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Early Embryogenesis and Maternal Recognition of Pregnancy - Coggle Diagram
Early Embryogenesis and Maternal Recognition of Pregnancy
Embryo develop into blastocyst
The presence of male and female pronuclei withing the cytoplasm of the oocyte characterizes a developmental stage of the newly fertilized oocyte
The cell formed is called an ootid
One of the largest cells in the body
Has an enormous cytoplasmic volume relative to nuclear volume
Forms a zygote
Undergoes a series of mitotic divisions called cleavage divisions
Blastomeres undergoes subsequent divisions, yielding 4,8 and 16 daughter cells
Hatch from the zona pellucida
As blastocyst continues to undergo mitosis, pressure within the embryo increases
These enzymes weaken the zone pellucida so that it ruptures easily as growth of the blastocyst continue s
Pressure pulses coupled with continual growth and enzymatic degradation cause the zona pellucida to rupture
Small crack or fissure in the zona pellucida develops
Cells of blastocyst squeeze out of the opening
Blastocyst becomes a free-floating embryo within the lumen of the uterus
After hatching, the conceptus undergoes massive growth
Soon, the blastocyst will occupy the space in both uterine horns
Due to the development of a set of membrane called the extraembryonic membranes
Consists of yolk sac, chorion, amnion, and allantois
Develop a functional trophoblast
The primitive endoderm forms beneath the inner cell mass and begins to grow downward
Evagination forms a yolk sac
Made within the extraembryonic membranes of the preattachment embryo
Once newly formed primitive endoderm fuses with the trophoblast to form a double membrane with is called the chorion
Chorion sends wing-like projections above the embryo, and amnion begins to form
Amnion is filled with fluid and serves to protect the embryo from mechanical perturbations and serves as an anti-adhesion material to prevent tissues in the rapidly developing embryo from adhering to each other
Produce materials that prevent luteolysis or that enhance luteal function
Must happen for early embryogenesis and to continue unto an established pregnancy
Conceptus must provide a timely biochemical signal or a pregnancy will terminate
Maternal recognition of pregnancy must occur prior to luteolysis
In the ewe and the cow, the free-floating blastocyst produces specific proteins that provide the signal to prevent luteolysis
Produces two specific proteins
Ovine trophoblastic protein 1
Both of these proteins belong to a class of materials known as interferons
Most interferons are nonspecific glycoproteins produced by leukocytes, fibroblasts, lymphocytes and trophoblastic cells
Interferons have antiviral action and alter the function of target cells
Bovine trophoblastic protein 1