1 - Introduction

Summary

A definition

Morphogenesis means the beginnings of form and, in the context of biological development, is an ambiguous word: the term may refer either to the structural changes that we observe as embryogenesis proceeds or to the underlying mechanisms that are responsible for them. Provided that we acknowledge these two facets, we can accept the ambiguity and let the context define the meaning. The important aspect of the word is change: morphogenesis is the study of how biological form changes, usually to become more complex, and its domain extends across the living world.

Morphogenesis is the most obvious process of development because it is from their structures that we recognise organs and organisms. It is also the most complex because the genesis of form requires the dynamic coordination of the various activities of a great many cells. To make matters worse, the processes of organogenesis tend to take place inside opaque embryos so that it is usually impossible to observe the events directly. Most morphogenetic research has therefore focussed either on describing the stages of organogenesis using fixed tissue or on showing how the properties of particular cells and the molecules that they synthesise can play a role in tissue formation. Relatively little attention has been paid to integrating the mix of molecular, cellular, tissue and dynamic properties that underly organogenesis.

One reason for this lack of attention is that, because the generation of morphology is poorly understood at the genetic level, many biologists believe that we do not yet have sufficient information to elucidate the principles underlying morphogenesis (e.g. Raff & Kaufman, 1983, p.5).