Fertilization Flashcards
Oocytes are arrested in ________ and remain dormant until ______________
Oocytes are arrested in prophase I and remain dormant until after puberty
What are the phases of oocyte development?
Meiosis I: begins during fetal development
Prophase I: arrested until puberty
Meiosis I: resumes when follicle recruited in adult life
Meiosis II: begins when follicle is recruited
Metaphase II: arrested
Metaphase II at ovultation
Meiosis resumes only if the oocyte is fertilized by a sperm
What are the 3 events of sperm capacitation?
Changes in surface glycoproteins
Alteration of the lipid structure of the plasma membrane
Hyperactivated motility
What layer of the oocyte must the sperm penetrate? Where does the sperm bind?
Cumulus cells surround oocyte
Binds to zona pellucida
What triggers and acrosome reaction? What is that reaction?
Influx of calcium
Outer acrosomal membrane fuses with the sperm plasma membrane, acrosomal enzymes are released and digest a pathway through the zona
What is the cortical reaction?
Alters the zona pellucida and prevents penetration by additional sperm (‘zona hardening’)
Why an egg can only be fertilized by one sperm
Where does fertilization occur?
Near the ampulla-isthmus junction
How is equine embryo physiology unique?
Only viable embryos are transported distally through the isthmus and pass through the UTJ into the uterus
Equine embryos must produce prostaglandin E2 which relaxes the inner circular smooth muscle of the oviduct and allows embryo passage
What hormone is required by all females to maintain pregnancy?
Progesterone
Initial source = corpus luteum (or placenta)
Maternal Recognition of Pregnancy: Bovine, Ovine
Secretion of interferon tau, which inhibits the production of oxytocin receptors in the endometrium so that oxytocin cannot stimulate prostaglandin F2a synthesis
Maternal Recognition of Pregnancy: Pigs
Production of estradiol re-routes PGF secretion into the uterine lumen
Minimum of 4 embryos
How to bovine and ovine embryos change with Maternal Recognition of Pregnancy?
Embryos elongate to fill the uterine horn ipsilateral (same side) to corpus luteum
How do pig embryos change with Maternal Recognition of Pregnancy?
Embryos migrate through the uterus
How do equine embryos change with Maternal Recognition of Pregnancy?
Embryos remain spherical and migrate throughout the entire uterine lumen (both horns and uterine body) multiple times each day
Why there is a capsule
Define: Dizygotic Twins
Non-identical twins
Arise from fertilization of two oocytes
Two ovulations
