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VIII. Adult Male back to VIII. Adult Female A. Reproductive Anatomy 1. Testes a. Seminiferous tubules i. where spermatogenesis & spermiogenesis take place ii. coiled loops b. Lobule i. 250/testis; 1-3 closed coiled loops/lobule c. Tubulus Rectus d. Rete Testis e.Vasa Efferentia 2. Epididymis a. Site of Sperm Storage b. Head c. Body d. Tail i. Ductus Epididymis 3. Vas Deferens a. transport of ejaculate B. Seminiferous Tubule Function 1. Interstitium a. Leydig Cells i. synthesize steroid hormones (D5(similar)) (1) Major: Testosterone (T) (2) Other: Androstenedione, DHEA, 5a-DHT (5a-Dihydrotestosterone) (a) also very small amounts of estradiol ii. homologous to theca b. blood vessels & connective tissue 2. Seminiferous Epithelium a. Spermatogonia produced throughout life i. 2N, mitosis b. 1o Spermatocytes (2N) i. Meiosis I c. 2o Spermatocytes (N) i. Meiosis II d. Spermatid (N) e. Spermatozoa i. Sertoli Cells (1) provide nutrients for spermatozoa, secrete ABP (androgen binding protein), phagocytosis of degenerated germ cells (2) produce testicular fluid ® into lumen (3) homologous to granulosa cells 3. Spermatogenesis: a ® d a. making of spermatogonia ® spermatids 4. Spermiogenesis: d ® e a. spermatid to spermatozoa 5. Spermiation a. sperm being released from sertoli cell into lumen
PROCESS |
STRUCTURE |
HORMONE NECESSARY |
| Spermatogonia | ||
| mitosis | ¯ | FSH and/or T |
| Spermatogonia | ||
| Meiosis I
Spermatogenesis |
¯ | ? |
| 1o Spermatocytes | ||
| Meiosis I
Spermatogenesis |
¯ | T |
| 2o Spermatocytes | ||
| Meiosis II
Spermatogenesis |
¯ | T |
| Spermatid (N) | ||
| Spermiogenesis | ¯ | FSH |
| Spermatozoa (N) | ||
| Spermiation | ¯ | LH (just like ovulation) |
| released Spermatozoa (N) |
C. Gonadal Axis regulation
1. GnRH (pulsatile) ® LH (pulsatile) ® T
a. GnRH stimulates the release of both LH and FSH
i. pulsatile GnRH release necessary
for gonadotropin secretion
b. pulsatility maintains [GnRH-R]
c. autopriming: LH/FSH release 4-6x higher
on 2nd dose (pulse) of GnRH
2. mechanism of pulsatile GnRH release
a. GnRH neurons have intrinsic oscillatory capacity
i. may be enhanced or paced by extra-ARC transmitters
(1) NE, NPY, GABA
pulse synchronously with GnRH
(a) NPY + GABA are transmitters
used for timing by SCN
b. GnRH 2nd messengers are Gs ® AC ® cAMP or
IP3 ® Ca++ ® calmodulin
c. autocrine +feedback control
i. pacemaker ® V gated Ca++ ®+ exocytosis ®+ GnRH
ii. GnRH ®+ GnRH-R (autoreceptors) ®+ IP3/Ca++
(1) Ca++ ®+ NOS ®+ NO ®+ (more) GnRH
iii. ultrashort negfeedback inhibits spontaneous pulsatility
during 2nd phase (habituation of autoreceptor action?)
3. T feeds back to regulate GnRH and LH levels
a. binds to androgen binding proteins (SBP) in the blood
b. manner of feedback determines manner of release
i. + vs -
modified by activin, inhibin, leptin, galanin
4. Inhibin/Activin
a. small polypeptides
b. made in Sertoli cells
c. feeds back to regulate FSH levels
i. selectively inhibits (inhibin)
or stimulates (activin) FSH
d. also found in Antral fluid of females
4. Leptin
a. produced by adipose (fat) cells
b. stimulates GnRH by binding to ob/obb-R
5. galanin (Gal)
a. colocalized in GnRH neurons,
and stimulates GnRH release (with NPY)
b. released with GnRH,
also stimulates LH (but not FSH)
D. Androgen Target Cells
1. Secondary Sex Characteristics
(facial hair, rooster comb, phallus development)
5a-reductase
a. T --------® 5a-DHT
i. intracellular conversion
b. DHT binds to cytoplasmic/nuclear receptors (A-R)
2. muscle has no 5a-reductase
a. although A-R has a higher affinity for 5a-DHT,
T may bind when concentrations are high enough
3. Brain (and other adipose tissue)
aromatase
a. T -------® E2
i. bind to E-R
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