Endocrinology of the Male Flashcards
Do males have a surge or tonic center? Why or why not?
Males only have a tonic center because estrogen defeminizes the surge center; the surge center is also not important to males, because it is only appropriate for the GnRH surge and driving the LH surge for CL formation, oocyte formation, etc. which is only needed in the female
What are the LH surge patterns in males?
LH surges with a subsequent surge of testosterone, which cycles and continues in this pattern
Is GnRH important for males?
yes. after binding the gonadatropins in the anterior pituitary, GnRH causes a release of both LH and FSH.
Importance of LH in males?
it causes testosterone production by the Leydig cells, which once produced is released into the general circulation and has a negative feedback at the level of the hypothalamus and pituitarty to control the amount of GnRH and LH that is released.
why is the negative feedback loop of testosterone important?
it regulates how much testosterone is being produced by those Leydig cells that are in the interstitial space in the testis
What is another function of testosterone for when it enters the ST?
it is important for sertoli cell function and for promoting the further development of those spermatagonial cells (early pre-sperm cells)
how is testosterone transported to the epididymis?
it gets into the lumen of the ST, binds with androgen binding protein which allows it to be transported to the epididymis and further needed to regulate the function of the epididymal cells
Why is FSH important?
from the anterior pituitary, it is important in terms of sertoli cells: binding receptor of sertoli cells, important for tight junctions to form between sertoli cells, forming a microenvironment important for spermatagenesis; causes production of inhibin by sertoli cells to regulate how much FSH is released by AP; sertoli cell produces ABP; binds testosterone in ST to take out and get it to epididymis; allows for production of estradiol
Where is testosterone produced in the female?
theca interna cells
Where is testosterone produced in the male?
Leydig cells, but then travels to the sertoli cells under the influence of FSH that testosterone is aromatized via the enzyme aromatase to estradiol
What does testosterone get aromatized to?
estradiol
What is produced under the influence of FSH?
inhibin which has a negative feedback at the AP where some estradiol has a negative feedback to AP and hypothalamus
What is the relationship between GnRH, LH, and FSH?
release of GnRH, shortly after, a release of LH which regulates FSH release (small peaks of FSH at high surge peaks of LH with small peaks of GnRH just before the LH surge and FSH peaks)
Which hormone plays a role in the release o testosterone from the Leydig cells?
LH (it surges and regulates the release of surges of testosterone
spermatogenesis?
the process of producing spermatazoa; sum of all cellular transformations in developing germ cells in ST
Where do spermatic cells progress in the ST as they increase in maturity?
the lumen
What shape are early sperm cells?
round
What will sperm cells closest to the lumen resemble?
sperm with head and tail unlike early sperm cells (round)
myoid cells?
muscle like cells that facilitate movement of sperm out of lumen of ST
What are the three phases of spermatogenesis?
Proliferation, meiosis, differentiation
proliferation phase?
starts with early primitive cells that undergo mitotic divisions (proliferation) and at some point they have to enter and complete meiosis to become the haploid gamete required to meet up with the oocyte; this is the time period where sperm cells undergo a series of mitotic divisions (spermatocytogenesis)
Meiosis phase?
time period after mitotic divisions stop and germ cells enter into meiosis and sperm (once they start) complete it - unlike oocytes
differentiation phase?
round cells undergo a metamorphasis and become like the cell type (easily identifiable) that has an elongated head and a tail (spermiogenesis)
spermatocytogenesis?
time period where early spermatagonia goes from this stage up to the primary spermatocyte; stage capable of initiating meiosis
Are mitotic divisions species specific?
yes, usually between 2-6 divisions with potential daughter cells ranging from 4-64
what are spermatic cells are connected by?
cytoplasmic bridges with allow the cells to communicate and ensures that the sex ratio remains around 51% males, 49% females