High-Yield Neuroanatomy 5e

12 Chapter 2
Three primary
vesicles
Five secondary
vesicles
Adult derivatives of:
Walls Cavities
Wall
Cavity
Telencephalon
Cerebral
hemispheres
Lateral
ventricles
Forebrain
(prosencephalon)
Diencephalon
Thalamus
Third
ventricle
Midbrain
(mesencephalon)
Hindbrain
(rhombencephalon)
Mesencephalon
Metencephalon
Myelencephalon
Midbrain
Pons
Cerebellum
Medulla
Cerebral
aqueduct
Upper part of
fourth ventricle
Lower part of
fourth ventricle
Spinal cord
Figure 2-3 The brain vesicles indicating the adult derivatives of their walls and cavities. (Reprinted from Moore
KL. The Developing Human: Clinically Orienting Embryology. 4th ed. Philadelphia, PA: WB Saunders; 1988:380, with
permission.)
III
The Cranial Neuropore—closure of the (cranial anterior) neuropore gives rise
to the lamina terminalis. Failure to close results in anencephaly (i.e., failure of the brain to
develop).
IV The Caudal Neuropore—failure to close results in spina bifida (Figure 2-4).
V
Microglia arise from blood-born monocytes.
VI
Myelination begins in the fourth month of gestation. Myelination of the corticospinal
tracts is not completed until the end of the second postnatal year, when the tracts become
functional. Myelination in the cerebral association cortex continues into the third decade of life.
A. Myelination of the CNS—accomplished by oligodendrocytes.
B. Myelination of the PNS—accomplished by Schwann cells.
VII
The Optic Nerve and Chiasma—derived from the diencephalon.
The optic nerve fibers occupy the choroid fissure. Failure of this fissure to close results in
coloboma iridis.
VIII
The Hypophysis (pituitary gland)—derived from two embryologic
substrata (Figures 2-5 and 2-6).