The Dorsal Hollow Nerve Cord (DHNC) is a distinctive anatomical feature found in the phylum Chordata, which includes vertebrates (animals with backbones) as well as some non-vertebrate chordates. It is a long, hollow, and flexible tube-like structure that runs along the dorsal (back) side of the body.
During embryonic development, the Dorsal Hollow Nerve Cord forms from a process called neurulation, where a groove called the neural groove appears on the dorsal side of the developing embryo. This groove then folds inward, creating a tube-like structure called the neural tube. In vertebrates, the neural tube eventually differentiates into the brain and spinal cord.
In non-vertebrate chordates (e.g., lancelets and tunicates), the Dorsal Hollow Nerve Cord persists as the main nervous system structure throughout their life stages, serving as a simple but effective central nervous system.
In vertebrates, however, the Dorsal Hollow Nerve Cord undergoes further development and specialization. It eventually differentiates into the brain, which is located in the cranial region, and the spinal cord, which is protected by the vertebral column (backbone) along the body's length.
The Dorsal Hollow Nerve Cord is a defining characteristic of chordates and plays a crucial role in coordinating and transmitting nerve signals throughout the body, controlling various physiological functions and allowing for complex behaviors and movements.