Neural System - Fetal

Embryology - 5 Dec 2023        Expand to Translate
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Introduction

Human Fetus (CRL 240 mm) Brain (scale bar 1 cm)

Fetal Brain Fissure Development

During the fetal period there is ongoing growth in size, weight and surface area of the brain and spinal cord. Microscopically there is ongoing: cell migration, extension of processes, cell death and glial cell development.

Cortical maturation (sulcation and gyration) and vascularization of the lateral surface of the brain starts with the insular cortex (insula, insulary cortex or insular lobe) region occurs during the fetal period. This cerebral cortex region in the adult brain lies deep within the lateral sulcus between the temporal lobe and the parietal lobe.

This long development time generates the most complex structure within the embryo and the long time period of development means in utero insult during pregnancy may have consequences to development of the nervous system.

| neural crest | Sensory System Development | Second Trimester | Third Trimester | Category:Fetal

Some Recent Findings

Brain growth in the NICU: critical periods of tissue-specific expansion "Utilizing serial MRI to document early brain development in VPT infants, this study documents regional differences in brain growth trajectories ex utero during the period corresponding to the first and second half of the third trimester, providing novel insight into the maturational vulnerability of the rapidly expanding cortical gray matter in the NICU." Exploring the role of white matter connectivity in cortex maturation"We report that the advancement of GM and WM maturation are inter-related and depend on the underlying brain connectivity architecture. Particularly, GM regions and their incident WM connections show corresponding maturation levels, which is also observed for GM regions connected through a WM tract. Based on these observations, we propose a simple computational model supporting a key role for the connectome in propagating maturation signals sequentially from external stimuli, through primary sensory structures to higher order functional cortices." The Lateral Temporal Lobe in Early Human Life "Abnormalities of lateral temporal lobe development are associated with a spectrum of genetic and environmental pathologic processes, but more normative data are needed for a better understanding of gyrification in this brain region. Here, we begin to establish guidelines for the analysis of the lateral temporal lobe in humans in early life. We present quantitative methods for measuring gyrification at autopsy using photographs of the gross brain and simple computer-based quantitative tools in a cohort of 28 brains ranging in age from 27 to 70 postconceptional weeks (end of infancy). ...Analysis of 2 brains with gyral disorders of the lateral temporal lobe demonstrated proof-of-principle that the proposed methods are of diagnostic value. These guidelines are proposed for assessments of temporal lobe pathology in pediatric brains in early life."

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Fetal Neural Development <pubmed limit=5>Fetal Neural Development</pubmed>

Older papers

Local tissue growth patterns underlying normal fetal human brain gyrification quantified in utero "We applied recent advances in fetal MRI motion correction and computational image analysis techniques to 40 normal fetal human brains covering a period of primary sulcal formation (20-28 gestational weeks). ...We detected increased local relative growth rates in the formation of the precentral and postcentral gyri, right superior temporal gyrus, and opercula, which differentiated between the constant growth rate in underlying cerebral mantle and the accelerating rate in the cortical plate undergoing folding. Analysis focused on the cortical plate revealed greater volume increases in parietal and occipital regions compared to the frontal lobe. Cortical plate growth patterns constrained to narrower age ranges showed that gyrification, reflected by greater growth rates, was more pronounced after 24 gestational weeks. Local hemispheric volume asymmetry was located in the posterior peri-Sylvian area associated with structural lateralization in the mature brain. These maps of fetal brain growth patterns construct a spatially specific baseline of developmental biomarkers with which to correlate abnormal development in the human." Development of fetal brain sulci and gyri: assessment through two and three-dimensional ultrasound and magnetic resonance imaging

Human Neural Timeline

Timeline of events in Normal Human Neural Development

Fetal - Second Trimester

Brain and Ventricular Development	Brain Fissure Development

Three months (median sagittal section)	Four months (inferior surface)	Five months (outer surface)

PMID 3339373

At about 19 weeks (GA 21 weeks) neuronal migration ends and the radial glial cells that aided the migration now become transformed into astrocytes and astrocytic precursors.

Fetal - Third Trimester

Human Fetus (CRL 240 mm) Brain (scale bar 1 cm)

Three-dimensional magnetic resonance imaging and image-processing algorithms have been used to quantitate between 29-41 weeks volumes of: total brain, cerebral gray matter, unmyelinated white matter, myelinated, and cerebrospinal fluid (grey matter- mainly neuronal cell bodies; white matter- mainly neural processes and glia).

A study of 78 premature and mature newborns showed that total brain tissue volume increased linearly over this period at a rate of 22 ml/week. Total grey matter also showed a linear increase in relative intracranial volume of approximately 1.4% or 15 ml/week. The rapid increase in total grey matter is mainly due to a fourfold increase in cortical grey matter. Quantification of extracerebral and intraventricular CSF was found to change only minimally.

Cortical surfaces for neonates at 28, 36 and 44 weeks PMA at scan with the labels overlaid.

• 

  28 weeks PMA

• 

  36 weeks PMA

• 

  44 weeks PMA

Thyroid System and Neural Development

Timeline of human thyroid system and brain development from conception to birth. (Estimation of neurogenesis adapted from Bayer et al.)

Links: thyroid

Sulcation and Gyration

Cortical maturation (sulcation and gyration) and vascularization of the lateral surface of the brain starts with the insular cortex (insula, insulary cortex or insular lobe) region during the fetal period. This cerebral cortex region in the adult brain lies deep within the lateral sulcus between the temporal lobe and the parietal lobe.

• sulcation - The process of brain growth in the second to third trimester which forms sulci, grooves or folds visible on fetal brain surface as gyri grow (gyration). Abnormalities of these processes can lead to a smooth brain (lissencephaly).
• gyration - The development of surface folds on the brain (singular, gyrus)

Insular Gyral and Sulcal Development

• 13-17 gestational weeks - appearance of the first sulcus
• 18-19 gestational weeks - development of the periinsular sulci
• 20-22 gestational weeks - central sulci and opercularization of the insula
• 24-26 gestational weeks - covering of the posterior insula
• 27-28 gestational weeks - closure of the laeteral sulcus (Sylvian fissure or lateral fissure)

(Data from: Afif A, etal., 2007)

Three-dimensional magnetic resonance imaging and image-processing algorithms have been used to quantitate between 29-41 weeks volumes of: total brain, cerebral gray matter, unmyelinated white matter, myelinated, and cerebrospinal fluid (grey matter- mainly neuronal cell bodies; white matter- mainly neural processes and glia). A study of 78 premature and mature newborns showed that total brain tissue volume increased linearly over this period at a rate of 22 ml/week. Total grey matter also showed a linear increase in relative intracranial volume of approximately 1.4% or 15 ml/week. The rapid increase in total grey matter is mainly due to a fourfold increase in cortical grey matter. Quantification of extracerebral and intraventricular CSF was found to change only minimally.

(Text - modified from Huppi etal., (1998) Quantitative magnetic resonance imaging of brain development in premature and mature newborns. Ann Neurol 43(2):224-235.)

Neural development will continue after birth with substantial growth, death and reorganization occuring during the postnatal period.

Links: Neuroscience - Regional specification of the developing brain

References

Journals

• Neural Development Browse contents
• Developmental Brain Research Content Listing
• Neural Development Welcome to Neural Development | Pubmed Central Volume 1 2006 | Pubmed Central Volume 2 2007 |
• International Journal for Developmental Neuroscience Official Journal of the International Society for Developmental Neuroscience |
• Developmental Neuroscience Journal Homepage | Hippocampal Development | Vol. 29, No. 3, 2007 |
• Neuroscience Official journal of The International Brain Research Organisation (IBRO)
• Neuron Neuroscience journal published by Cell press

Online Textbooks

Developmental Biology (6th ed) Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000. Formation of the Neural Tube | Differentiation of the Neural Tube | Tissue Architecture of the Central Nervous System | Neuronal Types | Snapshot Summary: Central Nervous System and Epidermis

Neuroscience Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark. Sunderland (MA): Sinauer Associates, Inc. ; c2001 Early Brain Development | Construction of Neural Circuits | Modification of Brain Circuits as a Result of Experience

Molecular Biology of the Cell (4th Edn) Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter. New York: Garland Publishing; 2002. Neural Development | The three phases of neural development

Health Services/Technology Assessment Text (HSTAT) Bethesda (MD): National Library of Medicine (US), 2003 Oct. Developmental Disorders Associated with Failure to Thrive

Search NLM Online Textbooks- "neural development" : Developmental Biology | The Cell- A molecular Approach | Molecular Biology of the Cell | Endocrinology

Reviews

Götz M & Huttner WB. (2005). The cell biology of neurogenesis. Nat. Rev. Mol. Cell Biol. , 6, 777-88. PMID: 16314867 DOI.

Greene ND & Copp AJ. (2009). Development of the vertebrate central nervous system: formation of the neural tube. Prenat. Diagn. , 29, 303-11. PMID: 19206138 DOI.

Articles

Saitsu H & Shiota K. (2008). Involvement of the axially condensed tail bud mesenchyme in normal and abnormal human posterior neural tube development. Congenit Anom (Kyoto) , 48, 1-6. PMID: 18230116 DOI.

Search PubMed

Search Pubmed: Fetal Brain Development | Fetal Spinal Cord Development | Fetal Neural Development

External Links

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• BrainSpan - Reference Atlases 15 pcw - Whole Brain, 21 pcw - Cerebrum, 21 pcw - Brainstem and 34 yrs - Whole Brain.

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Cite this page: Hill, M.A. (2023, December 5) Embryology Neural System - Fetal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_System_-_Fetal

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G