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CH 13 Early embryogenesis and maternal recognition of pregnancy - Coggle…
CH 13 Early embryogenesis and maternal recognition of pregnancy
4 steps must be achieves before embryo can attach to uterus
Development within the confines of the zona pellucida
Hatching of the blastocyst from the zona pellucida
Maternal recognition of pregnancy
Formation of the extraembryonic membranes
Hatching of the blastocyst is governed by 3 forces
Growth and fluid accumulation within the blastocyst
Production of enzymes by the trophoblastic cells
contraction of the clastocyst
The extraembryonic membranes of the preattachment embryo consists of:
Yolk sac
chorion
Primitive endoderm and mesoderm give rise to this
amnion
amniotic fluid Serves as a anti- adhesion material to prevent tissues in the rapid developing embryo from adhering to each other
Allantois
Fluid filled sac that collects waste from the embryo
In most species, conceptus must provide a timed biochemical signal or the pregnancy will fail
P4 must be at high levels so that embryogenesis and attachment of the developing conceptus to the endometrium can take place
Maternal recognition of pregnancy must occur prior to luteolysis
Equine conceptus must make extensive contact with the endometrial surface to initiate and complete maternal recognition of preganacy
Women maternal recognition of pregnancy is provided by a hormone called human chorionic gonadotropin hCG
Maternal recognition of pregnancy in the dog and cat probably does not require a signal from the conceptus
Embryonic transfer
Advantages
Circumvention of seasonal reproduction
Enhanced generation of offspring in monotocous species
Assisted reproduction for infertility in humans
Enhanced reproductive potential of endangered species
Enhanced genetic diversity across a wide geographical region (ship embryos rather than animals)
Successful transfer involves:
Synchronizing the cycles of donors and recipients
Superovulation (hyperstimulation of the ovaries) of the donor
Artificial insemination of the donor female
recovery of embryos from the donor
maintenance of viable embryos in vitro
transfer of embryos to recipient females
Recovery of oocytes from ovaries is accomplished by:
Surgically exposing the ovary and aspirating follicles
Non- surgically aspirating follicles utilizing ultrasonography
aspirating follicles postmortem in an abattoir