Growth of Different Cell Types

Not only do the different parts of the brain grow at different times and at different rates but also there are differences in the timing of multiplication of different cell types within a particular brain region. It has been known for a long time that multiplications of the neurons and of the glia are two consecutive processes, the former being followed by the latter.

While studying the cellular growth of the human brain, Dobbing and Sands observed two distinct peaks of DNA accumulation in the forebrain, the first occurring at 18 weeks of gestation and the second at approximately birth (Fig. 6). The first peak was interpreted as corresponding to the peak of neuronal multiplication and the second to that of glial multiplication. However, it is likely that the adult neuronal population is not achieved at 18 weeks of fetal life; some neurons continue to divide beyond this time, but their number is not significant compared to the number achieved by 18 weeks of gestation. Man is thus a fortuitous species in that his brain neuronal population is established as early as mid-fetal life and

Age (weeks)

Age (weeks)

Figure 5 Changes in the (A) proportions and (B) total amounts of gray (•) and white (O) matter of the developing rat brain (reproduced with permission of International Society for Developmental Neuroscience).

Age (weeks)

Figure 5 Changes in the (A) proportions and (B) total amounts of gray (•) and white (O) matter of the developing rat brain (reproduced with permission of International Society for Developmental Neuroscience).

thus saved from the deleterious effects of even severe nutritional insufficiency in the mother.

Was this article helpful?

0 0
Unraveling Alzheimers Disease

Unraveling Alzheimers Disease

I leave absolutely nothing out! Everything that I learned about Alzheimer’s I share with you. This is the most comprehensive report on Alzheimer’s you will ever read. No stone is left unturned in this comprehensive report.

Get My Free Ebook


Post a comment