02.08.24 animalreproduction aaaaaaa.pdf

a

1. TRANSPORTATION AND
SURVIVABILITY OF GAMETES IN
FEMALE REPRODUCTIVE TRACT
Dr Bhavna
Assistant Professor cum Junior Scientist
Deptt. of Veterinary Gynaecology and Obstetrics
Bihar Veterinary College, BASU, Patna

2. Site of semen deposition
Siteofdepositionofsemenvaryfromspeciesto
species.
Incattleandsheep,thesmallvolumeofsemenis
ejaculatedintocranialendofvaginaandinto
cervix.
Inhorseandswine,thevoluminousejaculateis
depositedthroughtherelaxedcervicalcanalinto
uterus.

4. Threestagesarerecognizedinspermtransportin
thefemalereproductivetract:
1.Rapidtransport
2.Colonizationofspermreservoir
3.Slowreleaseandtransport

5. Rapid Transport
ImmediatelyafterAIormating,spermatozoapenetratethe
cervicalmucuslayerwheresomearequicklytransported
throughcervicalcanal.
Thisphasetakes2-10minutesandmaybefacilitatedby
spermmotilityaswellasincreasedcontractileactivityof
myometriumandmesosalphinxduringcourtshipandcoitus,
someofspermatozoareachinternalosofcervixwithin1.5-3
minutesafterAI.
Fertilizationoccursonlywhenacriticalno.ofspermatozoa
reachthesiteoffertilization.

6. Colonisationof sperm reservoir
Massiveno.ofspermatozoaaretrappedinmucosalfold
ofcervicalcrypts,formingreservoirs.
Themorespermatozoaentercervicalreservoirthemore
reachtheoviduct,thusincreasingthechanceof
fertilization.
Inspecieswhereejaculationoccursinuterus,sperm
reservoirarelocalizedinuterotubal(pig)orin
endometrialglands(dogs).

7. Slow Release and Transport
Afteradequatespermreservesareestablishedin
reproductivetract,thespermatozoaarereleasedfor
prolongedperiod.
Variousanatomical&physiologicalbarriersprevent
massiveno.ofspermsfromreachingsiteof
fertilization.

8. Sperm transport in the uterus
Myometrialcontractionsplayamajorroleinthe
transportofspermatozoainto&throughuterus.
Presenceofspermsintheuterusinducesendometrial
leucocyticresponsewhichenhancesphagocytosisof
excesssperms.

9. Transport in oviduct
Oviducthasuniquefunctionofconveyingspermatazoa&ovum
inoppositedirectionalmostsimultaneously.
Pattern&rateofspermtransportthroughtheoviductare
controlledbyseveralmechanisms,suchasperistalsis&
antiperistalsisofoviductalmusculature,complexcontractionsof
oviductalmucosalfolds&themesosalphinxfluidcurrentsand
countercurrentscreatedbycilliaryaction.
Frequency&amplitudeofcontractionsofoviductal
musculaturearecontrolledbyovarianhormones&components
ofseminalplasmalikePGF
2α.

10. Endocrine control of sperm transport
Thepenetrabilityofspermatozoaisgreatlyinhibitedby
progestationalcervicalmucus(lutealphase){thathelps
femaletoprotectagainstnecessaryexposuretoforeign
proteinsofsemen}.
Oxytocin,sympathetic&parasympatheticnervoussystemalso
controlspermtransport.
Epinephrine,Acetylcholine&histaminecanalteruterine
contactionsbuttheireffectistransitory.

11. Amultistepphenomenon,initiatedby
interactionandsubsequentfusionof
maleandfemalegamete,resultingin
formationofsinglecellofanew
individual.
Fertilization

12. The process
Spermatozoonfirstencounterandpenetratecumulusoophorus.
Acrosomalactivationoccurs,inneracrosomalmembrane
contractsthezonapellucida,whereenzymesexposedon
membranesurfaceallowpenetrationintoperivitellinespace.
Equatorialregionofspermattachesandfuseswiththevitelline
membranestimulatingthecompletionofsecondmeiotic
division.
Alargemalepronucleusandsmallerfemalepronucleusform
followingextrusionofthesecondpolarbody.
Pronucleiimigratetotheoocytecenterwherethenuclear
envelopsdisperseandprophaseofthefirstmitosisdivision
begins.

16. Three critical events
Spermmigrationbetweencumuluscells.
Spermattachmentandmigrationthroughzona
pellucida.
Fusionofspermandovumplasmamembranes.

17. Thereisevidencethatasubstanceproducedbycumulus
oophorusofrabbitovamaystimulatespermmotility.
Thisfactormayplayasecondaryroleinthesperm–
ovumencounter,sinceperistalticcontractionsofthe
ampullaincreasethechancesofovum-spermcontact.
Similarly,hyaluronidasepresentinbullacrosomeand
arylsulphatefromboaracrosomecausescellsof
cumulusoophorustodisperse.

18. Spermatozoanfirstencountersandpenetratescumulus
oophorusuponitscellulardisintegration.
Firstpolarbodyispresentintheperivitellinespace
withametaphasespindleofsecondaryoocytepresent
inthecytoplasm.
Theinneracrosomalmembranecontactsthezona
pellucidawhereenzymesexposedonthemembrane
surfaceallowpenetrationintotheperivitellinespace.

19. Equatorialregionofspermheadattachesandfuses
withthevitellinemembranestimulatingcompletion
ofsecondmeioticdivision.
Thelargemalepronucleusandsmallfemale
pronucleusareformedfollowingextrusionofthe
secondpolarbody.

20. Immediatelyafterfertilizationtheovumsurface
changestopreventfusionofadditional
spermatozoa.
Whenthismechanismfails,polyspermicfertilization
canresult,withformationofpolyploidembryos
thatundergoesembryonicdeathorabnormal
development.

24. Causes of fertilization failure
1.Ovulation abnormalities
2.Sperm and its transport abnormalities
3.Endocrine imbalance
4.Early embryonic death