Male reproductive physiology

Question 1

what week are the gonads indiffirent?

Answer 1

until 5 week

Question 2

what does the y chromosome contain?

Answer 2

contains SRY gene

Question 3

what does SRY do?

Answer 3

it encodes transcription factor called TDF ( testis determination factor)

Question 4

what does TDF do?

Answer 4

Induces transcroíption of Sry and Sf1 which in turn induces transcription of SOX9

Question 5

What does SOX9 induce?

Answer 5

• causes gonad–>testis

- inhibits b-catenin ( hormone for female development)

Question 6

What happens when Y-chormosome isn´t present?

Answer 6

Wnt4 stimulates b-catenin, whichin turn inhbits SOX9, so gonad–> ovary

Question 7

how´s the secreation of GnRH from child–>puberty?

Answer 7

Low until puberty, then it becomes pulsatile.

Question 8

why is it important that the secreation is pulsatile?

Answer 8

Needed for the for receptor sensitivity that allows normal reproductive hormone levels.
if they are continues the receptors loose the sensitivity.

Question 9

what are the two peaks of testosterone secreation before puberty?

Answer 9

• First for genital development

- 2nd for developent of male-type CNS

Question 10

what inhihits the arcuate nucleus?

Answer 10

E2

Question 11

does testosterone inhibit arcuate nucleus?

Answer 11

No, the arcuate nucleus expresses armotase which converts testosterone–> E2

Question 12

what limits the FSH production?

Answer 12

Inhibin and E2, produced by sertoli cells

Question 13

what inhibits LH?

Answer 13

testosterone and dihydrotestosterone

Question 14

what stimulates arcuate nucleus?

Answer 14

-ligt
-stress
- emotional stimuli
- insulin
- glucose
leptin

Question 15

location of spermatogenesis?

Answer 15

the testis

Question 16

what does sertoli cells do?

Answer 16

• provide nutrients
• secreate fluid for transport sperm
• create blood-testis barrier

Question 17

what does blood testis barrier do?

Answer 17

via tight junctions make an immunological privelaged site, prevents immune system from attacking the developing germ cells

Question 18

whats spc with the tight junctions of the sertoli cells?

Answer 18

• make an apical and basalcompartment

- the basal is accesible to the immune system, but apical isn´t

Question 19

componets secreated by sertoli cells?

Answer 19

• estrogen
• inhibin
• ABG (androgen binding protein)
• ICAM

Question 20

function of ABG?

Answer 20

binds free testosterone in the seminiferous tubules to provide adequate nutrition to the developing sperm cells.

Question 21

function of ICAM?

Answer 21

binds sperm cells to the sertoli cells during their maturation

Question 22

what enzymes does the testis lack, so they cant syntesize gluco and minerlcorticoids?

Answer 22

• 21-b-ohlase

- 11-b-ohlase

Question 23

what enzyme forms testosterone from androstenedione?

Answer 23

17-b-HSD

Question 24

what enzyme forms the dihydrotestosterone?

Answer 24

5-a-reductase

Question 25

whats the ratel.limiting step in testosterone synthesis?

Answer 25

conversion of chol–>pregnenolone by p450scc (desomlase)

Question 26

how much of testosterone is free, bounded to proteins?

Answer 26

• 70-80 % bounded to sex steroid binding protein(SHBG)
• 20% bounded to albumin
• 1-3% is free

Question 27

when is testosterone secreated in women?

Answer 27

when women is fertile, during her ovaroan cycle

Question 28

process of spermatogenesis?

Answer 28

1. spermatogonia (primordial germ cell)–>mitosis
   - this gives either more spermatogonia or primary spermatocyte.
2. primary spermatocyte–>meiosis 1–> 2 second spermatocyte
3. 2 2nd spermatocyte–> meiosis 2–> 4 haploid spermatids.

Question 29

explain maturation process of the sperm?

Answer 29

• 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.

Question 30

components necessary for spermatogenesis?

Answer 30

• testosterone
• androgen binding protein
• estrogen
• inhibin
• GFs
• ICAM
• vitamins: a,b,d,e
• temp 30-32

Question 31

what are the effects of DHT?

Answer 31

• external male genitalia

- prostategrowth

Question 32

composition of semen?

Answer 32

• 10% sperm cell

- 90% seminal fluid

Question 33

composition of seminal fluid?

Answer 33

• 60-70% fructose, fibrinogen, prostaglandins

- 25-30% prostatic specific antigen, zinc, fibrinolysin

Question 34

process of erection?

Answer 34

• parasympathetic process–>reduction of alpa-1-R–> vasodilation in arterioles–>blood goes through capillary systet–> tissue swells

Question 35

mechanism of erection?

Answer 35

1. endothelial NO is released–> cGMP activation–> PKG–>calcium pumps increase–> calcium channel decreased–> Low Ca2+ concentration.

Question 36

effect of parasym?

Answer 36

• activation of VIP
• Inhibition of PLC
• Low CA2+ concentration

Question 37

Name an anti-erection agent and what is it inhibited by?

Answer 37

phosphodiesterase type 5, inhibited by sildenafil (viagra)

Question 38

process of ejaculation?

Answer 38

• 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)

Question 39

why is BP and HR increased during ejaculation?

Answer 39

b/c the sympathetic avtivity is not only local

Question 40

name causes to erectile dysfunction?

Answer 40

• type 2 diabetes
• smoking
• stress
• hypergonadism
• arteriovenosus malformation