Fetal Brain Development and the Preterm Infant

The purpose of this article is to highlight the biological processes that drive embryonic development. It will be mainly focused on stages of prenatal development at the semi-cellular level that result in visible advances in the embryo’s development as it matures into a fetus and eventually is born. However, these biological processes are not flawless; in some cases, infections, risk factors present in the environment outside of the uterus, or genetic diseases can pose harm by altering how developmental processes proceed or even result in lethality to the fetus. Genetic diseases and illnesses of high concern will thus be discussed in greater detail, as will proposals to prevent or lower the risk of these events from affecting development.

Between day twenty-five and twenty-seven of pregnancy, normally before a woman even knows she is pregnant, the neural tube that ultimately becomes the brain and spinal cord begins to develop and eventually close. When the neural tube fails to close, the outcome is a neural tube defect called anencephaly.

A common teratogen that causes problems in pregnancy is the use of methamphetamine, a stimulant that affects a person’s central nervous system, by the potential father or mother. Research on methamphetamine abuse among pregnant women is in progress and has been for several years, but the exact effects of prenatal exposure to this drug are still actually limited. It is common for a child of a mother who used meth during pregnancy to have brain development problems. The National Institute on Drug Abuse(NIDA), (2013) informs us that there have been only small samples of pregnant women researched for only using methamphetamine, therefore, the results are limited to knowing that “neurobehavioral problems such

Shortly after an egg is fertilized stem cells begin to form. These cells are programmed to form every organ and tissue in the body as the baby develops.

A. Starting at the epiblast, describe five developmental events leading up to the generation of upper motor neurons that reside in layer 5 of the motor cortex.

The brain continues to grow and rapidly develops in three stages known as Neurogenesis, Synaptogensis, and synaptic pruning. Neurogenesis describes the process of rapid division within the nervous system to create functional regions of the brain where most of the process is complete before birth while some regions continue to form after birth such as hippocampal cells. Synaptogensis forms new connections between neurons as over time connections increase in density where some only form one synapse and others form hundreds of thousands. Synaptic pruning removes synapses due to the fact some are only needed temporarily, some are damaged or become dysfunctional, or that some are not used often enough so they are removed for specialization. The newly formed fetus from weeks 9 to 12 shows signs of simple movement with reflexes in arms and legs while sex organs begin to differentiate. Fingers, fingerprints, and toes are fully formed around week 16 and around week 24 the fetus develops response to sound. More remarkably the brain doubles in size between week 16 and 28, while developing basic behavior. The fetus gains greater coordination skills as the cerebral cortex grows larger and personality also develops. Around the 28th week the fetus can mediate sensory input as thalamic brain connections form, such as responding to bright light from within the dark womb. Growth slows down around the 30th or 32nd week but the fetus continues to gain weight and by week 37 has developed all organ systems necessary to survive outside the uterus. Prenatal development ends with the birth of the fetus around 38 to 40 weeks

2) and in the regulation of zebrafish neurulation by the midline signals. Zebrafish neurulation resembles mammalian secondary neurulation and can be potentially associated with neural tube deffects.

Contained in the human body there are more than 220 different cell types being derived from a group of cells called embryonic stem cells. Being located in what is known as the inner cell mass of a blastocyst which is a young embryo about four to five days old. The uniqueness of these cells and what defines them is that they are pluripotent, meaning they are able to differentiate into any 3 germ layers. These layers include the endoderm, mesoderm, and ectoderm. Being able to

Anencephaly is a neural tube defect (NTD) that happens during embryonic fetal development. The neural tube is a narrow channel in the head and spinal cord. It normally folds and closes between the third and fourth weeks of pregnancy. Anencephaly occurs when the head end of the neural tube (cephalic end) fails to close. This causes a major portion of the brain, skull and scalp not to develop. Infants with this disorder are born without the front part of the brain (forebrain) and the thinking and coordinating part of the brain (cerebrum). The remaining brain tissue is often not covered by bone or skin (exposed).

The development of the brain begins in the first few weeks after conception. Most of the physical features of the brain appear during the embryonic period (about the first 8 weeks after fertilization); these structures then stay to grow and develop during the fetal period (the rest of conception.

In mice, this process starts around Embryonic Day 11.5 as the neural progenitor cells located in the Ventricular and Subventricular Zones (SVZ) migrate upwards to form what will later become Layers 2 through 6. Neurons are formed as these neural progenitor cells become Radial Glial Cells (RGC), a subpopulation of stem cells, and differentiate. The timing of the differentiation determines when neurons will form the lower or upper layers. When the differentiation occurs early in neurogenesis, the neurons migrate slightly to form the lower layers. In later neurogenesis, the differentiated neurons migrate past the lower layers and begin forming the upper layers. The formation of the upper layers tends to arise from differentiation of Intermediate Progenitor Cells (IPCs) rather than RGC differentiation. IPCs are formed from neural progenitor cells alongside RGCs (Kwan et al. 1538). While neurogenesis in humans may lead to differing relative sizes of the layers and SVZ, the structure of six specified layers is the same. The divisions between the layers do not occur in humans until around gestational week 9 to 11 (Deboer et al.

Neuroplasticity is a process. As individuals go through the stages of life, he/she experiences the different stages of neuroplasticity (Nelson, 2011). These stages include prenatal and postnatal events that give rise to human brain functioning. The major prenatal events include neural induction, neurulation, cell proliferation and migration, followed by differentiation, apoptosis, and axonal outgrowth. Myelination and synaptogenesis fall into both categories of prenatal and postnatal (Nelson, 2011).

The neural tube is lined with stem cells and can be divided and help to create other new cells. In the formation of the prenatal brain development are the three main regions which are the hindbrain, midbrain and the forebrain. The hindbrain structure is the first to develop, then the midbrain and the forebrain. The developing brain cells multiply; differentiate and migrate to their final destination. Therefore, neurons are beginning to form the structure of developing nervous system. As the brain developed after birth, the frontal lobe developed voluntary movement, perception, reasoning, attachment and a sense of emotional well-being. As a child reaches 7 to 8 months of age, the increase maturation of the child system reflects the development of the brain as distant objects become clearer. At the age of six, the brain is full of energy and is about 95% of its adult weight. At that stage which is the concrete operational stage, neural or grey matter of pruning and wiring of the brain is still in progress. Fatty tissues around the neurons or the white matter increase the speed of electrical impulses and stabilize connection. Children are more capable of true logical thought but ignore social causes as they have very little or no regards for others but themselves. At the adolescence to maturity, the prefrontal cortex of the brain is the last to develop as it controls impulses and

Before we are born we start developing the brain it is like a tube with swellings which indicate what parts they will turn into as the brain develops starting from the top in a pre birth human mammal the top most bump in the upsidedown u-shaped tube is the forbrain also called prosencephalon that will develop into the cerebal hemispheres he thalamus, and the hypothalamus in mammals.(Merriam-Webster, n.d.) the second part down of the tube is the midbrain that will eventually form the the portion of the brain that lies between the forebrain and hind brain which will develop into thhe tectum and the tegmentum as well as the substantia collectivly called the mesencephalon. Following the next one down (pinnel. N.D). is the hind brain which will

Most neuroblasts mature by birth, though a small number of immature neuroblasts can be found in newborns. In most cases, these neuroblasts mature or disappear. Others, however, form a tumor a neuroblastoma. It isn't clear what causes the initial genetic mutation that leads to neuroblastoma.