Male reproductive physiology Flashcards
what week are the gonads indiffirent?
until 5 week
what does the y chromosome contain?
contains SRY gene
what does SRY do?
it encodes transcription factor called TDF ( testis determination factor)
what does TDF do?
Induces transcroíption of Sry and Sf1 which in turn induces transcription of SOX9
What does SOX9 induce?
- causes gonad–>testis
- inhibits b-catenin ( hormone for female development)
What happens when Y-chormosome isn´t present?
Wnt4 stimulates b-catenin, whichin turn inhbits SOX9, so gonad–> ovary
how´s the secreation of GnRH from child–>puberty?
Low until puberty, then it becomes pulsatile.
why is it important that the secreation is pulsatile?
Needed for the for receptor sensitivity that allows normal reproductive hormone levels.
if they are continues the receptors loose the sensitivity.
what are the two peaks of testosterone secreation before puberty?
- First for genital development
- 2nd for developent of male-type CNS
what inhihits the arcuate nucleus?
E2
does testosterone inhibit arcuate nucleus?
No, the arcuate nucleus expresses armotase which converts testosterone–> E2
what limits the FSH production?
Inhibin and E2, produced by sertoli cells
what inhibits LH?
testosterone and dihydrotestosterone
what stimulates arcuate nucleus?
-ligt
-stress
- emotional stimuli
- insulin
- glucose
leptin
location of spermatogenesis?
the testis
what does sertoli cells do?
- provide nutrients
- secreate fluid for transport sperm
- create blood-testis barrier
what does blood testis barrier do?
via tight junctions make an immunological privelaged site, prevents immune system from attacking the developing germ cells
whats spc with the tight junctions of the sertoli cells?
- make an apical and basalcompartment
- the basal is accesible to the immune system, but apical isn´t
componets secreated by sertoli cells?
- estrogen
- inhibin
- ABG (androgen binding protein)
- ICAM
function of ABG?
binds free testosterone in the seminiferous tubules to provide adequate nutrition to the developing sperm cells.
function of ICAM?
binds sperm cells to the sertoli cells during their maturation
what enzymes does the testis lack, so they cant syntesize gluco and minerlcorticoids?
- 21-b-ohlase
- 11-b-ohlase
what enzyme forms testosterone from androstenedione?
17-b-HSD
what enzyme forms the dihydrotestosterone?
5-a-reductase
whats the ratel.limiting step in testosterone synthesis?
conversion of chol–>pregnenolone by p450scc (desomlase)
how much of testosterone is free, bounded to proteins?
- 70-80 % bounded to sex steroid binding protein(SHBG)
- 20% bounded to albumin
- 1-3% is free
when is testosterone secreated in women?
when women is fertile, during her ovaroan cycle
process of spermatogenesis?
- spermatogonia (primordial germ cell)–>mitosis
- this gives either more spermatogonia or primary spermatocyte. - primary spermatocyte–>meiosis 1–> 2 second spermatocyte
- 2 2nd spermatocyte–> meiosis 2–> 4 haploid spermatids.
explain maturation process of the sperm?
- When they have finiched meiosis 2 they are still, immature and not motile.
- overall process takes 74 days
- they move from seminiferous tubules to head of epididymis, and then to tailwhich takes 10-15 days, where they mature.
they are not compleatly active b/c pH is too low. compleate activation occurs in female genital tract.
A process called capacitation.
components necessary for spermatogenesis?
- testosterone
- androgen binding protein
- estrogen
- inhibin
- GFs
- ICAM
- vitamins: a,b,d,e
- temp 30-32
what are the effects of DHT?
- external male genitalia
- prostategrowth
composition of semen?
- 10% sperm cell
- 90% seminal fluid
composition of seminal fluid?
- 60-70% fructose, fibrinogen, prostaglandins
- 25-30% prostatic specific antigen, zinc, fibrinolysin
process of erection?
- parasympathetic process–>reduction of alpa-1-R–> vasodilation in arterioles–>blood goes through capillary systet–> tissue swells
mechanism of erection?
- endothelial NO is released–> cGMP activation–> PKG–>calcium pumps increase–> calcium channel decreased–> Low Ca2+ concentration.
effect of parasym?
- activation of VIP
- Inhibition of PLC
- Low CA2+ concentration
Name an anti-erection agent and what is it inhibited by?
phosphodiesterase type 5, inhibited by sildenafil (viagra)
process of ejaculation?
- sympathetic process
- contraction of vas deferens, accesory glands, inner urinary sphincter, urinary
- relaxation of outer urinary sphincter
expulsion requires relaxation of external urethral spinhcter ( somatic control) and contraction of inne (autonomic control)
why is BP and HR increased during ejaculation?
b/c the sympathetic avtivity is not only local
name causes to erectile dysfunction?
- type 2 diabetes
- smoking
- stress
- hypergonadism
- arteriovenosus malformation
