DEVELOPMENT OF NORMAL PLACENTAL STRUCTURE AND FUNCTION The normal placenta is far more than a mere conduit for nutrient and waste exchange between the mother and fetus. Rather, it is a highly specialized organ with multiple complex and interrelated functions,…
INTRODUCTION Evaluation of the fetal brain is, for obvious reasons, heavily dependent on specialized imaging techniques that have entered the clinical domain over the past five decades. Since its entry into the clinical domain in the late 1960s and early…
Myelination is characterized by the acquisition of the highly specialized myelin membrane around axons. The time period of myelination in the human is long, beginning mainly in the second trimester of pregnancy and continuing into adult life. Myelination in the…
NORMAL DEVELOPMENT Organizational events occur in a peak time period from approximately the fifth month of gestation to several years after birth. However, these complex processes may continue for many more years in human cerebrum. The major developmental features include…
MIGRATION As progenitor cells proliferate and differentiate into neurons and glia (see Chapter 5 ), these cells migrate to form the cerebral cortex in an elaborate and still not completely understood series of genetically influenced processes. Neurodevelopmental studies and disorders…
The awesome complexity of the human brain begins its evolution after the essential external form is established by the events described in Chapters 1 and 2 . The events that follow are proliferation of the brain’s total complement of neurons,…
As is the case for development of the prosencephalic structures discussed in Chapter 2 , the most critical time for development of the form and cellular structure of the brainstem and cerebellum is in the second and third months of…
Introduction The terms ventriculomegaly and hydrocephalus are often used inconsistently and imprecisely in the literature. In this discussion we use ventriculomegaly (VM) as an overarching term to describe enlarged cerebral ventricles without reference to etiopathogenesis, natural history, or outcome. Ventriculomegaly…
Normal Prosencephalic Development The major event following neurulation is development of the prosencephalon, which results in the fundamental structure of the central nervous system. The prosencephalon lies rostral to the other major vesicles of the brain—that is, the midbrain (mesencephalon)…
Introduction An understanding of the development of the nervous system is essential for an understanding of fetal and neonatal neurology. An obvious reason for this contention is the wide variety of disturbances of neural development that are flagrantly apparent in…