The Questions of Developmental Biology

12. The central nervous system and the epidermis
"What is perhaps the most intriguing question of all is whether the brain is powerful
enough to solve the problem of its own creation." So Gregor Eichele (1992) ended a review of
research on mammalian brain development. The construction of an organ that perceives, thinks,
loves, hates, remembers, changes, fools itself, and coordinates our conscious and unconscious
bodily processes is undoubtedly the most challenging of all developmental enigmas. A
combination of genetic, cellular, and organismal approaches is giving us a preliminary
understanding of how the basic anatomy of the brain becomes ordered.
The fates of the vertebrate ectoderm are shown in Figure 12.1. In the past two chapters,
we have seen how the ectoderm is instructed to form the nervous system and the epidermis. A
portion of the dorsal ectoderm is specified to become neural ectoderm, and its cells become
distinguishable by their columnar appearance. This region of the embryo is called the neural
plate. The process by which this tissue forms a neural tube, the rudiment of the central nervous
system, is called neurulation, and an embryo undergoing such changes is called a neurula
(Figure 12.2). The neural tube will form the brain anteriorly and
the spinal cord. This chapter will look at the processes by which
the neural tube and the epidermis arise and acquire their distinctive
patterns.