Fertilization is the process of two different cells recognizing one another. The process of fertilization is comprised of four distinct phases. The first phase of conception involves the preparation of the sperm. The sperms that are ejaculated cannot fertilize immediately because they are not fertile; instead, they undergo a process known as capacitation. During the capacitation process, calcium levels rise, sperm motility is triggered, and the frequency of the sperm’s tail changes (Zhang et al., 2018). Consequently, this creates a way for the fertilization process to start taking place.
The second step of conception involves the attachment of sperm and egg. The thick zona pellucida inhibits sperm from adhering to the egg’s plasma membrane throughout the process. The unfertilized egg includes zona pellucida glycoproteins (ZPGPs), which function as a receptor for the modified sperm (Zhang et al., 2018). Sperms that do not come into contact with the egg and its zona pellucida bid the ZPGP II via galactosyl transferases. The UDP-gal binds to its location on the galactosyl transferase during this step. Multiple points of fusion between the outer plasma membrane of the acrosome and the plasma membrane result in the release of serine protease and N-acetylglucosaminidase from the acrosome (Zhang et al., 2018). Thus, allowing the sperm to be absorbed into the egg through the fusion and elongation of the microvilli of the egg.
The final phase of the conception process is the egg’s reaction. During fertilization, the egg avoids polyspermy, which causes developmental abnormalities. After sperm and egg fusion, the egg releases a cortical reaction that prevents polyspermy from occurring. Ovoperoxidase functions as a catalyst for cross-linking of tyrosine residues in the extracellular matrix, and hydrolase destroys o-linked oligosaccharides on ZIGP III during the polyspermy process (Zhang et al., 2018). Thus, the fertilization process involves chemical and biological reactions that involve enzymes.
A pregnant woman experiences three stages of pregnancy after fertilization. The initial phase lasts thirteen weeks and begins soon after fertilization (Zhang et al., 2018). At 12 weeks, the fertilized egg transforms into a fetus measuring approximately 6 cm in length. The intestines, brain, and stomach begin to form, and the heart begins to beat. As the baby’s legs and arms begin to develop, the mother begins to experience “buds,” or minor bumps. The woman experiences breast discomfort, frequent urination, fatigue, and nausea (Zhang et al., 2018). Thus, hormonal changes render the mother exhausted, irritable, or irritable.
The second phase of pregnancy spans weeks 14 to 26 (Zhang et al., 2018).In week 14, the baby grows to approximately 7.5 centimeters and 30 grams. At week 26, the baby would have measured approximately 23 centimeters and weighed 820 grams. During these three months, the baby’s organs will continue to develop, and the kidney, liver, and pancreas will begin functioning. The woman experiences less nausea, restful sleep, abdominal pain, constipation, and heartburn. As her blood volume increases to meet the demands of all the growths occurring within her, the woman will gain weight. As the fetus can move freely within the amniotic sac of the uterus by week 19 (Zhang et al., 2018). Thus, allowing the women to experience fetal movement.
By week 36 of gestation, the baby is approximately 47 cm long and weighs approximately 2.6 kg. The baby’s head rests lower on the woman’s pelvic bone in preparation for labor. By week 40, the baby will be approximately 50 centimeters long and weigh approximately 3.4 kilograms; at this point, the baby is ready to be born. A woman suffers from shortness of breath, urinary incontinence, and difficulty sleeping. In the final weeks of pregnancy, the cervix softens, and the woman produces a mucus plug that sits within the cervical canal during pregnancy (Zhang et al., 2018). Thus, paving the way for easier and faster delivery that allows the woman to experience little pain during giving birth.
Reference
Zhang, L., Xu, W.-H., Fu, X.-H., Huang, Q.-X., Guo, X.-Y., Zhang, L., Li, S.-S., Zhu, J. and Shu, J. (2018). Therapeutic role of granulocyte colony-stimulating factor (G-CSF) for infertile women under in vitro fertilization and embryo transfer (IVF-ET) treatment: A meta-analysis. Archives of Gynecology and Obstetrics, 298(5), 861-871. Web.