Glossary in Congenital Malformations
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#Neuroenteric canal: During embryogenesis, the neuroenteric canal
connect the neurotube with the york sac, the structure that later develop into
the midgut. The neuroenteric canal should close during development. A rare
malformation, resulted from persistence of neuroenteric canal will allow the
content of the gut to flow into the spinal central canal and causes infection.
#Neuroenteric cyst: they are rare intraspinal and intracranial
extramedullary cysts lined by epithelium resembling that of the gastrointestinal
tract and are usually located at caudal cervical, and rostral thoracic levels.
#Neuropore closure: Rostral neuropore closes around 22 days of
gestation. Caudal neuropore closes at around 26 days of gestation; the closure
occurs at the level of future somite 31, sacral vertebra 2.
#Neurotube defect: A group of defects, heterogeneous in morphology
and causes, in which the neural tube has usually failed to complete neurulation
and one or more of the neural tube coverings are incomplete.
#Neurulation: The process of formation of the neural plate, the
neural folds, and their closure to form the neural tube is called neuralation.
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Primary neurulation:
It can be divided into 4 spatially and temporarily overlapping stages: neural
plate formation, neural plate shaping, neural plate bending, and closure of the
neural groove.
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Secondary neurulation:
It refers to the formation of the caudal portion of the spinal cord in avian and
mammalian embryos. It occurs at about the time the posterior neuropore closure
and involves canalization of a mass of cells derived from the caudal cell mass.
Two processes occur: formation of the medullary plate and cavitation of the
plate. The lumen formed in the medullary plate by cavitation is always
continuous with the lumen of the neural tube formed by primary neurulation. This
process is variable among individuals. Once the spinal cord is formed the caudal
portion atrophies and form the filum terminale.
#Nodular cortical dysplasia: also known as brain warts. They are nodules (1-2
mm in diameter) of cortical layers II and III protrude through a thin or absent
molecular layer. Neurons of various size are grouped around a radial bundle of
myelinated fibers and a central blood vessel. They are most commonly found in
the frontal lobe near the operculum or at the orbital surface.
#Notochord: an axial stiffening rod extending along the length
of the animal and lying immediately above the alimentary canal and below the
central nervous system. It may persist throughout life, as in lower chordate
animal; or be replaced, either wholly or partially, by a backbone or vertebral
column, as in the higher chordate animal.
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