ventral nerve cord

The ventral nerve cord is a key component of the nervous system in many invertebrates, such as arthropods and annelids. It is described as a chain of connected segmental ganglia that lies against the body wall. This structure is characteristic of elongated invertebrates like earthworms.12

In contrast, vertebrates have a dorsal nerve cord, which develops into their central nervous system. The development of the nervous system, including the spinal cord, begins early in embryonic development from a neural plate that forms a neural tube. This tube differentiates into gray and white matter, with dorsal and ventral halves associated with sensory and motor functions, respectively. The notochord, a flexible rod in early vertebrate embryos, plays a role in the organization of nervous system development.234