GENERAL HISTOLOGY

Detailed explanation-1: -The dorsal hollow nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. This is important, as it distinguishes chordates from other animal phyla, such as Annelids and Arthropods, which have solid, ventral tubes.

Detailed explanation-2: -The dorsal nerve cord is a hollow bundle of nerve fibers that transverse dorsally the longitudinal axis of chordates at some stage of their life, and runs above the notochord and gut. The dorsal nerve cord is an embryonic feature that is unique to chordates.

Detailed explanation-3: -The notochord is a long, rodlike structure that develops dorsal to the gut and ventral to the neural tube. The notochord is composed primarily of a core of glycoproteins, encased in a sheath of collagen fibers wound into two opposing helices. The glycoproteins are stored in vacuolated, turgid cells.