Required Reading Flashcards
List the 4 steps that most occur before the embryo can attach to the uterus.
- development w/in the confines of the zona pellucida
- hatching of the blastocyst from the zona pellucida
- materinal recognition of pregnancy
- formation of the extraembryonic membranes
A ______ is an organism in the early stages of developement.
embryo
What is the term for a potential offspring that is still w/in the uterus, but is generally recognizable as a member of a given species?
Fetus
What is the term for the product of conception?
Conceptus
“Conceptus” includes what 3 things?
- embryo during the early embryonic stage
- embryo & extraembryonic membranes during the preimplantation stage
- fetus & placenta during the post-attachement phase
When does syngamy occur?
when the female & male pronuclei fuse
into a single diploid nucleus
What is the term for the cells in a 2-celled embryo?
Blastomeres
AKA
Daughter cells
What is the 8-celled embryonic stage called?
Morula
What 3 components make up a Blastocyst?
- ICM (inner cell mass)
- Blastocoele
- Trophoblast
What is the term used to describe the ability of a single cell to give rise to a complete, fully formed individual?
What embryonic stages exhibit this trait?
- Totipotent
- Blastomeres from the 2-, 4-, 8- & 16- cell embryos
When does the morula reach the cow’s uterus?
4-7 days post ovulation
When does the blastocyst reach the cow’s uterus?
7-12 days post ovulation
When does the hatching reach the cow’s uterus?
9-11 d post ovulation
Where does fertilization occur?
in the Ampulla of the Oviduct
What 3 forces govern the hatching of the blastocyst?
- growth & fluid accumulation w/in the blastocyst
- production of enzymes by the trophoblastic cells
- contraction of the blastocyst
Which structure gives rise to the chorion?
trophoblastic cells
When is the blastocyst totally dependent upon the uterine environment for survival?
after the zona pellucida ruptures
List the 4 extraembryonic membranes
that make up the preattachment embryo.
- yolk sac
- chorion
- amnion
- allantois
Which 3 embrynoic structures give rise to the
Amnion & Chorion?
- Trophoblast
- primitive endoderm
- primitive mesoderm
Which structure gives rise to the yolk sac?
primitive endoderm
Which embryonic structure makes up the Allantois?
the primitive gut
What is the fetal contribution to the placenta?
the allantochorion
What must occur to prevent luteolysis
& termination of pregnancy?
maternal recognition of pregnancy
What does the blastocyst secrete to block the synthesis of uterine oxytocin receptors of the cow?
Interferons
(bIFN-t/bTP-1)
What is the critical time period for maternal recognition of pregnancy by the cow?
13-14 days post ovulation
What is the critical time of embryo attachement in the cow?
18-22 days post ovulation
What is required for a successful pregnancy?
high blood [Progesterone]
List some advantages of embryo transfer.
- circumvention of seasonal reproduction
- enhanced generation of offspring in monotocous species
- enhanced repro potential of endangered species
- enhanced genetic diversity across a wide geographical region
List some things involved in
successful embryo transfer.
- synchronizing the cycles of donors & recipients
- superovulation of the donor animal
- AI of the donor female
- recovery of embyros from the donor
- maintenance of vialble embryos in vitro
- transfer of embryos to recipient females
What must occur in order for embryos from the donor animal to develop w/in the recipient animal?
the stage of their cycles must coincide
What is usually used to achieve superovulation?
FSH
(gonadotrophins)
How can you recover oocytes from the
ovaries of a donor cow?
- surgically
- using an U/S to aspirate follices
- post-mortem in an abattoir
List the 5 major steps of Embryo transfer in the cow.
- sychronization of recipients w/ donor
- Superovulation of donor
- A.I of donor w/ semen from a superior bull
- Recovery & I.D. of viable embryo
- Transfer of viable embryo into synchronized recipients
