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Ch. 13 - Early Embryogenesis and Maternal Recognition - Coggle Diagram
Ch. 13 - Early Embryogenesis and Maternal Recognition
A successful pregnancy requires that the preattachment embryo:
Hatches from the zona pellucida
Develops a functional trophoblast
Develops into a blastocyst
The early embryo must secrete materials that prevent luteolysis or that enhance luteal function to maintain pregnancy
Conceptus:
the product of conception, which includes:
The embryo and extra-embryonic membranes during the preimplantation stage
The fetus and placenta during the post-attachment phase
The embryo during the early embryonic stage
Four steps must be achieved before the embryo can attach to the uterus:
Hatching of the blastocyst from the zona pellucida
Maternal recognition of pregnancy
Development within the confines of the zona pellucida
Formation of the extra-embryonic membranes
Hatching of the blastocyst is governed by three forces:
Production of enzymes by the trophoblastic cells
Contraction of the blastocyst
Growth and fluid accumulation within the blastocyst
The extraembryonic membranes of the preattachment embyo consist of the:
Chorion
Amnion
Yolk sac
Allantois
In the cow and the ewe the free-floating blastocyst produces specific proteins that provide the signal for prevention of luteolysis
Ovine trophoblastic protein 1 (oTP-1)
Bovine trophoblastic protein 1 (bTP-1)
Pregnancy Recognition
Mare - 3 proteins/estrogens
Queen - none needed
EWE - oIFN-T
Sow - estradiol (E2)
Cow - bIFN-T
Woman - hCG
Bitch - none needed
Embryo Transfer
The advantages of embryo transfer are:
Enhanced reproductive potential of endangered species
Enhanced generation of offspring in monotocous species
Enhanced genetic diversity across a wide geographical region (ship embryos rather than animals)
Circumvention of seasonal reproduction
Assisted reproduction for infertility in humans
Successful embryo transfer involves:
Artificial insemination of the donor female
Recovery of embryos from the donor
Superovulation (hyperstimulation of the ovaries) of the donor
Maintenance of viable embryos in vitro
Synchronizing the cycles of donors and recipients
Transfer of embryos to recipient females
Recovery of oocytes from ovaries can be accomplished by:
Non-surgically aspirating follicles utilizing ultrasonography
Aspirating follicles postmortem in an abattoir
Surgically exposing the ovary and aspirating follicles