Development Of The Brain Flashcards
The neural plate and neural groove develop on the ____ at week ____. This is induce by the notochord.
Neurulation begins week ___.
Cranial 2/3 of the neural plate become ____ and caudal 1/3 becomes ____.
Posterior aspect of the trilaminar embryo; 3
4
4th pair of somites=future brain
Future SC
The neural tube first forms at the ___.
It proceeds cranially and caudally until the neuropores remain. Cranial neuropore closes at ____ and caudal neuropore closes at ____.
5th somite
25 days; 27 days
SC develops caudal to the ____.
The lateral walls of the neural tube thicken which reduces the size of the ____ until a small ____ exists at week ____.
The neural tube is composed of ____ neuroepithelium.
4th pair of somites
Neural canal; central canal (canals will form the ventricles); 9-10
Pseudostratified columnar
What are the three zones of the neural tube and what cells do they contain?
Ventricular zone: neuroepithelial cells closed to the lumen that will divide and migrate
Intermediate zone: cells that differentiate into neurons and/or glia
Marginal zone: decreased cell bodies that contain axons that will eventually be myelinated
There are five closure sites involved in the formation of the neural tube. Failure of a site to close during week ___ leads to ____.
____ results from the failure of closure of site 2.
____ results from failure of closure of sites 1, 2, 4.
Closure of site 5 occurs via ____.
4; spina bifida cystica
Meroencephaly
Craniorachischisis
Secondary neurulation
Four types of spina bifida?
SB occulta: infused neural (vertebral) arch, skin remains intact
SB with meningocele: meninges extrude
SB with menigomyelocele: meninges and neural tissue extend
SB with myeloschisis: open neural tissue
___ differentiate from neuroepithelial cells. After neuronal formation ceases, glioblasts become ____ and ____.
When glial production stops -> neuroepithelial cells differentiate into ____.
Microglia are derived from ___.
___ controls the proliferation and patterning of neuroepithelial cells via GLI transcription factors.
Glioblasts; astrocytes and oligodendrocytes
Ependymal cells
Mesenchyme
SHH
Differentiation of the SC produces thick walls, but thin roof and floor plates. It produces a shallow longitudinal groove on each side called a ____.
Fx?
Sulcus limitans: separates the alar plate (dorsal) form the basal plate (ventral)
Regional separation of plates has a fundamental importance: each become associated with afferent and efferent functions
Cell bodies in the alar plates form a ____, constitute afferent nuclei and groups of them form the _____.
____ forms with enlargement of alar plates.
Dorsal gray column; dorsal gray horns
Dorsal median septum
Cell bodies in the basal plate form ventral and lateral gray columns. They form the efferent nuclei -> _____.
Axons will grow out to form ____.
As the basal plates enlarge, they bulge ventrally on each side forming ____.
A deep longitudinal groove develops on the ventral surface called ____.
Ventral gray horns and lateral gray horns
Ventral roots of spinal nerves
Ventral median septum
Ventral median fissure
Basal and alar cranial nerve nuclei are organized into seven columns?
- Somatic efferents
- Branchial efferents (special visceral efferents
- General visceral efferents
- General visceral afferents
- Special visceral afferents
- General somatic afferents
- Special somatic afferent
Brian develops during the ___ week from the ____, cranial to the 4th pair of somites.
Fusion of neural folds in cranial region and closure of rostral neuropore form _____.
3rd; neural tube
Primary brain vesicles
During the ____ week, the secondary brain vesicles form.
Forebrain divides into ____.
Midbrain does not divide but becomes the ____.
Hindbrain divides into ____.
5th
Telencephalon: cerebral hemispheres/lateral ventricles
Diencephalon: thalamus/3rd ventricle
Mesencephalon: midbrain/cerebral aqueduct
Metencephalon: pons and cerebellum?upper 4th ventricle
Myelencephalon: medulla/lower 4th ventricle
During the ___ week, the embryonic brain grows rapidly and bends ventrally with the ____.
Bending produces the ____ and ____.
Unequal growth produces the ____ that folds in the opposite direction.
5th; head fold
Midbrain flexure (mesencephalic flexure); cervical flexure (midbrain-SC junction)
Pontine flexure (meten-myelencephalon junction)
Cervical flexure demarcates the ____ from the SC. The junction is defined as the level of the superior rootlet of ____ (foramen magnum).
The pontine flexure divides the hindbrain into the ____ and ____.
Myelencephalon -> _____.
Metencephalon -> ____.
Cavity of hindbrain -> ____ and ____.
Hindbrain; C1
Metencephalon and myelencephalon
Medulla oblongata
Pons and cerebellum
4th ventricle and central canal in medulla
In the caudal myelencephalon, neuroblasts in alar plates migrate into the marginal zone and form the ____ and ____.
_____ consist of the crossing of CST fibers.
Nuceli gracilus and cuneatus
Pyramids
The rostral myelencephalon forms the ______, ______, and _____.
Basal plates become medial to the ____ and motor nuclei develop medially to ___.
Pontine flexure (causes walls of the medulla to move laterally/flatten), roof plate, and cavity (part of the future 4th ventricle)
Alar plates; sensory nuclei
Neuroblasts in the basal plate develop into ____. Nuclei organize into cell columns on each side and contain _____.
Neuroblasts in the alar plate of the medulla form neurons arranged in columns on each side and contain ____.
Some migrate ventrally and form neurons in the ____.
Motor neurons; efferents
Afferents
Olivary nuclei
Metencephalon forms the ____ ventrally and the ____ dorsally.
Cavity of metencephalon forms the superior part of the ____.
The pontine flexure forces walls of the pons laterally -> spreading the gray matter in the floor of the ____.
Neuroblasts in each basal plate develop into ____.
Pons; cerebellum
4th ventricle
4th ventricle
Motor nuclei
Cerebellum develops from the ____.
____ project into the 4th ventricle and fuse in the medial plate.
Then they overgrow the rostral 4th ventricle and overlap the _____.
Dorsal parts of the alar plates
Cerebellar swellings
Pons/medulla.
Neuroblasts of alar plates migrate into the tectum to form the _____ and ____.
Neuroblasts of basal plates form the ____ which include what?
Fibers growing from the cerebral cortex form ____.
The neural canal narrows and forms ____ connecting what?
Superior and inferior colliculi
Tegmental nuclei: red nuclei, reticular nuclei, CN III and IV nuclei
Cerebral peduncles
Cerebral aqueduct: connecting 3rd-4th ventricles
Swellings in the lateral walls of the 3rd ventricle form the diencephalon including the ____, _____, ____.
What does the epithalamus sulcus separate?
What does the hypothalamic sulcus separate?
Thalamus, hypothalamus, and epithalamus
Separates thalamus and epithalamus
Separates thalamus and hypothalamus
The thalamus develops on each side of the ____, bulges into its cavity, and fuses at the midline forming the _____ connecting the two halves.
Hypothalamus arises from ____ in the intermediate zone. Endocrine and homeostatic nuclei develop. ____ form on the ventral surface.
3rd ventricle; interthalamic adhesion
Neruroblasts
Mammillary bodies
Pituitary gland develops from the _____ to become the pars anterior and pars tuberalis. The _____ develops to become the median eminence, infundibulum, and pars nervosa.
The hypophyseal diverticulum lies near the floor of the ____ and forms during the ___ week. Its connection to the oral cavity degenerates during the ____ week.
The infundibulum passes between the developing bones of the ____.
Hypophyseal diverticulum: (Rathke’s pouch) upgrowth of the roof of the stomodeum
Neurohypophyseal diverticulum: downgrowth from diencephalon
Diencephalon; 3rd; 6th
Cranium
The telencephalon splits to contain a median part and two _____ which become the ____.
The medial cavity of the telencephalon forms the anterior ____.
As closure of the rostral neuropore occurs, the ____ appear which become ____.
Communication of the cerebral hemispheres with the 3rd ventricle is via the ____.
Two telencephalon/cerebral vesicles ->cerebral hemispheres
3rd ventricle
Optic vesicles -> retinae and optic N
Interventricular foramina
The medial wall of the cerebral hemisphere becomes thin and is continuous with the roof of the 3rd ventricle to become the ___.
Cerebral hemispheres expand and cover the ____.
The mesenchyme trapped in the longitudinal fissures give rise to the _____.
The cavities of the telencephalon and diencephalon form the ____.
Choroid plexus
Diencephalon, midbrain, hindbrain
Falx cerebri
3rd ventricle
The cerebral hemispheres initially have three zones in the neural tube? What is the 4th layer that appears after?
The proliferating cells of the ____ layer undergo a series of regulated divisions to produce waves of neurons that migrate peripherally, this becomes the ____.
Cortical layers are laid down in a sequence ____.
Ventricular, intermediate, and marginal zones; subventricular zone
Ventricular; neuronal layers of the cortex
Deep to superficial (inside out): neurons migrate through the deeper layer and exit to establish more superficial layers (inside out development)
The 1st neurons from the ventricular zone form a ____ that underlies the developing pia.
The axons extend on the inner side of the preplate and establish the ____.
The next set of neurons migrate into the preplate, split it, and produce the ____.
Preplate
Intermediate zone
Cortical plate: in between the marginal zone and the subplate
Neurons migrate on the processes of the ____ that span the cortex to get to their final destination.
Axons from the neurons in the cortical plate and subplate join those in intermediate zone and will later form the _____ of the cortex.
Early neurons from the deepest layers of the cortex including layers ___.
Radial glial cells
White matter
VI and V
Late neurons migrate through intermediate zone and subplate. They pass through layers _____ and establish layers _____.
What is the subventricular zone?
VI and V
IV -> III -> II
New neurons in an extra germinative layer
Groups of never fibers interconnecting the cerebral hemispheres are _____. The rostral end of the forebrain is the ____.
What two commissures form first?
Cerebral commissure
Lamina terminalis
Anterior commissure: interconnects the olfactory bulb within the hemispheres
Hippocampal commissure: connects the hippocampal formations
_____ forms and links hemispheres.
Lamina terminalis is stretched and forms the ____.
Corpus callosum (anterior portion forms first then posterior)
Septum pellucidum (thin plate of brain tissue containing nerve cells and fibers)
____ is the complete or partial absence of the corpus callosum.
Cause what?
Agensis of corpus callosum
Seizures
____ is the incomplete neuronal migration to cerebral cortex during _____ months of gestation.
What does this cause?
Lissencephaly; 3-4
Pachygyria: broad thick gyri
Agyria: lacks of gyri (smooth surface)
Neuronal heterotopia: cells in aberrant position compared to a normal brain
Enlarged ventricles and malformation of the corpus callosum
Initially appear normal but later develop seizures, mental deficiencies, spastic quadriplegia
____ is a neurodevelopmental disorder where the calvaria and the brain are small but the face is normal sized.
What does it cause?
What causes it?
Microcephaly
Mental deficiencies due to brain underdevelopment.
Low pressure from a reduction in brain growth leads to a small neurocranium
Ionizing radiation, maternal EtOH use, infections agents (cytomegalovirus, rubella virus, toxoplasma Gondi), autosomal recessive
Hydrocephalus is caused by _____.
What causes this?
Impaired production and absorption of CSF -> excess CSF in the ventricular system
Increased CSF by choroid plexus adenoma
Intraventricular hemorrhage causing obstruction of the lateral or median aperture
Congenital aqueductal stenosis
Hydrocephalus results in the dilation of the ventricles ____ to the obstruction, internal accumulation of CSF, and increased pressure on cerebral hemispheres.
What are the two types and what causes them?
Proximal
Obstructive (noncommunicating): ventricles are enlarged
Nonobstructive (communicating): no subarachnoid cisterns or malformation of arachnoid villi
____ is the incomplete separation of the cerebral hemispheres and are associated with facial abnormalities.
Defects in the forebrain development often cause facial anomalies resulting from a reduction of the ____.
Causes what?
What genes are involved?
Holoprosencephaly (HPE)
FNP
Cyclopes, premaxillary agenesis, proboscis, single nostril, hypotelorism, facial clefts
SHH, GLI, IHH, SIX3, TGIF, ZIC, PTCH
_____ is a structural defect of the cerebellum.
Causes what?
What are the two types?
Chiari malformation
Tongue like projection of the medulla of the cerebellum; inferior displacement of the cerebral tonsil through the foramen magnum into the vertebral canal; small posterior cranial fossa; noncommunicating hydrocephalus
Type I: inferior part of the cerebellum herniated through the foramen magnum
Type II (Arnold-Chiari malformation): cerebellar tissue and brainstem herniate through the foramen magnum; accompanied by occipital encephalocele and lumbar myelomenigocele
