Notochord

Embryology - 19 Apr 2024        Expand to Translate
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Introduction

Human notochordal process and notochordal canal (Carnegie stage 8)

The notochord (axial mesoderm, notochordal process) is the defining structure forming in all chordate embryos (taxonomic rank: phylum Chordata). It is an early forming midline structure in the trilaminar embryo mesoderm layer initially ventral to the ectoderm, then neural plate and finally neural tube. This is a transient embryonic anatomy structure, not existing in the adult, required for patterning the surrounding tissues. The patterning signal secreted by notochord cells is sonic hedgehog (shh). This secreted protein binds to receptors on target cells activating a signaling pathway involved in that tissues differentiation and development. This response appears to be concentration dependent, that is the closer to the notochord the higher the shh concentration.

Thought to have at least 2 early roles in development and later roles in patterning surrounding tissues. 1. Mechanical, influencing the folding of the early embryo; 2. Morphogenic, secreting sonic hedgehog a protein which regulates the development of surrounding tissues (neural plate, somites, endoderm and other organs).

In humans, the notochord forms in week 3, is eventually lost from vertebral regions and contributes to the nucleus pulposus of the intervertebral disc during the formation of the vertebral column.

Links: Lecture - Week 3 | Sonic hedgehog | Week 3 | stage 7 | stage 8 | Epithelial Mesenchymal Transition | Notochord | Development Animation - Notochord | Neural | Axial Skeleton | Musculoskeletal | Gastrulation | Category:Notochord

Some Recent Findings

Notochord secreting sonic hedgehog (shown in white)

Transcriptional profiling of the nucleus pulposus: say yes to notochord"This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord. Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement by non-notochordal cells." Notochord-derived BMP antagonists inhibit endothelial cell generation and network formation "Embryonic blood vessel formation is initially mediated through the sequential differentiation, migration, and assembly of endothelial cells (ECs). ...We have previously shown that the notochord is responsible for the generation and maintenance of the avascular midline and that BMP antagonists expressed by this embryonic tissue, including Noggin and Chordin, can mimic this inhibitory role. Here we report that the notochord suppresses the generation of ECs from the mesoderm both in vivo and in vitro."

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: Notochord <pubmed limit=5>Notochord</pubmed>

Notochord Development

Human Embryo notochordal plate A scanning electron micrograph (SEM) image of the human embryo (stage 8, day 15). The notochordal plate is the initial early transient cellular structure and region lying above the primitive streak, that will later be converted into the notochord.

<mediaplayer width='280' height='360' image="http://php.med.unsw.edu.au/embryology/images/9/91/Notochord_02_icon.jpg">File:Notochord 02.mp4</mediaplayer>

This animation shows the early development of the notochord occurring during week 3 of human development. This is a dorsal view of the embryonic disc, caudal (tail and connecting stalk end) to the bottom and rostral (head end) to the top. The indentations show the location of the cloacal (bottom) and buccopharyngeal (top) membranes. The raised region in the middle of the embryonic disc is the primitive node (Hensen's node). The right hand side of the gastrulating embryonic disc is removed to the midline to show the the position of the initial axial process (purple). As the animation plays the axial process extends rostrally from the primitive node towards the buccopharyngeal membrane, where it stops. A cross-section view above the primitive node is shown in the second animation below. Grey - epiblast forming ectoderm | Yellow - endoderm | Orange - mesderm | Purple - axial process Links: Quicktime version | Development Animation - Notochord

<mediaplayer width='240' height='200' image="http://php.med.unsw.edu.au/embryology/images/1/1e/Notochord_01_icon.jpg">File:Notochord 01.mp4</mediaplayer>

This animation shows the early development of the notochord in relation to the endoderm in the trilaminar embryo. The view is a cross-section showing how the axial process initially is formed, then fused with the endoderm, to finally separate as a midline mesoderm structure. Yellow - endoderm | Purple - axial process Links: Quicktime version | Development Animation - Notochord

Patterning

Neural tube patterning	Somite patterning

Development

Week 8

Vertebra and Spinal cord (Carnegie Stage 22)

Nucleus Pulposus

Molecular Factors

• Sonic hedgehog | OMIM - SONIC HEDGEHOG; SHH
• OMIM - T BRACHYURY

Abnormalities

Abnormalities include remnants of notochord that fail to regress. Locations can be along the embryonic path of the notochord and include: ecchordosis physaliphora, odontoid process of the axis, and in the coccyx. Less common locations are in the nasopharynx (Tornwaldt's cysts).

Tornwaldt's cysts

A rare nasopharyngeal lesion occurring in humans thought to develop from remnants of the embryonic notochord adjacent with the embryonic foregut. These cysts are covered by the nasopharynx mucous membrane. Named after Gustav Ludwig Tornwaldt (1843 - 1910) a German physician, the name is also spelled Thornwaldt.

References

Reviews

<pubmed></pubmed> <pubmed></pubmed> <pubmed>21967331</pubmed> <pubmed>20568241</pubmed>

Articles

<pubmed>20565707</pubmed> <pubmed>20041163</pubmed> <pubmed>19997509</pubmed> <pubmed>18629866</pubmed>

Search PubMed

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

Search Pubmed: Notochord

Additional Images

Historic

• 

  Where Remnants of the Notochord may occur in the Adult.

External Links

• OMIM SONIC HEDGEHOG; SHH | T BRACHYURY

Glossary Links

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Cite this page: Hill, M.A. (2024, April 19) Embryology Notochord. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Notochord

What Links Here?

© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G