere to endometrium & release hCG (can detect clinically)
Inner cell mass: becomes embryo
Describe the main methods of contraception
Natural: abstinence, coitus interruptus, rhythm method
Vasectomy: divide vas deferens & prevent sperm entering ejaculate
Barrier methods: condoms, diaphragm, cap
Hormonal contraception (tablets, progesterone depot/implant) progesterone (thick mucus plug & -ve feedback to hypothalamus/pituitary) Oestrogen (-vely feeds back on anterior pituitary)
Sterilisation: occlude Fallopian tubes
Intrauterine contraceptive device:
inert copper (interferes with endometrial enzymes, implantation, sperm transport into Fallopian tube)
Progesterone impregnated
Post-coital contraception: combined or progesterone only
Define:
Infertility
Primary infertility
Secondary infertility
What proportion of couples does it affect
Failure to conceive within 1 year
Primary: no previous pregnancy
Secondary: previous pregnancy (successful or not)
Affects 15% of couples
Describe the male causes of infertility
Abnormal sperm production
Obstruction of ducts
Hypothalamic/pituitary dysfunction
What is a normal semen analysis
Volume >2ml
Sperm count > 20 million per ml
Motility >50%
Morphology > 50%
What are the female causes of infertility
Anovulation:
Hypothalamic (e.g. Weight loss, exercise, stress)
Pituitary (e.g. Tumours, necrosis)
Ovarian (e.g. Ovarian failure, menopause, radio/chemotherapy)
Induction of ovulation:
Anti-oestrogen (reduce -ve feedback to hypothalamus/pituitary)
Gonadotrophins
GnRH agonists
Tubal occlusion:
E.g. Sterilisation, PID
PCOS:
Increased androgens, LH/FSH ratio, insulin resistance
How might you differentiate between possible causes of female infertility
Hormonal levels:
LH
FSH
oestrogen
Describe the management of infertility
Regular unprotected intercourse
Ovulating? Induce ovulation
Patent tubes?
Adequate sperm count?
What is the normal volume of ejaculate fluid
2-4ml
