Flashcards in Cells & Embryology Deck (43):
HOw many weeks post-fertilization does the neural plate begin to form?
What germ layer forms the neural plate?
What cavity is the ectoderm continuous with? The endoderm?
ectoderm continuous with amniotic cavity (above)
endoderm continuous with yolk sac (below)
What structure floors the amniotic cavity in the 3rd week?
By what day does the neural groove and neural folds begin to form?
When do the neural folds approach each other?
When do the neural folds fuse across the midline/form tube which then sinks below surface ectoderm?
What day does the anterior neuropore close?
What day does the posterior neuropore close?
From what germ cell layer are neural crest cells dervied?
Neurons that fall in dorsal root ganglion are what functional and morphological type?
What two cranial nerves derive from placodes? Why?
CN I and CN VIII
special senses different from general sensation
What cavity is continuous with the anterior neuropore?
What cell type is the single layer of ectodermal cells lining the neural tube cavity?
pseudostratified columnar epithelium
Describe how the neural tube goes from being lined by a single cell layer to three cell layers
ependymal layer surrounded by cell free marginal layer
cells in ependymal layer divide until they migrate from central canal guided by radial glial --> form mantle layer
now there is a mantle layer in between ependymal layer and marginal layer
Which cell layer is the precursor of gray matter?
intermediate cell layer (mantle cell layer)
Which cell layer is the precursor of white matter ?
marginal cell layer
What is lined by ependymal cells in the adult
central canal and ventricles
What week is the sulcus limitans formed? What does it separate?
separates alar plate and basal plate
What layer differentiates into the alar and basal plates? When?
intermediate (mantle) cell layer
during 6th week
What is the fate of the alar plate? basal plate?
alar - dorsal horn - sensory
basal - ventral horn - motor
What zone lies between the alar plate and basal plate? What is its fate? function?
intermediate zone - intermediate gray
interneurons connecting sensory with motor neurons
autonomic elements (S&PS)
What comprises the three vesicle stage of the brain? When does this occur?
during 4th week
What comprises the five vesicle stage of the brain? When does this occur?
during 5th week, by 6th week
prosencephalon --> telencephalon & diencephalon
mesencephalon --> mesencephalon
diencephalon --> metencephalon & myelencephalon
By what week is the pontine, cervical and cephalic flexures formed?
by week 6
The telecephalon becomes the __ in adult brain
cerebral hemispheres & basal ganglia
The diencephalon becomes the ___ in adult brain
thalamus, hypothalamus, subthalamus, epithalamus
The mesencephalon becomes the ___ in the adult brain
THe metencephalon becomes the ___ in the adult brain
The myelencephalon becomes the ___ in adult brain
When do we start to see sulci? Gyri?
6 months - sulci
9 months - gyri
What is spina bifida?
failure of the full formation of the vertebrae (bony defect)
What is spina bifida occulta?
neural arch in vertebrae fails to form
doesnt involve underlying neural tissue
usually lumbar spine
hairy patch, small dimple
What is spina bifida aperta?
can occur with meningocele, myelomeningocele, myeloschisis
What is meningocele?
cyst that develops off the dimple seen in occulta
may be filled with CSF but does not occur neural elements
What is myelomeningocele?
elements of the spinal cord, spinal nerves are extravasated into the cyst
occasionally seen with hydrocephalus
What is myeloschisis
folds dont fuse together to form tube
neural plate elements remain continuous with surface ectoderm
What is encephalocele?
bony defect in occipital bone of skull
cyst is formed occasionally with the inclusion of the cerebral hemispheres at posterior pole
What is anencephaly?
anterior neuropore fails to close
middle to caudal part of brainstem and brain fails to develop
brain may be exposed at surface and may simply be covered by a small amount of tissue
condition is not survivable beyond 30 days
What is the metabolic and synthetic region of the neuron?
cell body (soma)
Are inhibitory synapses symmetric or asymmetric?
Are excitatory synapses symmetric or asymmetric?