A human being may live for over a century yet the happenings in the first three months after the formation of the initial human cell are fundamental to the nature and quality of life. It is worthy of notice that during this duration, commonly referred to as the first trimester, humans only grow from microscopic size to only slightly over one inch in size. In spite of the minute size, so much critical and sensitive developments take place within the growing miniature body (Bazin-Lopez et al., 2015). Most of the crucial internal and external body features will develop at this stage. Among the most important and sensitive developments at this stage is the development of miniature eyes which will eventually develop into eyes. At this sensitive segment of pregnancy, what happens to the mother can also lead to some congenital disabilities in the child. For example, a high fever on the mother during this stage can cause congenital facial deformities including a cleft lip or palate. The instant research paper evaluates how the sensitive development processes during the first trimester can lead to eventual normality or abnormality for the child in its future life.
Development of the Eye
The Timing
It is important to note that the initial count for the life of an infant begins long before any life is formed through the fertilization of the ovum by the spermatozoa. Scientifically, the countdown to the 40 weeks gestation period begins on the first day of the last menstruation flow of the mother. Fertilization will take place in the third week and implantation in the fourth, which then paves the way for the commencement of the actual development of the fetus. It is this initial development that informs the bulk of the instant research paper. Between the third week and the sixth week of gestation, the eyes begin to form. This formation and development will continue until approximately the tenth week, which still falls within the first trimester (Bazin-Lopez et al, 2015).
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The Ingredients
Several key and minor ingredients are necessary for the formation and development of the eye. These include the Neuroepithelial cells, the Ectoderm, and the extracellular mesenchyme. The control gene Pax-6 triggers the process of eye formation . The Neuroepithelial cells can be defined as stem cells of the nervous systems and fall into different categories. These cells are the building blocks that are used to form the inner part of the eye, which include the optic nerve, retina, ciliary body, and iris (Bazin-Lopez et al, 2015). The ectoderm, alongside the mesoderm and the endoderm, are the three germ layers of the embryo. The endoderm is the outermost germ layer, followed by the mesoderm with the endoderm being the innermost. The endoderm is the building block that forms the outer parts of the eye including the corneal, lens, epithelium, and eyelid. Finally, the Neuroepithelial cells and the endoderm are the building blocks and extracellular mesenchyme forms secondary and connective tissue in the eye, including the muscles, blood vessels, sclera, the corneal endothelium and stroma, and vitreous (Li et al, 2013).
The Process of Eye Formation
As indicated above, around the third week of gestation, which means when the fertilized egg is still finding its way down the fallopian tube and attempt to attach itself on the uterine wall, the control gene Pax-6 triggers the formation of the eyes. The initial process triggered is the evagination of the outer sulci that is undertaken by the Neuroepithelial cells (Martinez-Moralez et al, 2017) . These two sulci will then develop into the outer optic vesicles. Therefore, the initial section of the eye development involves the development of the neural aspects of the eye. The two sulci, which are in essence extensions of the developing brain will keep growing until they come into contact with the endoderm which will then begin the development of the outer elements of the outer eye. The Neuroepithelial cells and the endoderm for the major parts, the extracellular mesenchyme will be making the secondary, auxiliary and connective tissue as indicated above (Li et al, 2013). All the three ingredients will be working singularly or jointly depending on the specific segments of the development process. The optic vesicles aforementioned will develop into optical cups. At this point, the process of invagination will commence. The invagination will lead to the development of the lens placode and eventually the differentiation of cells until the complete but miniature eye is developed (Martinez-Moralez et al, 2017) . It is worthy of notice that the processes above do not take place in isolation but rather occur contemporaneously with other growth processes. By the tenth week when the human eye is fully formed most other critical commencements have also already taken place, and a high-resolution scan of the baby will reveal it as mainly formed but extremely minute.
Congenital Defect during First Trimester
The research journal article by Sass et al. (2017) reports on a cohort study undertaken to resolve one of the major scientific arguments relating to fever and congenital disabilities in the first trimester of pregnancy. Earlier research had established a close correlation between mothers who have high fever and children born with deformities such as a cleft lip or palate. A section of experts argued that the defects were caused by the infection that also caused t he fever itself. There was, however, a growing hypothesis that it is the high temperature and not the infection per se that was causing the defect. This research dilemma was fundamental because there are some risks of the baby in the first trimester associated with the use of some drugs used to fight fevers leading to the argument that only antibiotics to fight the infection itself should be used . However, the research reported in Sass et al. (2017) revealed that the high fever itself caused the cleft lips or palates. This congenital disability is a consequence of heat-activated transient receptor potential (TRP) ion channels released to prevent hyperthermia. However, these TRPs, which include TRPV1 or TRPV4, cause the embryo to develop a heart problem, a cleft lip, or a cleft palate. It is, therefore, critical that fever be controlled using drugs that are safe for the embryo such as Paracetamol during the first trimester in the case of high fever to prevent the advent of this congenital disability .
The human eye is one of the most complex organs in the body, both in structure and function. Based on the research and analysis above, the initial development of the human eye, all that takes place in the first trimester is equally complex. The process begins even before the embryo reaches the uterus and attaches itself to guarantee the viability of the embryo itself. It will then continue through the working together and in turns with the Neuroepithelial cells, the Ectoderm, and the extracellular mesenchyme through to the tenth week when a miniature eye will have been formed . The process occurs alongside many other developmental processes in the infant. During the pendency of this process, in the case of a high fever, it is possible for the TRPs TRPV1 or TRPV4 to be excreted both of which have been known to cause cleft lips or palates. Therefore, if all goes well in the first trimester, the eyes will form, but a high fever can also cause the congenital disability of a cleft lip or palate.
References
Bazin-Lopez, N., Valdivia, L. E., Wilson, S. W., & Gestri, G. (2015). Watching eyes take shape. Current opinion in genetics & development , 32 , 73-79
Li, B., Moshfegh, C., Lin, Z., Albuschies, J., & Vogel, V. (2013). Mesenchymal stem cells exploit extracellular matrix as mechanotransducer. Scientific Reports , 3 , 2425
Martinez-Moralez, J. R., Cavodeassi, F., & Bovolenta, P. (2017). Coordinated morphogenetic mechanisms shape the vertebrate eye. Frontiers in Neuroscience , 11 , 1-8 doi: 10.3389/fnins.2017.00721
Sass, L., Urhoj, S. K., Kjærgaard, J., Dreier, J. W., Strandberg-Larsen, K., & Andersen, A. M. N. (2017). Fever in pregnancy and the risk of congenital malformations: A cohort study. BMC Pregnancy and Childbirth , 17 (1), 413. doi: 10.1186/s12884-017-1585-0.
