Getting Preganant Flashcards
(24 cards)
At what point in their maturation can sperm move by themselves?
At the tail of the epididymis. They also have the potential to fertilise here.
What is maturation of sperm dependant on?
Support of the epididymis by androgens.
What is the purpose of semen?
Transport medium for sperm
Nutrition
Buffering capacity
Role for prostaglandins in stimulating muscular activity in the female tract
What is the composition of the seminal plasma?
Seminal vesicles - 60% - alkaline fluid (neutralises the acid: Male urethra and female reproductive tracts) , fuctose, prostaglandins, clotting factors (particularly semenogelin)
Prostate glands - 25% - milky, slightly acidic fluid. Contain proteolytic enzymes, citric acid, acid phosphotases
Bulbourethral / Cowper’s glands - Small volume - alkaline fluid containing a mucous that lubricates the end of the penis and urethral lining.
What are the four stages of the human sexual response?
Excitement phase (psychogenic / somatogenic stimuli)
Plateau phase
Orgasm phase
Resolution phase - males have a refractory period
How does errection occur?
Stimulants - Psychogenic or tactile (sensory afferents of the penis and perineum)
Spinal reflex
Efferents - Somatic and autonomic efferents, pelvic nerve (PNS), pudential nerve (somatic).
Causes heemodynamic changes
What happens in the penis to cause an errection?
Sinusoidal relaxation
Arterial dilation
Venous compression
The tunica albuginea encases the penis and creates the venous compression.
What are the nerves for the parasympathetic innervation of penis?
Fibres come from the lumbar and sacral spinal levels.
Pelvic nerve and pelvic plexus
Cavernous nerve to corpora and vasculature.
How does NO get released during an erection?
Inhibition of sympathetic vasoconstrictor nerves activate the PNS.
Activation of non-adrenergic, non cholinergenic, autonomic nerves to arteries releasing nitric oxide.
What is the role of NO in an erection?
Post-ganglionic release ACh
ACh bonds to M3 receptors on endothelial cells.
A rise in intracellular [Ca2+], activation of NOS and formation of NO
NO diffuses into vascular smooth muscle and causes relaxation (vasodilation)
NO also released directly from nerves
What can cause erectile dysfunction?
Psychological (descending inhibition of spinal reflexes)
Tears in fibrous tissue of corpora cavernosa
Vascular (arterial and venous)
Drugs
How does viagra work?
Slows rate at which cGMP is degraded
What happens in emission?
- Movement of semen into prostatic urethra
- Contraction of smooth muscle in prostate, vas deferens and Seminal vesicles.
How does ejaculation occur?
- Contraction of glands and ducts (smooth muscle)
- Bladder internal sphincter contracts To prevent retrograde ejaculation
- Rhythmic striatal muscle contractions (pelvic floor ad perineal muscle ischiocavernosus, bulbospongiosus)
How does the cervical mucus change over the menstrual cycle?
Oestrogen - think and stretchy (when fertile)
Oestrogen and progesterone - Thick, sticky, forms a plug. (Mechanical barrier to fertilisation)
What is capacitation?
This is further maturation of sperm in female reproductive tract - sperm cell membrane changes to allow fusion with oocyte cell surface and the tail movement changes from beat to whip like action.
The sperm can now undergo the acrosome reaction.
What is the fertile window? Why?
Sperm deposition up to 3 days prior to ovulation or day of ovulation.
This is because sperm live 48-72hrs whereas oocytes only live 6-24hrs.
Give an overview of the events of fertilisation.
Fertilisation normally occurs in the ampulla of the uterine tubes. It requires the loss of sperm outer shell (acrosome) then penetration of ovum membrane, fusion of ova and sperm membrane and eventual formation an fusion of pronuclei.
What is the acrosome?
It is derived form Golgi region of the developing spermatid. It contains enzymes and is necessary for fertilisation.
What is the acrosome reaction?
- Sperm pushes through corona radiata.
- Binding of sperm surface receptor to ZP3 glycoproteins of zone pellucida.
- Triggers acrosome reaction
- Digestion of zona pellucida.
How does the body make sure that only one sperm penetrates?
Cortical reaction - ca2+ released to make sure only one sperm can reach the oocyte nucleus
What is the morula?
A collection of totipotent cells produced just after fertilisation.
What happens in assisted reproductive technology?
Oocytes are fertilised in vitro and allowed to divide to the 4 or 8 cell stage.
The morula is then transferred to the uterus.
This can also be used for Pre-implantation Genetic Diaagnosis (PGD). This is when a cell is safely removed from the morula and tested for serious heritable conditions prior to transfer of the embryo into the mother.
How does implantation occur?
Outer cell mass (trophoblast) interacts with endometrium.
Endometrium controls degree of invasion.
But, ectopic can be dangerous…
No endometrium = invasion not controlled
Lower uterine = placenta previa
