Dorsal nerve cord
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The dorsal nerve cord is an anatomical feature found in
Vertebrata, as well as some hemichordates. It is one of the five embryonic features unique to all chordates, the other four being a notochord, a post-anal tail, an endostyle, and pharyngeal slits
.
The dorsal nerve cord is located ventral to the gut tube and often separated into a ladder-like series of segmental ganglia. The process by which neural tube is performed from the ectoderm is called neurulation. The evolutionary explanation to this adaptation from a solid cord to a hollow tube is unknown.
In vertebrates, the dorsal nerve cord (and the subsequent neural tube) gives rise to the
Terminologies
The word "
embryological nomenclatures, "dorsal" refers to structures more towards the side of the embryonic epiblast, and "ventral" more towards the hypoblast
side, regardless of the organism's posture and physical orientation.
Other terms such as "
posterior", "front", "back" and so on are body relative directions that are also often used, sometimes to describe a ventral-dorsal relationship among an organism's structures. Such terms are based on an frame of reference
of where the subject is facing, and their meanings are dependent on the organism's current posture and orientation.
- In upright posture, "dorsal" is often synonymous with "posterior", "back" or "rear", and "ventral" with "anterior" or "front", in reference to the direct the organism is facing.[2]
- In
See also
- Ventral nerve cord in some invertebrates
- echinodermata, Xenoturbella and ctenophora
- Hemichordates, who have both dorsal and ventral cords
- Anatomical terms of location
References
- ISBN 9780078023026.)
{{cite book}}: CS1 maint: numeric names: authors list (link - ISBN 9780321918949.
- ISBN 9780323359221.