Male Repro Flashcards
How does LH in males stimulate testosterone synthesis?
Gs coupled receptor that stimulates transcription of genes for 17 beta hydroxysteroid dehydrogenase
What does P-450 aromatase do in males?
Convert testosterone to estradiol to support spermatogenesis
What does FSH on sertoli cells stimulate?
- ABP
- P-450 aromatase
- 5a-reductase
- Growth factors
- Inhibins
- Activins
What is the carrier protein of androgens in the seminiferous tubule lumen?
Androgen-binding protein
What are the androgen systemic effects?
- Masculization during development
- Growth on skeletal muscle (anabolic steroid)
- Inhibit adipose deposition
- CNS effect increase aggression and libido
What do androgens bind to?
Androgens receptors that are bound to Hsp90
What is the role of androgens in repro?
Support spermatogenesis
What happens to the hormones when a male is castrated?
An excess of FSH and LH because there is no target. This turns off GnRH from the pituitary
The first division in spermatogenesis is…
Mitotic division to make a type A and type B cell
What is the second division in spermatogenesis…
Type B cells divide mitotically several times before meiosis. They are now primary spermatocytes
What is spermiogenesis?
Series of functional and morphological changes to produce spermatozoa
What are important changes in spermiogenesis?
- Flagellum
- Mitochondrial midpiece for energy for motility
- Acrosome cap important for fertilization
- Condensation of the nucleus and disulfide crosslinking of DNA for protection
- Remove excess cytoplasm
What do sertoli cells do?
-Respond to FSH and promote proliferation of spermatogoneia
-Make 5a reductase
-Secrete ABP
=Secrete inhibin for feedback
-Gap junction communicate with spermatozoa
-Phagocytose residual body
- Blood testis barrier so sperm not killed
Is number of spermatogonia going through spermatogenesis hormone dependent?
No. Hormones will not increase spermatogenesis
What determines the number of spermatogonia going through spermatogenesis?
Number of Sertoli cells ( the more the merrier)
How do male hormones sustain spermatogenesis?
They secrete survival factors to sertoli cells with communicate this to the spermatids which otherwise have high levels of Bax/Bac which would push it towards apoptosis
How can you measure daily sperm production?
Measuring testicular size
- number of sertoli cells
- number of spermatozoa
What temperature is optimal for sperm development?
2-4 degrees celsius below body temperature (why they external to body)
How do the scrotum thermoregulate?
- Acts as a thermosensor and causes feedback to hypothalamus changing behavior (sweat, panting etc)
- Counter-current heat exchange from pampiniform plexus
What is the pampiniform plexus?
Artery with a bunch of veins around it to exchange heat
What is the third division of spermatogonia?
Asymmetric meiosis generating secondary spermatocytes
What is the fourth division of Spermatogenesis?
Meiosis II. Secondary spermatocytes become spermatids
What is the end result of spermatogenesis?
Spermatids that are haploid
How much sperm is produced daily?
Millions of sperm are made but only about 1/2 survive
