The Three Trimesters of Gestation and the Three Stages of Labor

Development and Inheritance
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1.What activity during oocyte activation prevents penetration by additional sperm?
The cortical reaction releases the zonal inhibiting proteins (ZIPs)enzymes, which inactivates the sperm receptors while hardening the zona pellucida. This prevents fertilization by additional sperm and is also known as the block to polyspermy (Martini, Nath & Bartholomew, 2018).
2.Outline the events between exposure of the oocyte to spermatozoa and the formation of the first blastomere pair.
Fertilization occurs when a sperm fuses with an egg (oocyte), and a single nucleus is formed when the fertilized egg or zygote is formed. A zygote consists of all hereditary information where genetic material is from the male and another half from the woman. Blastomeres are the smaller cells that form after the division of the zygote (Marieb& Smith. 2016).
There is fertilization and oocyte activation when there is fertilizing sperm. Then the pronuclei develop, and DNA synthesis occurs where the sperm is absorbed into the cytoplasm, and the female pronucleus develops. This is followed by the beginning of the spindle formation. After this, the amphimixis occurs, and cleavage begins where the maternal and paternal chromosomes align on the metaphase plate. There is then the first cleavage forming the blastomere pair, whereby the first cleavage division nears completion after fertilization.
3.List and briefly characterize the three trimesters of gestation.Gestation consists of the first, second, and third trimesters:
* The first trimester is the pre-embryonic, embryonic, and early fetal development period, where all the major organ systems start to appear (Martini, Nath & Bartholomew, 2018).
* The second trimester is characterized by the development of fetal organs and organ systems. This process takes approximately six months, where the body takes shape and becomes more proportional, while the fetus becomes more human-like human (Martini, Nath & Bartholomew, 2018).
* There is rapid fetal growth in the third trimester,and the fetus's major organ systems become fullyfunctional (Martini, Nath & Bartholomew, 2018).
4.Desc...