Embryo Development Flashcards
What is the term for neural tube formation?
Neuroulation
What type of cells eventually develop into dorsal root and autonomic NS ganglion cells, adrenal medulla, schwann cells, and satellite cells?
neural crest cells
The ______ develops into the tissue of the CNS.
neural tube
The _____ develops into the ventricular system.
neurocoele
The rostral opening of the neural tube, the rostral _______ closes completely in the middle of the 4th week.
neuropore
The caudal ______ closes about 2 days after the rostral.
neuropore
By the end of three weeks, 2 folks meet to form the neural ______ and a center opening called the _____.
neural tube
neurocoele
At the 3rd week of development, the neural plate forms from a dorsal thickening of _______.
ectoderm
A fatal deformity caused by complete failure of neural tubes to close is called:
anencephaly
With anencephaly, important portions of the _____ do not develop.
Cb
The CNS appears as an open furrow on dorsal surface of head and body with ____.
anencephaly
A severe form of spina bifida is known as:
meningomyelocele
_____ is caused by failure of caudal neuropore to close.
spina bifida
Type I arnold-chiari malformation:
asymptomatic
Spina bifida is frequently accompanied by ____ malformation.
arnold-chiari
Type II arnold-chiari malformation:
accompanies meningomyelocele and often occurs with hydrocephalus
Type III arnold-chiari malformation:
associated with severe neurological defect including encaphalocele
Type IV arnold-chiari malformation:
agenesis of Cb
With Arnold-chiari malformation, what structures are often elongated and pushed down into the foramen magnum?
Cb (tonsils)
and caudal brainstem
What are the symptoms associated with arnold-chiari malformation?
headache fatigue weakness of facial muscles dysphagia dizziness nausea impaired coordination in severe cases: paralysis
Meningomyelocele is frequently accompanied by:
hydrocephalus
Describe spina bifida occulta:
simple defect in closure of vertebrae
area of defect often indicated by tuft of excessive hair
Define meninfocele:
herniation of meningeal membranes
appears as a cystic tumor
no CNS involvement
With spina bifida, the nerve roots and SC along with menigneal coverings are ____.
herniated
How many primary vesicles form as expansions of the neural tube during the 4th week?
3
The primary vesicles that form during the 4th week are:
- prosencephalon
- mesencephalon
- rhomencephalon
The prosescephalon subdivides into:
telencephalon: forms cortex and basal forebrain
diencephalon: forms thalamus and hypothalamus
The mesencephalon remains as a primary vesicle and forms the:
midbrain
The Rhombencephalon subdivides into the:
metencephalon: forms pons and Cb
myelencephalon: forms medulla
The cerebral vesicles are portions of the developing CNS related to:
brainstem and cerebrum
The ventricular system develops from the:
neuralcoele
The two primary vesicles subdivide to form a total of __ secondary vesicles.
5
What is the most common developmental cause of hydrocephalus?
blockage of the cerebral aqueduct
What level are the 2 lateral ventricles formed?
telencephalon
What level is the 3rd ventricle formed?
diencephalon
What level is the 4th ventricle formed?
rostral medulla/pons
What level is the central canal formed?
SC/caudal medulla
What level is the cerebral aqueduct formed?
midbrain
During the 4th week, the ____ forms a groove in the inner wall of the neural tube.
sulcus limitans
The sulcus limitans divides the tube into an ___ plate and a ___ plate.
alar (dorsal)
basal (ventral)
In the SC, the ____ plate is the dorsal horn for sensory fxn.
alar
In the SC, the ____ plate is the ventral horn for motor fxn.
basal
Development of the 4th ventricle in the brainstem causes the alar plate to shift laterally to form the _____.
sensory nuclei
Development of the 4th ventricle in the brainstem causes the _____ nuclei associated with the basal plate to line up most medially with nuclei of mixed nerves in between.
purely motor
What structure undergoes the most dramatic development?
telencephalon (cortex)
The basal part of the telencephalon, adjacent to the diencephalon develop into the ____.
basal ganglia
The part of the cortex that overgrows the diencephalon is called the:
insula
The pattern of growth of the telencephalon structures accounts for its “__“-shaped appearance.
“C” shape
The cells of the neuroepithelium surround the ____ and cause cell proliferation when they undergo mitosis.
neurocoele
The area that undergoes mitosis is known as the:
germinal zone
What are the two types of stem cells that can be identified after early mitosis and what do they become?
nueroblasts: become nerve cells
glioblasts: become glial cells
At some point in the development, neuroblasts become _____ (they can no longer undergo mitosis).
postmitotic
What is the pattern of migration?
central (neurocoele) to superficial
Neurons migrate to the cortex along a path set by _____ cells, which act like scaffolding for the neurons to climb.
radial glial
The ___ cells orient perpendicularly to the surface of the brain so the pattern of migration is away from the seminal center like spokes extending from the hub of a wheel.
radial glial
Neurons of the Cb don’t complete migration until:
4 months post-natal
PNS is myelinated by schwann cells that develop from:
neural crest cells
When does PNS and CNS myelination begin?
4th month of fetal life
When does myelination process complete?
early adulthood
CNS myelination of fibers coincides with the time:
they start to function
Some motor tracts and cortical fibers myelinate by:
1 year
Muscles, bone and dermis develop from:
mesoderm
By the 20th day, ____ form from the mesoderm.
somites
The first somite appears in the ____ region.
cervical
Somite development proceeds in which orientation?
caudally
By the end of the 5th week, there are ___ pairs of somites.
42-44
Name the number of pairs of somites by region:
4 occipital 8 cervical 12 thoracic 5 lumbar 5 sacral 8-10 coccygeal
By the beginning of the 4th week, the cells of the somite most ventral and medial migrate to surround the ____.
notocord
The cells surrounding the notochord that will develop into vertebrae are called the _____.
sclerotome
The somites that do not form the slerotome form the:
myotome
dermatome
From each somite develops:
- bone (from sclerotome)
- muscle (from myotome)
- part of dermis (from dermatome)
When do limb muscles begin to develop near the base of the limb bud?
7th week
Initally, the migration of myotome and dematome forms the limb bud in a ____ fashion.
segmental
As limb bud lengthens, myotomes and dermatomes loose their segmentation and fuse so that individual muscles of the limb are derived from more than one ____.
somite
explains how muscles are enervated by more than one SC level
What accoutns for the mature dermatomal pattern?
- each dermatome associated with specific spinal nerve
2. dermatomes that migrate to the limb bud eventually loose connection with axial portion as the limb bud lengthens
