Getting Pregnant - Sex And Fertilisation Flashcards
What does coitus mean?
Sex
When do spermatozoa become cable of movement?
Once at the tail of the epididymis
Support of epididymis by androgens allows maturation - addition of secretory products to surface of sperm so capable to fertilise
What is semen made up of?
Spermatozoa and seminal plasma (from accessory glands)
What’s the functions of seminal plasma?
Transport medium
Nutrition
Buffering capacity (female tract acidic)
Role for prostaglandins in stimulating muscular activity in female tract
What glands contribute to seminal plasma, what do they add and by what percentage?
Accessory glands:
- seminal vesicles 60% Alkaline fluid (neutralise acid in Male & fm reproductive tracts), fructose (metabolite), prostaglandins, clotting factors e.g. semenogelin (so not immediately lost)
- prostate gland 25%
Milk, slightly acidic fluid, proteolytic enzymes (breakdown clotting proteins mobility), citric acid, acid phosphotase
-bulbourethral glands (Cowper’s) <1%
Alkaline fluid, mucous lubricants end of penis and urethral lining
Where does fertilisation normally take place?
Ampulla of uterine tube
What are the 4 stages of the human sexual response?
Excitement - psychogenic/ somatogenic stimuli
Plateau
Orgasm
resolution (return to haemodynamic norm followed by refractory period in males)
What are the three stages of the Male sexual response?
Erection
Emission & ejaculation
Ejaculation
What are the stimulants and efferents involved in an erection what do they lead to?
Stimulants:
- Psychogenic
- Tactile (sensory afferents of penis and perineum)
Efferents:
Somatic and autonomic
- pelvic nerve (PNS)
-pudendal nerve (somatic)
-> haemodynamic changes
What is the erectile tissue of the penis? What veins and arteries surround/ are within these tissues?
Corpus spongiosum & 2 corpus cavernosum
Superior to inferior: Superficial dorsal v a Deep dorsal v a Efferent v Cavernous v Emissary v Cavernous a Bulbourethral v Urethral a
What does an erection require after stimulation?
Sinusoidal relaxation
Arterial dilation
Venous compression
What is the parasympathetic innervation to the penis? What does stimulation of these nerves cause the release of?
Lumbar and sacral spinal levels
- Pelvic nerve and pelvic plexus
- Cavernous Nerve to corpora and vasculature
Erection: inhibition of sympathetic arterial vasoconstrictors nerves, activation of PNS (non-adrenergic, non-cholinergic autonomic nerves to arteries) -> NO
What role does NO have in causing an erection? E.g. how is it released and what does it do?
Post- ganglionic fibres reales ACh -> binds to M3 receptor on endothelial cells -> rise in Ca2+ -> activates NOS -> No formed -> diffuses into vascular SM -> vasodilation
NO also released directly from nerves
What can causes erectile dysfunction?
Psychological (descending inhibition of spinal reflexes)
Tears in fibrous tissue of corpora cavernous
Vascular problems e.g. micovascular diabetes
Drugs
How does viagra work?
Slows rate at which cGMP is degraded (NO causes GTP to become cGMP which then -> PKG and causes vasodilation/ erection)
PDE V converts cGMP to an inactive product so viagra e.g. sildenafil inhibits this
What is emission and what controls it?
Emission is movement of semen into prostatic urethra (contraction of SM in prostate, vas deferens and seminal vesicles)
Under sympathetic control
What is ejaculation and what controls it?
Expulsion of semen
Contraction of:
glands and ducts SM
Bladder internal sphincter
Rhythmic striata muscle (pelvic floor, perineal muscles: ischiocavernosus and bulbospongiosus)
Under sympathetic control
How does cervical mucus change over the course of the menstrual cycle?
When just oestrogen is present mucus is thin and stretch in preparation for ovulation so sperm can move easily in
When oestrogen and progesterone are present mucus forms a thick, sticky plug which prevents access for further gametes and protects the cervix from outside in case of pregnancy
What is the fern test?
Testsfor fern like patterns of cervical mucus which could indicate leakage of amniotic fluid in pregnancy
What is spinnbarkeit?
Or fibrosity
The stretchiness/ stringiness of a substance e.g. cervical mucus
Where is sperm deposited in the urethral?
In the external Os
What is capacitation? how long does it take, where and what occurs?
Further maturation of sperm in female reproductive tract (6-8hrs)
Sperm cell membrane changes to allow fusion with oocyte cell surface
Tail movement changes from beat to whip-like action (for the head to enter the zona pellucida)
Now capable of undergoing the acrosome reaction
What’s the fertile window for oocytes and spermatozoa once in female tract?
Oocytes - 6-24hrs
Spermatozoa - 48-72 hrs
Fertile period: 3 days prior to ovulation or day of
How do both gametes get transported?
Oocyte - beating cilia and peristalsis of uterine tube
Sperm- own propulsion flagella
What triggers and occurs in the acrosome reaction?
Sperm pushes through corona radiate -> sperm surface receptor binds to ZP3 glycoprotein of zona pellucida -> acrosome reaction (digestion of zona pellucida)
What blocks polyspermy?
Once sperm penetrates -> fusion of plasma membranes (cortical reaction) blocks more sperm penetrating
What triggers meiosis 2 to occur in ococytes?
Fusion of occyte and sperm membranes -> calcium waves activated -> meiosis 2 occurs -> pronuclei mkve together -> mitotic spindle forms -> cleavage
What’s a morula?
4-8 cells
Each cell = totipotent
How does in-vitro fertilisation work? what’s PGD?
Oocytes are fertilised in vitro and allowed to divide to 4-8 stage (morula) transferred to uterus
Morula testes for heritable conditions prior to transfer of embryo - pre- implantation genetic diagnosis
What does the morula become and what then happens before implantation?
Blastocyst
Hatched from zona pellucida
Now free to enlarge
Interacts with uterine surface to implant
What layers make up a blastocyst?
Zona pellucida
Trophoblast
Blastocoel
Embryoblast
When does implantation occur in relation to ovulation? What can you get if implantation happens outside the endometrium or in a lower uterine segment?
9-10 days post-ovulation
Outer cell mass (trophoblast) of blastocyst interacts with endometrium
Can get ectopic implantation/ placenta praevia
