Repro Session 7 Flashcards
What stimulates formation of the blood-testis barrier?
Testosterone and androgen-binding protein of Sertoli cells
Is LH necessary for spermatogenesis?
No
Which two hormone cans initiate spermatogenesis in the absence of LH?
FSH and testosterone
What is the action of oestrogen secreted by Leydig cells?
Increase sperm viability
Which cells secrete inhibin in the male?
Sertoli
What does a spermatid become after spermiogenesis?
Spermatozoon
What happens in the head of a spermatid during spermiogenesis?
Nuclear condensation
How is the acrosome of a spermatid formed?
Golgi apparatus secrete lysozyme like enzymes into vesicle
What is the function of the acrosome?
Future penetration of an ovum
Where is the acrosome of a spermatid found?
In the head
Describe the mid-piece of a spermatid.
Mitochondria become packed around contractile filaments
How does the tail of a spermatid develop?
Centriole arises and micrtobules grow from it to form axoneme
What is the axoneme?
Shaft of flagellum with 20 micro tubules arranged in 9 doublets and 2 singlets
What happens to excess cytoplasm during spermiogenesis?
Removed with excess organelles by testosterone
What does LH act on to cause testosterone secretion?
Leydig cells
What surface molecules are found on a spermatozoa?
Proteins and carbohydrates
Describe the maturity and motility of spermatozoa.
Mature but lack motility
How are spermatozoa released?
Via spermation from Sertoli cells into lumen of seminiferous tubule
What do Sertoli cells release in addition to spermatozoa?
Testicular fluid
What is the function of testicular fluid?
Carry spermatozoa via peristaltic contractions to the epididymis
What are the surface proteins of spermatozoa covered in when they reach the epididymis?
Seminal plasma proteins
What happens to spermatozoa in the epididymis?
Gain motility, become fertile and be stored
Does storing spermatozoa for several months have an impact in fertility?
No
What happens to spermatozoa that are not released within a few months of arrival at the epipdidymis?
Phagocytosed by epididymal epithelial cells
What are the stages involved in maturation of the oocyte nucleus?
Meiosis I, nuclear membrane disappears, 1st polar body formed, Meiosis II, stop in metaphase II
Where does the 1st polar body formed during oocyte nuclear maturation go?
Perivitelline space
What process are involved in oocyte cytoplasm maturation?
Organelle distribution, protein and lipid synthesis and cytoskeleton dynamics
What happens during organelle redistribution in oocyte cytoplasm maturation?
Mitochondria and ER form granules
What do protein and lipid synthesis during oocyte cytoplasm maturation form?
Cortical granules and lipid drops
What cytoskeleton dynamics take place during oocyte cytoplasm maturation?
Movement of microfilaments to the cortex
How are dizygotic twins formed?
2 eggs are ovulated and fertilised
What happens during the excitement phase of coitus in both the male and female?
Sensory and psychological stimulation activate the limbic system
What is the limbic system?
Instinct and mod part of the brain that initiates sex drive
What are the neural consequences of activation of the limbic system?
Activation of sacral parasympathetic nerves and inhibition of thoracolumbar sympathetic nerves
What are the consequences of activation of the sacral parasympathetic nervous system in the female?
Vasocongestion causing vaginal lubrication, clitoris engorgement, uterine elevation, increased muscle tone, increased HR, increased BP and vaginalis elongation and expansion
How is nitric oxide synthase activated in the male excitement phase of coitus?
ACh acts on M3 receptors of endothelial cells causing an increase in calcium
What is the consequence of NO production from stimulated eNOS in the excitement phase of the male?
Causes arteriolar vasodilation in corpora cavernosa to increase penile bloodflow
What happens in penile filling?
Latency period with increased blood but no erection
What are the end results of the male excitement phase?
Penile tumescence (erection), scrotal skin thickens and tenses, testes elevate and engorge
What is the effect of continued stimulation on muscle tone, HR and BP in the female plateau phase of coitus?
Further increased
What change is visible in the labia minora in the plateau phase?
Deepens in colour
Where is the orgasmic platform found?
Lower 1/3 of vagina
What does the clitoris do during the plateau phase?
Draws under its hood
What is the function of Bartholin mucus secretion in the plateau phase ?
Lubricate vestibule for penis entry
Describe the positions of the uterus and vagina in the plateau phase.
Uterus fully elevated. Inner 2/3 of vagina fully distended
How does activation of the sacrospinous reflex impede venous return in the male plateau phase?
Contracts ischiocavernosus causing compression of the crus penis
What decreases arterial inflow in the male plateau phase?
Intracavernous pressure rising towards systemic circulatory levels
What is the function of stimulation of the Cowper’s and Littre’s glands in the male plateau phase?
Secretions lubricate distal urethra and neutralise urine
What does the thoracolumbar sympathetic reflex cause in the male emission phase?
Contraction of ductus deferens, ampulla, seminal vesicle and prostate
Why do the urethral sphincters contract in the male emission phase?
Prevent retrograde ejaculation
Where does semen pool during the male emission phase?
Urethral bulb
What are the two stages of the male orgasm phase?
Emission and ejaculation/expulsion
What is the neural involvement in the ejactulation phase?
Spinal reflex, cortical control, SNS L1 and 2
What is the action of neural activity in the ejaculation phase?
Contraction of smooth muscles in glands and ducts
What stimulates the pudendal nerve in the ejaculation phase?
Internal urethral filling
What does stimulation of the pudendal nerve cause in the ejaculation phase?
Contractions of genital organs, ischio- and bulbocavernosus
What happens to the orgasmic platform in the female orgasmic phase?
Rhythmically contracts 3-15 times
What does pudendal nerve stimulation in the female orgasm phase cause?
Uterus (fundus to cervix) and anal sphincter contract
What happens to the clitoris in the orgasm phase of coitus?
Remains under hood
Does the inner 2/3 of vagina move during the orgasm phase of coitus?
No, remains motionless
Are multiple orgasms possible?
Yes but only in the female
What are all visible changes in the breast during coitus due to?
Venous engorgement and increased arterial flow
What changes are seen in the breasts during coitus?
Increased breast size, nipples erect, distinct veins, increase in areolar size and sex flush on breasts and upper abdomen
What is the G spot?
Grafenberg spot = area of erotic sensitivity on anterior vaginal wall similar to male prostate tissue
What happens when the G spot is stimulated?
Small amount of fluid released that is enzymatically similar to prostatic secretions
What neural activity brings about the male and female resolution phase?
Activation of thoracolumbar sympathetic pathway
What are the effects in the vasculature of the resolution phase of coitus?
Contraction of arteriolar smooth muscle and increase venous return
What are the results of the male resolution phase?
Detumescence, flaccidity, refractory period, testes descend and scrotum wrinkles
What are the results of the female resolution phase?
Clitoris descends, labia regress and vagina shortens and narrows
What is the oust common cause of sexual dysfunction and has an increasing incidence?
Desire
What two categories can sexual dysfunction due to desire be divided into?
Hypo- and hyperactive
Describe sexual dysfunction due to hypoactive desire.
Little or no interest in sex, can lead to revulsion or fear of one or all aspects of process
What is hypoactive desire in sexual dysfunction often a result of?
Abuse or assault
How does the severity of sexual dysfunction due to hyperactive desire vary?
From abnormally high interest in sex to nymphomaniac
What is Klüver Bucci syndrome?
Pts with bilateral medial temporal lobe lesions from trauma, metastases etc display hyperphagia, hypersexuality, hyperorality, visual agnosia and docility
What changes due to female ageing can lead to reports of desire and arousal?
Decreased vasocongestion, loss of vaginal and urethral elasticity, decreased length and width of vagina, fewer orgasmic contractions and more rapid resolution
How does decreased vasocongestion cause a reduction in desire and arousal?
Loss of vaginal lubrication
What is the normal number of sperm in 2-4 ml of semen?
20-200 X 10^6 per ml
What proportion of sperm in 2-4 ml swim forward vigorously?
> 60%
What usually happens to semen within an hour of expulsion?
Become gelatinous and reliquefy
What proportion of the ejaculate do the seminal vesicles secrete?
60%
What is semenogelin?
Clotting factor released by the seminal vesicles
What are the components of the seminal vesicle fluid part of ejaculate?
Alkaline fluid, fructose, prostaglandins, clotting factors
What is the function of prostaglandins from seminal vesicle secretions?
Increase spermatozoa motility and increase female genital smooth muscle contraction
What proportion of the ejaculate is formed by prostatic secretions?
25%
What are the components of the prostatic secretions in the ejaculatory fluid?
Milky acidic fluid, proteolytic enzymes citric acid, acid phosphatase
What is the purpose of proteolytic enzymes from the prostatic secretions?
Re-liquefaction of semen
What is the citric acid found in prostatic secretions contributing to ejaculatory fluid used for?
Krebs cycle
What proportion of the ejaculatory fluid is due to bulbourethral gland secretions?
5%
What abnormal morphology can sperm display?
Giant, macro, double headed, double tailed, long head, rough head or abnormal mid-piece
What is the problem in sexual dysfunction to to female sexual arousal?
Persistent recurrent inability to lubricate in response to swelling
What is sexual dysfunction due to male arousal called?
Impotence
What is the most common cause of impotence?
Psychological due to descending inhibition of spinal reflexes due to cortical control
What are the physical origins of impotence?
Tear in fibrous tissue of corpus cavernosa, atherosclerosis, diabetes, alcohol, beta-blockers, diuretics
How does Viagra treat impotence?
Inhibit cGMP breakdown therefore increasing NO action
What are the 8 stages of fertilisation?
Semen deposition and transport; spermatid penetration of oocyte; block to polyspermy; syngomy; cleavage; compaction; hatching; implantation
When must semen deposition be timed so that fertilisation occurs?
Needs to be 3-0 days prior to ovulation
Why must the deposition of sperm be relatively tightly timed?
Sperm can survive up to 5 days but the oocyte is phagocytosed within 6-24 hours
When is the fertile time of the menstrual cycle?
Days 11.5-16
What happens to the oocyte upon fertilisation?
Takes 3-4 days to travel from ovary to body of uterus
What does failure of the fertilised oocyte to travel to the uterus cause?
Ectopic pregnancy leading to a non-viable embryo
How many spermatid reach the site of fertilisation in the female repro tract?
300
What is the action of oxytocin on the uterine body?
Stimulates uterine contraction
Where is semen deposited in the female repro tract?
Junction of vagina and cervix
How does the cervical mucus appear when oestrogen only is present?
Abundant and non-viscous
How does the cervical mucus appear when oestrogen and progesterone are acting?
Thick, sticky plug
What is the function of the oestrogen and progesterone stimulated cervical mucus?
Protects conceptus from infection
How many sperm are sacrificed to disperse the zona pellucida?
299
What does the sperm need to penetrate to facilitate fertilisation?
Corona radiata and zona pellucida
What is the corona radiata?
Layer of follicular cells around oocyte
What allows binding of sperm to ZP3 proteins on the oocyte?
Exposure to female repro tract removing seminal plasma coatings and some spermatid surface molecules exposing proteins
What does binding of sperm to ZP3 cause?
Acrosome reaction
What happens in the acrosome reaction?
Intracellular calcium signalling causes acrosomal enzymes to digest the zona pellucida
Where on the oocyte does the sperm bind?
Region rich in microvilli not region over metaphase chromosomes
When does the oocyte become a zygote?
Once the sperm has moved into the cytoplasm
How does sperm tail movement change during penetration of the oocyte?
Changes from beat to whip-like action
What are the two blocks to polyspermy and how do they differ?
Fast (temporary) and slow (permanent)
What happens in the fast block to polyspermy?
Electrical change to oocyte RMP from -75 mV to +20 mV due to sodium channel opening
Where does the wave of depolarisation in fast block polyspermy start?
Site of sperm entry
What happens in the slow block to polyspermy?
Calcium from ER causes wave of granule exocytosis
Why does granule exocytosis occur in a wave in the slow block to polyspermy?
Enzymes released stimulate adjacent granules
What does the cortical matrix modify?
Existing extracellular matrix
What is syngomy?
Union of male and female pronuclei to form diploid zygote
What happens to the oocyte during syngomy?
Completes meiosis II and expels second polar body
What happens during the cleavage stage of fertilisation?
Rapid mitotic divisions and metabolic changes amusing increasing number but not size of cells
What happens if two separate cell masses develop during cleavage?
Monozygotic twins
Why does the size of cells not increase in cleavage?
No new cytoplasm or organelles are formed
Why does each cell during cleavage have to be totipotent?
Needed to increase nuclear/cytoplasm ratio as one cannot transcribe enough RNA
How can the division in cleavage be described?
Asynchronous
When does compaction occur?
8-cell stage
What happens during compaction?
Polarisation and tight junction formation to crest inner embryo environment
What happens during hatching in fertilisation?
Enzymes from trophoblast cells digest ZP opposite to inner cell mass
Why is the ZP opposite the inner cell mass digested in hatching?
Reduce risk of enzymatic damage to embryo
What happens to the conceptus between ovulation and implantation?
Nourishment in intrauterine fluid for 2-3 days
When does implantation occur with respect to ovulation?
6 days later
What allows the trophoblast overlying the inner-cell mass to adhere to the progesterone primed endometrium in implantation?
It is sticky
Does the blastocyst display totipotency?
No
What is polyploidy?
3 or more pronuclei due to polyspermy or failure of second polar body extrusion
How long does it take for the zygote to become a blastocyst?
7 days (days 14-21)
What are the 3 methods of ‘natural’ contraception?
Abstinence, coitus interruptus, rhythm methods
Why is pt education needed in coitus interruptus?
Need to know sperm is present in pre-ejaculate
What does the rhythm method of contraception require?
Regular cycle
If a regular mestrual cycle lasts 28 days, when is the fertile period?
Days 7-16
What is vasectomy?
Bilateral split of vas deferens to prevent spermatid entering ejaculate
Is coitus affected by vasectomy?
No
Can vasectomy be reversed?
Yes
Why must the ejaculate be tested before relying on vasectomy for contraception?
Risk of residual sperm in ligated vas deferens
What are the 3 barrier methods of contraception?
Condoms, diaphragm and cap
What is used in addition to barrier methods to make the most effective?
Spermicide
What additional advantage does condom use have other than contraception?
Protects against STDs
Describe how diaphragms are used in contraception.
Lies diagonally across cervix to hold sperm in acidic vagina to reduce survival time
Why does diaphragm use as a contraceptive require aureate fitting?
Does not occlude passage of sperm
How does a cap work as a contraceptive?
Physical barrier to sperm across the cervix
How can alteration of the cervical mucus be used as a contraceptive method?
Progesterone can be used to mediate the production of thick ‘hostile’ mucus to inhibit sperm passage
How can progesterone be administered as a contraceptive?
Combined OCP, depot progesterone, implant/pill
What methods can be used to prevent ovulation in contraception?
Combined OCP, depot progesterone or progesterone only implant/pill
How does the combined OCP prevent ovulation?
Oestrogen causes loss of mid-cycle +ve feedback so no LH surge. Together with progesterone causes -ve feedback on HPA axis to inhibit follicular development
How does depot progesterone prevent ovulation?
Given IM every 3 months causes -ve feedback of HPA axis
How long is the progesterone-only implant effective for?
5 years
What is the main mechanism by which progesterone only implant/pill prevents conception?
Alsatian of cervical mucus (may inhibit ovulation at low dose)
How does female sterilisation serve as a contraceptive?
Clips/rings/ligation used to occlude Fallopian tubes
What are the problems with using female sterilisation for contraception?
Not very reversible and may recanalise
How can implantation be inhibited as a method of contraception?
Hormones such as OCP, POP, depot, progesterone implant directly affect receptivity of endometrium and indirectly via absence of corpus luteum causing endometrial preparation
How does post-coital contraception work?
Combined high dose oestrogen and progesterone or progesterone only make lining unfavourable for implantation up to 72 hours after intercourse
Why is post-coital contraception most effective within 72 hours of intercourse?
Embryo stays in uterine tubes in this time
What are the problems associated with post-coital contraception?
May disrupt ovulation +/- luteal function impairment
How does an intrauterine copper device act as a contraceptive?
Interferes with endometrial enzymes and possibly sperm transport by inducing a foreign body reaction
Why does IUCD not lead to PID?
Copper is inert
Which IUD carries a slightly higher infection risk?
Copper
When is an IUCD used for contraception?
For pure contraception with normal menstruation
How does a progesterone IUD act as a contraceptive?
Interferes with implantation
What additional benefits can a progesterone IUD give with contraception?
Easing of fibroid and endometriosis symptoms
When is a progesterone IUD used [unlicensed] and why?
Menorrhagia as after a year of use periods are light/absent
What is there a risk of if fertilisation occurs despite POP use?
Ectopic pregnancy
Why is the efficacy of OCP, POP, implants and depot good for contraception?
Multi-action
What is the definition of infertility?
Failure to conceive within 1 year
What proportion of couples are affected by infertility?
~15%
How is infertility due to female, male and unexplained cause split?
20-25% male, 45-60% female, 20-30% unexplained
What is male primary infertility?
No children by any partner
What is primary female infertility?
No conception ever
What is secondary infertility?
Failure to conceive following previous pregnancy whether this pregnancy was successful or not
What are three female causes of infertility?
Coital problems, anovulation and tubal occlusion
How do coital problems cause infertility?
Spasms of vaginalis muscle make coitus painful/impossible
When is anovulation normal in female reproductive life?
At start and end
What can cause anovulation during reproductive life?
Weight loss, hyperprolactinaemia, exercise, stress, pituitary tumours, pituitary necrosis, ovarian failure, menopause, radio or chemotherapy, PCOS
What is Sheehan’s syndrome?
Hypopituitarism due to post-partum haemorrhage
How does PCOS cause anovulation?
Uncertain pathogenesis causes high androgens, raising LH/FSH ratio, causing insulin resistance and cyst formation
What are the treatment options for anovulation?
Anti-oestrogen, FSH, pulsatile GnRH agonists
How can anovulation be diagnosed?
Look at hormones and anti-Müllerian hormone for follicle number
How can tubal occlusion cause infertility?
Sterilisation or scarring prevents passage of conceptus
How is tubal occlusion diagnosed?
Hysterectosalpinography
What are the treatment options for tubal occlusion?
Reanastomosis or assisted contraception
How can abnormal/absent production arise?
Testicular disease causing abnormal production, infection or vasectomy causing obstruction of ducts, hypothalamic/pituitary dysfunction
How can infertility due to abnormal/absent production be identified?
Semen analysis shows motility +/- morphology will be low
Why does semen analysis require a period of abstinence and regular interval between analyses?
Spermatogenesis is cyclic
