Fertilization Flashcards
Where do sperm acquire maturity ?
Passage through epididymis
Where does sperm gain maximal fertility?
Female tract (usually uterus)
What are the steps of ejaculation?
Intromission
Sensory stimulation from glans penis (temp and pressure)
Afferent to spinal cord —> motor neuron (pudendal nerve)
Contraction of urethralis, bulbospongiosus and ischiocavernosus muscles
Expulsion of semen
Where is semen deposited during natural mating in the cow, ewe, doe, and bitch?
Anterior vagina
Where is semen deposited during natural mating in the mare?
Uterus
Where is semen deposited during natural mating in the sow?
Cervix
How are sperm lost once in the female tract?
Retrograde loss
Phagocytosis by neutrophils
Where is capacitation completed?
Oviduct - sperm become hypermotile
What must occur for a sperm to fertilize an oocyte?
Hyperactive motility Binding to ZP Acrosome reaction Spermatozoa penetrates oocyte Sperm-oocyte fusion Decondensation of sperm nucleus Male and female pronuclei form
Sperm are continually delivered to the oviducts from what reservoir sites?
Cervix
UTJ
This extends the time in which fertilization can occur
Where are sperm stored in the oviduct?
Isthmus
What is the purpose of seminal plasma?
Mixing of sperm and seminal plasma coats the sperm with proteins that must be removed for max fertility
What is capacitation?
Stripping of membrane proteins (from seminal plasma) by uterine factors
- over tail improves motility
- mover the mid-piece improves metabolism
- over the head allows binding to ZP
Resulting in hyper activated sperm in ampulla
What initiates the acrosome reaction?
Binding to ZP
Plasma membrane over the acrosomal membranes fuses use acrosomal membrane —> vacuolation
Acrosomal enzymes can pass broth
Vesicles are sloughed off leaving inner acrosomal membrane and nuclear cap intact
Enters perivitelline space
Membranes fuse
Cortical reaction induced
What is the cortical reaction?
Sperm head attaches to oocyte plasma membrane (vitelline membrane) and initiates block to polyspermy
ZP hardens
Vitelline membrane changes
Where does fertilization take place at in the cow?
Ampullaisthmic junction
What is syngamy?
Fusion of male and female pronuclei (forms zygote)
What barriers prevent polyspermy?
Cumulus cells
Zona pellucida — oocyte cortical granules are released into the perivitelline space (cortical reaction)
Oocyte membrane
What stages does a fertilized embryo go through prior to attachment?
Zygote
Two celled stage
Four celled stage
Eight celled stage
Morula
Early blastocyst
Hatching blastocysts
Hatched blastocyst
Each blastomere is totipotent up the the ________ cell stage
8-16
What is totipotent?
The ability of a single blastomere to develop into a fully formed individual animal
How long does it take the zygote to travel from the uterine tubules to the uterus?
4 days
What is freemartinism?
Male and female twins..
Anti mullerian hormone from male blocks formation of the Müllerian duct in the female
—> clitoral enlargment and brain changes like a male (male adult behavior)
What is the shape of the ruminant hatched blastocyst? How is the mare different?
Ruminant= Filamentous thread-like
Mare = remains spherical
