Neural - Spinal Cord Development
Embryology - 10 Jun 2024 Expand to Translate |
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Introduction
Neural development is one of the earliest systems to begin and the last to be completed after birth. This development 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.
The early central nervous system begins as a simple neural plate that folds to form a groove then tube, open initially at each end. Failure of these opening to close contributes a major class of neural abnormalities (neural tube defects).
Within the neural tube stem cells generate the 2 major classes of cells that make the majority of the nervous system : neurons and glia. Both these classes of cells differentiate into many different types generated with highly specialized functions and shapes. This section covers the establishment of neural populations, the inductive influences of surrounding tissues and the sequential generation of neurons establishing the layered structure seen in the brain and spinal cord.
- Neural development beginnings quite early, therefore also look at notes covering Week 3- neural tube and Week 4-early nervous system.
- Development of the neural crest and sensory systems (hearing/vision/smell) are only introduced in these notes and are covered in other notes sections.
Some Recent Findings
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More recent papers |
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This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Spinal Cord Embryology <pubmed limit=5>Spinal Cord Embryology</pubmed> |
Neural Development Overview
Neuralation begins at the trilaminar embryo with formation of the notochord and somites, both of which underly the ectoderm and do not contribute to the nervous system, but are involved with patterning its initial formation. The central portion of the ectoderm then forms the neural plate that folds to form the neural tube, that will eventually form the entire central nervous system.
- Early developmental sequence: Epiblast - Ectoderm - Neural Plate - Neural groove and Neural Crest - Neural Tube and Neural Crest
Neural Tube | Primary Vesicles | Secondary Vesicles | Adult Structures |
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week 3 | week 4 | week 5 | adult |
prosencephalon (forebrain) | telencephalon | Rhinencephalon, Amygdala, hippocampus, cerebrum (cortex), hypothalamus, pituitary | Basal Ganglia, lateral ventricles | |
diencephalon | epithalamus, thalamus, Subthalamus, pineal, posterior commissure, pretectum, third ventricle | ||
mesencephalon (midbrain) | mesencephalon | tectum, Cerebral peduncle, cerebral aqueduct, pons | |
rhombencephalon (hindbrain) | metencephalon | cerebellum | |
myelencephalon | medulla oblongata, isthmus | ||
spinal cord, pyramidal decussation, central canal |
Early Brain Vesicles
In week 3, the neural plate forms and the caudal end of the neural plate remains narrow compared to the cranial end which rapidly expands.
In week 4, when the plate folds to form the neural tube, the cranial end of the tube then forms a series of enlarged cavities (vesicles) that will eventually form the brain. The caudal end of the tube forms a narrower tube of relatively the same size along its length that will eventually form the spinal cord.
Primary Vesicles | Secondary Vesicles |
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early embryonic | late embryonic |
Direct comparison of brain growth embryonic and fetal period. Note the relative size of the spinal cord seen at the lower end of each image.
Spinal Cord Regions
The neural tube forms similar regions around the wall along its length, including the spinal cord. The floor and roof plate are specialised developmental regions, important embryonic "patterning" regions.[4]
- Floor plate - thin wall region that overlies the notochord. Ventral patterns the spinal cord, both floor plate and notochord produce Sonic hedgehog (Shh) (see also Notochord)
- Basal plate - thick wall region lying either side of the floor floor plate. The ventral horn motor neurons develop here and extend axons out of the spinal cord to innervate developing skeletal muscle. Tracts formed by axons surround these horns and project both up and down the spinal cord.
- Alar plate - thick wall region lying either side of the roof floor plate. The sensory dorsal horn develops there and receives axons from the sensory structures outside the spinal cord. The adult horn is divided into 6 laminae (I to VI). Tracts formed by axons surround these horns and project both up and down the spinal cord.
- Roof plate - thin wall region that underlies the dorsal ectoderm epithelium. Dorsal patterns the spinal cord, the roof plate produces Bone morphogenetic proteins (BMPs). [5][6]
- Lumen - neuroepithelium lined fluid-filled space continuous with the brain ventricular system.
Week 4 | Week 8 |
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Stage 13 Spinal cord cross-section (upper part of cord). labeled image | unlabeled image | Stage 22 Spinal cord cross-section (ventral is at top of image) labeled image | unlabeled image |
Embryonic Development
Week 8
Vertebra and Spinal cord (Carnegie Stage 22)
Plexus Development
The spinal nerves initially leave the spinal cord at each individual segmental levels. At various levels they then form an intersecting network of nerves, a plexus, from which mixed segmental nerves emerge.
Cervical Plexus
Brachial Plexus
- Search PubMed: brachial plexus embryology
Lumbar Plexus
- Search PubMed: lumbar plexus embryology
Sacral Plexus
Dermatomes
A dermatome represents the area of skin that is mainly supplied by a single spinal nerve. Therefore each spinal nerve can be "mapped" to a region of the external body surface and that this "map" is established before embryonic limb rotation.
Spinal Cord Histology
Identify gray and white matter, central canal (surrounded by ependymal cells), dorsal and ventral horns, meninges (pia, arachnoid and dura mater), subarachnoid space with dorsal and ventral rootlets, blood vessels, a motor neurone with a cell body (soma), nucleus, nucleolus, Nissl granules, an axon with axon hillock area, dendrites, glial cells (oligodendrocytes, astrocytes).
Spinal cord (Luxol Fast Blue) | |
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Spinal cord - Grey and white matter | |
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Spinal cord - Grey matter | |
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Grey matter (HE) |
Grey matter (silver) |
- Spinal Cord: Overview 1 | Overview 2 | Overview animation | Grey matter | Grey matter | Grey matter | White matter | Overview unlabeled | Grey matter unlabeled 1 | Grey matter unlabeled 2 | White matter unlabeled 1 | Ependymal cells unlabeled
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<mediaplayer width='600' height='230' image="http://php.med.unsw.edu.au/embryology/images/5/5f/Mouse_ependymal_cilia_01-icon.jpg">File:Mouse_ependymal_cilia_01.mp4</mediaplayer> |
Additional Images
Historic
Human Embryology And Morphology (1921) |
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Keith, A. Human Embryology And Morphology (1921) Longmans, Green & Co.:New York.
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References
Reviews
<pubmed>19206138</pubmed> <pubmed>19681160</pubmed> <pubmed>19651305</pubmed> <pubmed>18621990</pubmed> <pubmed>18494249</pubmed> <pubmed>16971596</pubmed> <pubmed>17032846</pubmed> <pubmed>15806586</pubmed> <pubmed>15738958</pubmed>
Articles
<pubmed>18230116</pubmed>
Books
- Bayer S.A and Altman J. The Spinal Cord from Gestational Week 4 to the 4th Postnatal Month CRC Press 2002 Print ISBN: 978-0-8493-1420-9 eBook ISBN: 978-1-4200-4018-0 http://www.crcnetbase.com/doi/book/10.1201/9781420040180
Search PubMed
November 2010 search "Spinal Cord Embryology" All (7631) Review (641) Free Full Text (1562)
Search Pubmed: Spinal Cord Embryology | Spinal Cord Development
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