Chapter 17, Problem 3DQ

Summary Introduction

To review:

The fate of notocord cells in those animals which do not develop nuclei pulposi. Whether these cells undergo degeneration or contribute to other structures of the spine. Is there any molecular factor which will guide the formation of nuclei pulposi. Whether the guidance cues like netrins, slits, etc. also play a role in instructing the coalesence of notochord cells into segmented loci.

Introduction:

The notochord is an important structure of the chordates and perform the essential role in vertebrate development. It is an embryonic midline structure which exist transiently in higher vertebrates and perform important functions. If compared as a tissue, it resembles closely to the cartilage. In some vertebrate clades like primitive fish and lampreys, the notochord persists throughout the life. Whereas in case of most of the higher vertebrates, the notochord becomes ossified in areas of forming vertebrae and contributes to the center of intervertebral discs as a structure, known as nucleus pulposis.