Male Repro Flashcards
What is the developmental origin of sertoli cells
coelomic epithelial cells of the gonadal ridge
What is the germ cells originate from?
they migrated from the yolk sac
What is the developmental origin of leydig cells?
mesenchyme of gonadal ridge
What cells synthesize testosterone
leydig cells
What is the precursor hormone to testosterone
progesterone
What do sertoli cells secrete
AMH
Inhibin
Estrogen
Androgen binding protein
What are the three repro important areas f the hypothalymus?
Paraventricular nucleus
the surge center
the tonic center
Which center of the hypothalamus is most important in males
tonic center
What is the function of the tonic center in males
small frequent surges of GnRH from the hypothalamus induces the production of LH which stimulates the production of testosterone
Which center of the hypothalamus is most important in females
the surge center
What is the function of the surge center
a high amplitude surge of GnRH is necessary to produce a large surge of LH which is needed for ovulation to occur
From where is FSH and LH secreted?
anterior pituitary
What does testosterone negatively feedback on?
LH and GnRH
What does inhibin (from sertoli cells) negatively feedback on?
FSH
The hypothalamus is inherently ______
female
What defeminizes the hypothalamus during fetal development
estradiol (testosterone converted to estradiol via aromatase)
How does testosterone defeminize the hypothalamus during development
-Testosterone is produced by fetal testes
-testosterone is converted in the brain to estradiol by aromatase
-estrodiol in the brain eliminates the surge center
What enzyme converts testosterone to estrodiol in the brain
aromatase
If estradiol defeminizes the hypothalamus, how do females not defeminize their own brain?
alpha-fetoprotein binds to estradiol (gonadal) preventing it from crossing the blood brain barrier in the CNS
What protein binds gonadal estradiol in the fetus
alpha-fetoprotein
Where is alpha-fetoprotein made in the fetus
made by yolk sac and fetal liver
What is the function of alpha-fetoprotein?
a protein produced by the fetal liver to bind to gonadal estrogen to prevent it from crossing the blood brain barrier
What is the function of androgen binding protein
binds to testosterone and increases concentration of testosterone within seminiferous tubules
Where is androgen binding protein produced
sertoli cells
What are the three major factors leading to puberty
Metabolic
Environmental/social cues
Genetics/breeding
How do GnRH neurons inhibit puberty
they have increased sensitivity to negative feedback of testosterone
There is ______ sensitivity of GnRH neurons to ______ as puberty approaches
decreased, testosterone
once there is a decreased sensitivity of GnRH neurons as puberty approaches what happens?
testosterone can now influence the hypothalamus to increase secretion of LH
How does LH influence testosterone production
it increases it
What triggers change in hypothalamic testosterone sensitivity at puberty?
-neurons can sense changes in blood glucose and FAs
-Leptin receptors
True/false: There is a certain level of fatness required for puberty?
true
What converts testosterone to DHT in cells?
5alpha reductase
true/false: Testosteron/DHT is necessary for growth and maturation of accessory sex glands
true
What are two ways to have the accessory sex glands regress
castration or anything that interferes with GnRH/LH
What are spermatogonia and how do they divide
stem cells
divide by mitosis
What are spermatocytes and how do they divide
Priamary- meiosis I
Secondary- Meiosis II
How long does a cycle of spermogenesis take
60 days
True/False: sperm production is always “on”
false, seasonal breeders can turn it off or on
What is needed within the seminiferous tubules to have spermatogenesis
extremely high levels of testosterone
What cells have LH receptors and produce testosterone
leydig cells
True/False: Testosterone production is intimately associated with LH production
true
GnRH results in the production of what hormones?
LH and FSH
What would happen if LH was secreted for hours instead of minutes
secretion of testosterone for hours
metabolic overload for test clearance
sustained negative feedback on GnRH
reduced LH secretion
reduced test production
What is the function of FSH in males
stimulates sertoli cells
What is the function of LH in males
stimulates leydig cells
What is the rate limiting step in testosterone synthesis
steroidogenic acute regulatory protein
True/False: testes are an immune privileged site
true
What are the three components of immune privilege?
anatomincal (complex junctions)
Physiological (specialized transport systems)
Immunological ( blood testes barrier. immune cells within interstitial space)
Where are spermatagonia in the seminiferous tubule
basal compartment
Where are mature sperm in the seminiferous tubule
adluminal compartment
Where is sperm stored in the testes
in the tail of the epididymis
True/false: sperm can trickle and escape out of the tail into the ductus deferens to pelvic urethra and end up in urine
true
What moves sperm through the ductus deferens
smooth muscle producing rhythmic contractions
Where is sperm concentrated in the testes
in the head of the epididymis
True/False: aquaporins are utilized in the concentration of seminal fluid
true
sperm must be ______ to be motile, but also must be ________ from being motile
prepared, repressed
______ is necessary for sperm motility
cAMP
Low calcium levels in the sperm tail could ______ motility
prevent
Where does capacitation occur?
in the isthmus of the oviduct
Where does changes to sermatic plasma membrane that will enable capacitation to occur
in the epididymis
What does change in the sperm cytoplasmic droplet indiciate
maturity, a more proximal droplet can indicate immature sperm
True/False: Sperm from the entirety of the epididymis is ejaculated
false, only sperm from the tail
True/false: infrequent and very frequent ejaculations can affect sperm quality
true
what are 4/5 requirements for erection
-Elevated arterial inflow
-dilation of blood sinuses
-restricted venous outflow
-elevated intrapenile pressure
+/- relaxation of retractor penis muscle in certain species
What is the main neural input on a non erect penis
sympathetic
what is the main neural input on an erect penis
parasympathetics
Parasympathetics release what neurotransmitter during penile erection
NO to allow vasodilation and blood sinus relaxation to allow for engorgment
What are the 4 steps of erection to emission
- sensory stimulus
- Hypthalamic input
- oxytocin release by posterior pituitary
- movement of sperm
What is the role of oxytocin in erection to emission
it contracts smooth muscle which then move sperm into the ductus deferens and pelvic urethra, positioning sperm for ejaculation
what secretions from the accessory sex glands contribute to the seminal plasma
-fructose
-ovulation induction factor
-substance for female tolerance
-+/- copulation plug
-fluid for volume (specifically pigs)
Define ejaculation
reflex expulsion of spermatazoa and seminal plasma from the male repro tract
ejaculation is controlled by what neural inputs
sympathetics
sensory stimuli of the glans is transmitted by what nerve to the spinal cord
pudendal nerve
what are the three main muscles targeted for ejaculation
urethralis, ischiocavernosus, bulbospongiosis
Where does phagocytosis of sperm occur
vaginia, ,cervix, uterus
true/false: females can sometimes produce antisperm antibodies
true
Where does fertilization take place
ampulla of oviduct
where does sperm sequestration take place
isthmus of oviduct
what is capacitation
changes in the membrane of the sperm so that the acrosome reaction can take place
What is the main result of capacitation
changes in sperm motility pattern from straight, linear to spiral trajectory
What is the acrosome reaction
the reaction allows sperm to penetrate the zona pellucida, it modifies the sperm membrane such that it can fuse with the oocyte membrane
where does the acrosome reaction membrane modification occur on the sperm
equatorial segment
True/false: acrosomal damage is reversible
false
what are 4 situations that can induce premature acrosome reaction or acrosomal damage
-changes in osmotic pressure
-sudden cooling/heating
-marked change in pH
What is the enzyme that hydrolyzes zona proteins to aid in sperm interaction with the oocyte
acrosin, which is released from acrosome reaction
What flagellar activity is most effective in drilling through the zona
hyper activated motility (spiral)
Briefly describe the fusion of the sperm with oocyte
-sperm has penetrated the zona
-sperm settles on oocyte membrane
-plasma membrane of oocyte fuses with fusion proteins on equatorial segment of sperm
-sperm is engulfed
-sperm nuclear membrane dissolves
once sperm has fused with oocyte, what happens to the oocyte
fusion induces cortical reaction ( exocytosis of cortical granules). these granules harden the zona so that no other sperm can penetrate