Development of the CNS Flashcards
When does the brain begin to develop?
during the 3rd week of development
from what does the brain develop?
the neural tube
what is the stopping point of brain development?
4th pair of somites
what forms the primary vesicles?
fusion of neural folds in the cranial region and closure of the rostral neuropore
how many primary vesicles are there?
3
what are the three primary vesicles?
prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)
what does the forebrain further develop into?
the telencephalon and the diencephalon
what does the midbrain further develop into?
mesencephalon
what does the hindbrain further develop into?
the metencephalon and myelencephalon
when do the secondary vesicles form?
during the 5th week of development
what do the walls of the telencephalon later become?
cerebral hemispheres
what does the cavity of the telencephalon later become?
the lateral ventricles
what do the walls of the diencephalon later become?
thalamus, hypothalamus, epithalamus, and subthalamus
what does the cavity of the diencephalon become?
the third ventricle
what do the walls of the mesencephalon become?
the midbrain
what does the cavity of the mesencephalon become?
the aqueduct
what do the walls of the metencephalon later become?
the pons and the cerebellum
what does the cavity of the metencephalon later become?
the upper part of the 4th ventricle
what do the walls of the myelencephalon later become?
the medulla
what does the cavity of the myelencephalon later become?
the lower part of the 4th ventricle
what are the two ventral brain flexures?
midbrain flexure and cervical flexure
what is the one dorsal brain flexure?
pontine flexure
when do flexures form?
as the primary vesicles transition into the secondary vesicles (5th week of development)
what demarcates the hindbrain from the spinal cord?
the cervical flexure
what demarcates the metencephalon from the myelencephalon?
the pontine flexure
in the caudal myelencephalon, where do neuroblasts in the alar plates migrate to?
to the marginal zone
neuroblasts in the alar plates that migrate to the marginal zone become what?
nucleus gracilis and nucleus cuneatus
what is associated with the nucleus gracilis and nucleus cuneatus?
the pathway that is responsible for processing proprioceptive information –> PCML
what is found in the basal plates of the caudal myelencephalon?
pyramids
what do the pyramids consist of?
white matter tracts for the corticospinal pathway (motor)
what is the structure like of the rostral myelencephalon?
it is wide and flat
what causes the myelencephalon to be wide and flat?
the pontine flexure causes the walls of the medulla to move laterally
what happens to the roof plate of the rostral myelencephalon?
it becomes greatly thinned
what is the positioning of the alar and basal plates in the rostral myelencephalon?
the alar plates are lateral to the basal plates
neuroblasts in the basal plate of the medulla develop into what?
motor neurons
motor neurons that developed from neuroblasts in the basal plate of the medulla organize their nuclei into what cell columns?
general somatic efferent, special visceral efferent, and general visceral efferent
neuroblasts in the alar plates of the medulla form neurons that are arranged in what columns?
general visceral afferent, special visceral afferent, general somatic afferent, and special somatic afferent
some neuroblasts from the alar plates of the medulla migrate more ventrally compared to the afferent columns and they form neurons in what region?
olivary nuclei
What forces the walls of the pons to move laterally?
the pontine flexure
what happens when the pontine flexure forces the pons to move laterally?
it spreads the gray matter in the floor of the 4th ventricle
What does the cerebellum develop from?
the dorsal part of the alar plates
Besides the cerebellum, what also develops from the alar plates of the metencephalon?
central nuclei, pontine, cochlear nuclei
what is the term for when you have pia mater + ependymal roof?
tela choroidea
neuroblasts from the alar plates of the midbrain migrate into what?
the tectum
what is formed when neuroblasts from the alar plates of the midbrain migrate into the tectum?
the superior and inferior colliculi
what do neuroblasts from the basal plate of the midbrain form?
the tegmental nuclei
what makes up the tegmental nuclei?
red nuclei, reticular nuclei, CN III, CN IV nuclei
what connects the 3rd ventricle to the 4th?
the cerebral aqueduct
what do fibers growing from the cerebral cortex form in the midbrain?
the cerebral peduncles (crus cerebri)
what are the thalamus, hypothalamus, and epithalamus form from?
swellings (3) in the lateral walls of the 3rd ventricle
what does the pineal gland develop from?
as a median outgrowth of the roof of the diencephalon
what does the hypothalamus arise from?
neuroblasts in the intermediate zone in the lateral wall of the 3rd ventricle
what forms on the ventral surface of the hypothalamus?
mammillary bodies
what does the epithalamus develop from?
the roof and dorsal portion of the lateral wall
What are the two embryonic sources of the pituitary gland?
hypophyseal diverticulum and neurohypophyseal diverticulum
what is the hypophyseal diverticulum?
an upgrowth of the roof of the stomodeum (oral ectoderm)
what is the neurohypophyseal diverticulum?
a down growth of the diencephalon (neuro ectoderm)
when does the hypophyseal diverticulum project from the roof of the stomodeum?
by the 3rd week of development
when does the hypophyseal diverticulum pass through the cranium and contact the infundibulum?
the 5th week
when does the hypophyseal diverticulum regress from the oral cavity?
6th week
what gives rise to the falx cerebri?
mesenchyme trapped in longitudinal fissure
When does the corpus striatum appear?
in the 6th week
What is the diagnosis for an incomplete separation of the cerebral hemispheres
holoprosencephaly (HPE)
what are the group of nerve fibers interconnecting the cerebral hemispheres known as?
cerebral commissures
What is the initial commissure that forms?
lamina terminalis
where does the lamina terminalis lie?
extends from the roof of the diencephalon to the optic chiasm
which commissure interconnects the temporal lobes with in each hemisphere?
the anterior commissure
which commissure interconnects the hippcampi within each hemisphere?
the hippocampal commissure
what is the condition where there is incomplete neuronal migration during 3-4 months of gestation; smooth cerebral surface?
lissencephaly
What causes microcephaly?
autosomal recessive, ionizing radiation, Zika virus, maternal alcohol abuse
How do you get an interthalamic adhesion?
when the thalamus fuses at the midline (~70%)
what is the connecting stalk of the neurohypophyseal diverticulum?
the infundibulum
What are the basal nuclei collectively referred to as?
corpus striatum
What does the corpus striatum separate into?
the caudate nucleus, the putamen, and the globus pallidus nuclei
What is the key underlying regulator in holoprosencephaly?
SHH
What is the largest commissure that forms from the lamina terminalis?
the corpus callosum
What does the portion of the lamina terminalis that remains form?
the septum pellucidum
