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The notochord is the defining feature (synapomorphy) of chordates, and was present throughout life in many of the earliest chordates. Although the stomochord of hemichordates was once thought to be homologous or from a common lineal origin, it is now viewed as analogous, convergent , or from a different lineal origin. [ 22 ]
The dorsal nerve cord is an anatomical feature found in chordate animals, mainly in the subphyla Vertebrata and Cephalochordata, as well as in 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.
Homeobox protein notochord (NOTO) is a transcription factor [1] encoded by the gene notochord homeobox (NOTO) located on the short arm of chromosome 2 (2p13.2) in humans (Homo sapiens). [2] An ortholog of NOTO is found in the house mouse ( Mus musculus ), among other species, as the gene notochord homeobox ( Noto ) located on chromosome 6 ...
The chorda-mesoderm develops into the notochord. The intermediate mesoderm develops into kidneys and gonads. The paraxial mesoderm develops into cartilage, skeletal muscle, and dermis. The lateral plate mesoderm develops into the circulatory system (including the heart and spleen), the wall of the gut, and wall of the human body. [11]
The notochord plate separates and forms the solid notochord. [4] The folding of the neural tube to form an actual tube does not occur all at once. Instead, it begins approximately at the level of the fourth somite at Carnegie stage 9 (around embryonic day 20 in humans). The lateral edges of the neural plate touch in the midline and join together.
A primary step in organogenesis for chordates is the development of the notochord, which induces the formation of the neural plate, and ultimately the neural tube in vertebrate development. The development of the neural tube will give rise to the brain and spinal cord. [1]
The notochord extends from the base of the head to the tail; with it extend thick bands of paraxial mesoderm. [1] As the primitive streak continues to regress, somites form from the paraxial mesoderm by "budding off" rostrally as somitomeres, or whorls of paraxial mesoderm cells, compact and separate into discrete bodies. The periodic nature of ...
These cell types are specified by the secretion of the Shh from the notochord (located ventrally to the neural tube), and later from the floor plate cells. [6] Shh acts as a morphogen, meaning that it acts in a concentration-dependent manner to specify cell types as it moves further from its source. [7]