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
meiosis?
production of haploid gametes beginning with the spermatocytes and ending with round spermatids
Difference between meiosis in males and females?
in males, meiosis doesn’t stop, it gets completed. In females, it stops twice
Where does DNA synthesis occur in meiosis?
the S phase
What cell types are present in the gap phase?
primary spermatocytes and primary oocytes (diploid cells)
At what point do the diploid cells each split into two copies to where the cell is 4N?
s phase
Before entering DNA synthesis, cells switch from __ to __.
mitosis to meiosis
5 phases of prophase in meiosis?
leptotene, zygotene, pachytene, deplotene/dictyate, diakinesis
leptotene phase?
chromosomes condense 1st phase
zygotene?
homologous chromosomes begin to pair: phase 2
pachytene?
pairing is completed; crossing over of homologues (recombination): phase 3
diplotene/dictyate?
homologous chromosomes pull apart but remain attached at crossover points (chiasma), RNA synthesis is possible, oocytes arrest here until LH surge or other stimulus initiates resumption of meiosis phase 4
diakinesis?
transition to metaphase; chromosomes recondense, RNA synthesis stops, not as distinct in males: phase 5
Metaphase I?
homologous chromosomes move toward opposite poles and pair across from one another, homologous chromosome held together by chiasma
Anaphase I?
begin to pull apart and are different from before as a result of recombination of crossing over
Telophase I?
(cytokinesis); secondary spermatocyte; in oocyte extruded as polar body (only 1 copy of chromosomes), but in males you get two cells that look the same (with 2 copies of chromosomes)
Metaphase II?
secondary spermatocytes formed (oocytes stop here until fertilized but sperm continues)
Anaphase II?
completion of meiosis
end result of meiosis?
fours cells from the first one that entered with each having a unique set of chromosomes
All phases of meiosis in order?
prophase, metaphase I, anaphase I, telophase, metaphase II, anaphase II
spermatogenesis vs oogenesis?
each has a unique set of chromosomes that can contribute to the genome of the zygote, assuming it gets fertilized; the oocyte while it is sitting to be fertilized has two and it doesn’t become haploid until after fertilized by the sperm and a series of things occurs for it to get rid of the second polar body
spermiogenesis?
round spermatids are transformed to spermatozoa in four phases
What are the four phases of spermiogenesis (differentiation)?
golgi, cap, acrosomal, maturation
What three things occur during spermiogenesis?
nucleus becomes highly condensed, acrosome forms, cells become potentially motile (tail forms and acquire of metabolic power plant which provides fuel for driving and allowing motility
golgi phase?
acrosome development, migration of centrioles; small golgi vesicles fuse giving rise to larger secretory proacrosomic granules; proximal and distal centrioles migrated which gives rise to the tail (flagellum)
Function of proximal centriole?
allows flagellum to be anchored to the nucleus
Function of distal centriole?
gives rise to developing axoneme (central part of flagellum)
cap phase?
acrosome forms a distinct cap over anterior portion of nucleus; primitive flagellum from distal centriole begin to elongate; golgi migrates to caudal part of the cell; distal centriole forms axoneme or flagellum and begins to elongate; acrosomic vesicle flattens to form a distinct cap by spreading over the nucleus and allowing it to elongate
acrosomal phase?
acrosome continues to spread until it covers 2/3 of anterior nucleus; nucleus begins to elongate (shifted to one part of the cell); manchette froms (unique system of microtubules) and attaches just posterior to acrosome
maturation phase?
manchette disappears; mitochondria migrate to cluster around flagellum; assembled from nucleus base to anterior 1/3 of tail; form mid-piece; dense outer fibers of flagellum and fibrous sheath are formed; assembly is completed
where is ATP produced?
in the middle piece
Where is mitochondria located?
in the middle piece
function of the neck?
anchors the tail to the head of sperm
spermiation?
once metamorphasis is complete, spermatozoa is release from the sertoli cells to the lumen; most cytoplasm stays and is not release as part of sperm and remains is the sertoli cells to be phagosotized
sertoli cells = ?
nurse cells
cytoplasmic droplet?
remnants of cytoplasm that remains; moves farther down sperm tail as it increases in maturity
where is sperm not motile and not fertile?
epididymal head (proximal CD)
where does sperm have some motility and fertility and can bind to the ova?
epididymal body (translocation CD)
Where is sperm motile, fertile, and can bind to ova?
epididymal tail (distal CD)
Sperm cell types in order?
spermatogonia, primary spermatocyte, secondary spermatocyte, round spermatid, spermatozoa
After spermiation where does the spermatozoa enter?
rete testis to make its way out and continue progression
4 reasons for sertoli cells importance?
support for germ cells, environment for germ cell development and maturation, initiates meiosis, hormonal signals affect the AP (think of sertoli cells as jello)
