Plate 33

Copyright © 1995
to the
"Frontiers in Bioscience"

Early tail bud stage (embryo stage 23)

At the posterior part of the neural tube, notochord, neural tube and mesodermal cells continue to develop from the undifferentiated cells in the tail blastema. Islands of blood start to appear in the heart anlage. The notochord starts to become stiff at this stage as a result of vacuolization of the notochordal cells. This also leads to the lengthening of the notochord and therefore the entire body. The midgut narrows to a slit-like structure as a result of bilateral pressure from the cells in the endodermal yolk sac. The bending of the cephalic structures leads to the bending of the brain which is now separated into prosencephalon, mesencephalon, and rhombencephalon.