PSL300H1 Study Guide - Midterm Guide: Male Reproductive System, Vas Deferens, Seminal Vesicle
PSL300&
Male&Reproductive&System!
!
Male&reproductive&system&à&homeostatic&process&
Ø testes!produce!gametes!(sperm)à!this!is!where!germ!cells!are!stored;!develop!from!the!
bipotential!gonad!à!differentiated!into!a!testis!à!descends!into!the!scrotal!sac!which!forms!
from!the!bipotential!uretral!folds!!
o Internal!structures:!Off!of!the!testis!is!the!vascular!epididymis!and!the!vas!deferens!
which!is!associated!with!glandular!tissue,!seminal!vesicle!and!the!prostate!gland!
o Short!route!à!enters!the!urethra!à!urine!from!the!bladder!exits!through!the!penis!!
Ø grow,!develop,!change!
Ø transfers!by!vas$deferens!
Ø seminal!vesicle!à!adds!seminal!fluid!
Ø prostate!gland!!
o add!seminal!fluid!components!
o duct,!regulates!urine/ejaculate!
Male&puberty!
Ø evolves!on!the!hypothalamus-pituitary-gonadal!axis!
o Have!a!series!of!signals!set!up!!
Ø In!the!hypothalamus,!neurons!pulse!!
o Release!GnRH!à!goes!into!pituitary!à!releases!LH!and!FSH!à!targets!and!changes!
gonad!
Ø LH!stimulates!endocrine!cells!–!steroids!and!other!peptide!hormones!!
o Positive!feedback!loop;!feeding!forward!à!lead!to!frequent!pulsing!of!neurons!to!
release!LH!and!FSH!(more!hormone!production)!à!there!will!be!consequences!since!
these!keep!on!escalating!à!want!to!maintain!certain!levels!of!each!!
§ With!each!round,!these!levels!are!keep!on!getting!higher!and!there!is!a!critical!
threshold!in!which!we!want!to!keep!these!levels!at!
Ø GnRH!à!gonadotropin-releasing!hormone!
Ø LH!à!luteinizing!hormone!
Ø FSH!à!follicle-stimulating!hormone!
o Promote!gamete!production!!
o Gametes!à!germ!cells!(undifferentiated;!incapable!of!fertilizing)!à!develop!spermatids!
(mature!form!of!the!gametes)!à!capable!of!fertilization!
Ø Steroid!hormones!à!androgens,!testosterone!
Ø Hormones!reused!à!female!and!male!(BIPOTENTIAL)!
Gametogenesis!
Ø Gametes!!
o Have!23!chromosomes!
o Germ!cells!start!out!with!46!chromosomes!(we!have!to!throw!away!23!chromosomes!
somehow)!
Ø Process!involves!meiosis!
o DNA!replicated!once!
o Cells!undergo!division!twice!
Ø Mitosis!
o DNA!replicated!once!
o Cells!undergo!division!once!
Ø Testis!à!gametes!produced!in!males!à!in!the!testis,!there!are!tightly!folded!tubes!à!
seminiferous!tubules!à!this!is!where!gametogenesis!takes!place!
o Coming!out!of!these!tubules!are!various!collecting!ducts!which!drain!into!a!structure!
called!the!epididymis!which!is!continuous!with!the!ductus!deferens!which!turns!into!the!
vas!deferens!which!arches!up,!over!the!bladder!and!in!towards!the!seminal!vesicle!and!
the!prostate!
Question!
Ø During!puberty,!hGRH!triggers!release!of!FSH!and!LH,!which!stimulates!steroid!production,!
which!stimulated!hGHR.!This!is!a!feed!forward!loop.!What!will!the!consequence!be!on!the!levels!
of!steroids?!
o Re-stimulate!hormone!production!
o Escalate!increasingly!
o Build!up!levels!of!it!
o Threshold,!changes!occur!
o Gametogenesis!
o Want!critical!threshold!to!be!observed!
Where&are&the&male&gametes?!
Ø Produced!in!the!testes!
o Optimal!at!2-3!degrees!Celsius!lower!than!the!body!temp!
o If!males!are!having!low!sperm!counts,!fertility!issues,!!doctors!tell!them!to!wear!boxer!
shorts!and!baggy!pants!instead!of!tight!briefs!to!keep!the!testicles!away!from!the!body!
à!too!warm,!slows!down!the!production!of!sperm!
Ø Germ!cell!to!mature!spermatid!à!Takes!~64!days!
Ø 200!million!new!spermatids!made!per!day!
o Further!maturation!in!epididymis!à!get!into!the!seminiferous!tubule!à!takes!a!while!
for!it!to!get!through!it!!
Epididymis&
Ø Cross!section!à!see!major!cell!types!!
Ø Previous!lecture!–!talked!about!gonad!development!!
o Talked!about!the!stimulation!of!the!Sertoli!cells!!
Ø Sertoli!cells!(purple)!à!coalesce,!surround!and!encase!columns!of!germ!cells!(blue)!à!germ!cells!
differentiate!as!they!move!down!the!column,!going!through!rounds!of!meiosis!as!they!move!
down!the!column!and!then!they!mature!as!spermatids!with!their!tails!poking!out,!into!the!cavity!
of!the!epididymis!à!released!when!they!are!mature,!and!they!flow!through!the!tubule!and!out!
o (sustentacular!cells)!
o Support!sperm!development!!
Ø Leydig!cells!(sitting!around!on!the!outside)!à!cells!in!between!other!cells!and!other!stuff!!
o (interstitial!cells)!!
o Create!and!secrete!testosterone!
Testes&have&a&blood&barrier!
Ø Blood!barrier!(In!the!brain,!scent,!testes)à!many!different!factors!in!blood!à!some!tissues!à!
some!factors!are!very!toxic;!detrimental!to!some!of!the!biology!and!physiology!that!is!trying!to!
occur!if!some!materials!get!in!there!
Ø stem!cells!are!very!sensitive!à!undifferentiated!à!keep!undifferentiated!state!à!maintained!
by!the!removal!of!signals!to!differentiate!rather!than!the!creation!of!signals!telling!it!to!not!
differentiate!(essentially,!you!are!taking!away!the!signals!that!promote!differentiation)!
Ø Blood-testis!barrier!!
o Basal!lamina!layer!on!the!outside!of!the!epididymis!coil!à!find!the!germ!cells!in!the!
basal!lamina!layer!!
§ Outside!of!that!are!the!leydig!cells!and!the!capillary!cells!(none!inside!
epididymis)!!
o This!is!your!BARRIER:!endothelial!cells,!the!basal!lamina!structure!!
o Tight!junctions!à!membrane!between!sertoli!cells!à!like!a!zipper!–!stop!things!from!
moving!between!compartmentsà!completely!encased!these!germ!cells!(these!are!not!
touching!the!cells!that!are!differentiating)!à!there!is!a!little!finger!projection!from!the!
cytoplasm!that!is!keeping!them!trapped!in!there!
§ Creates!a!compartment!–!a!niche!for!germ!cells!and!spermatogonium!
Ø Prevents!exposure!to!some!hormones!and!other!molecules!
Hormonal&control&of&spermatogenesis&
Ø Continuously!going!to!happen!à!don’t!want!to!run!out!of!germ!cells!à!70-80!years!old!à!can!
still!give!rise!to!fertilization!(there!isn’t!a!well-defined!upper!limit!of!fertility!in!males)!
Ø Uses!the!same!hypothalamus-pituitary-gonadal!axis!for!signalling!!
Ø Feedback!loop!
Ø FSH!and!LH!are!both!involved!
Ø Testosterone!
o Negative!regulator!of!GnRH!and!LH!
Ø Inhibin!à!peptide!hormone!
o Negative!regulator!of!FSH!
Ø GnRH!signals!to!the!pituitary!to!release!FSH!and!LH!!
FSH&Sertoli&cell&signalling&!
Ø FSH!strikes!the!Sertoli!cells!
o Support!sperm!development!!
o Secrete!inhibin,!produces!androgen-binding!protein!(ABP!–!binds!testosterone)!
Document Summary
Testes produce gametes (sperm) this is where germ cells are stored; develop from the bipotential gonad differentiated into a testis descends into the scrotal sac which forms from the bipotential uretral folds. Prostate gland: add seminal fluid components, duct, regulates urine/ejaculate. Evolves on the hypothalamus-pituitary-gonadal axis: have a series of signals set up. In the hypothalamus, neurons pulse: release gnrh goes into pituitary releases lh and fsh targets and changes gonad. With each round, these levels are keep on getting higher and there is a critical threshold in which we want to keep these levels at. Fsh follicle-stimulating hormone: promote gamete production, gametes germ cells (undifferentiated; incapable of fertilizing) develop spermatids (mature form of the gametes) capable of fertilization. Hormones reused female and male (bipotential) Gametes: have 23 chromosomes, germ cells start out with 46 chromosomes (we have to throw away 23 chromosomes somehow) Process involves meiosis: dna replicated once, cells undergo division twice.
