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Red: notochord; Magenta: axochord; Green: nerve chord; Blue: epidermis; Yellow: mesoderm. The notochord is an elastic, rod-like structure found in chordates. In chordate vertebrates the notochord is an embryonic structure that disintegrates, as the vertebrae develop, to become the nucleus pulposus in the intervertebral discs of the vertebral ...
A key event is when the notochord associated with the tail fin on the ventral side of the spinal cord develops flexion (becomes flexible). The larval stage can be further subdivided into preflexion, flexion, and postflexion stages.
Notochord flexion occurs at around 4 mm standard length in R. loricata. [1] Species. The currently recognized species in this genus are: [2]
The notochord plays an integral role in the development of the neural tube. Prior to neurulation, during the migration of epiblastic endoderm cells towards the hypoblastic endoderm, the notochordal process opens into an arch termed the notochordal plate and attaches overlying neuroepithelium of the neural plate. The notochordal plate then ...
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
Lampreys contain these characteristics that define them as chordates. Lamprey anatomy is very different based on what stage of development they are in. [80] The notochord is derived from the mesoderm and is one of the defining characteristics of a chordate. The notochord provides signaling and mechanical cues to help the organism when swimming.
HNF-3 is needed for development of the notochord and node. [14] The gene Apolipoprotein B, which is involved in transporting and metabolizing fat soluble molecules in the blood, is expressed in the yolk sac and fetal liver. [6] Within the neurula in Xenopus laevis, development genes Xwnt-3 and Xwnt-4 are present. [15]
Both Shh and HNF-3b transcripts are found in the notochord and the floor plate rostral to the node, and they are completely absent in the lateral and caudal neural plate and the primitive streak. In the node proper, the chordin expression pattern is very similar to that of HNF-3b, but more rostrally, chordin is no longer expressed in the floor ...