w5 Male Endocrinology & Spermatogenesis Flashcards
5 Male endcrinolog parts
Testes Hypothalamus Pituitarty Leydig cells Sertoli Cells
Endocrine requirements before spermatozoa can be produced
Adequate GnRH released from Hypothalamus (frequent intermident episodes for a few mins then LH secretion occurs soon after
FSH and LH secreted from anterior lobe of pituitary
(LH 10 mins and occurs 4-8 times a day. FSH pulses are lower but longer duration due to release of inhibin)
Secretions of gonadal steroids - testosterone and estradoil
What does LH act on in testes
LH receptor on cell membrane
Leydig cell synthesise progesterone and convert this to testosterone
Testosterone released in pulsatile manner = high conc. for short periods of time,
Testosterone pulse, 30mins after LH pulse
Testicular function dependent on
GnRH secretions every 3-6hrs
High conc of testosterone in seminiferous tubule
Low conc of testosterone in systemis blood
adequate LH receptors in Leydig cells
leydig cells equivalent to
Theca interna cells
Sertoli cells equivalent to
follicular granulosal cells
Sertoli cell function
Convert testosterone to estradoil
Secrete inhibin that exerts negative feedback on pituitary, suppressing FSH secrection
Testosterone and E2 have negative feedback on hypothalamus, therefore preventing LH and FSH secretaion
Spermatogenesis
proliferation + meiosis + differentiation
Where does spermatogenesis take place
Seminiferous tubules
3 phases of spermatogenesis
proliferation phase (mitotic divisions)
Meiotic phase
(primary spermatocytes to spermadits)
Differentiation phases (spermiogenesis) get head, tail etc
Proliferation phase
Generations of A spermatogonia undergo mitotic divisions generating large number of b spermatogonia
Stem cell renewal
Meiotic phase
Primary spermatocytes to secondary spermatocytes through meiosis buy crosing over occurs = no 2 sperm are identical
Differentiation phase (spermiogenesis)
No further cell divisions and get head, flagellum and midpiece
4 phases of Differentiation phase / spermiogenesis
Golgi
Cap
Acrosome
Maturation
Cycle of seminiferous epithelium
Progression through a complete series of cellullar associations (stages) at one location alone seminiferous tubules
