Normal Brain Developement Flashcards
The neural plate appears on the dorsal aspect of the disk as an area of focal ectodermal proliferation at what week of embryoinic life?
At about 2 weeks of embryonic life
The neural plate invaginates, forming a neural groove at approximatly how many days of gestation?
At approximately 18 days of gestation
The lateral portion of the neural groove then thickens and proliferate, forming elevations called what?
Neural folds
The edges of the neural folds bend medially toward each other, eventually making contact and closing over the top of the neural grove to form what structure?
Neural tube
The proximal two thirds of the neural tube thickens to form what?
The future brain
The caudal one third represents the future spinal cord.
Closure of the neural tube begins in what region?
Hindbrain region
And proceeds in a “zipperlike” fasion towards both ends of the embryo.
After the rostral neuropore closes, three hollow fluid-filled expansions are formed.
What are theses structures?
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
What are the three main flexures that divide the developing brain into cerebrum, cerebellum, and spinal cord?
Midbrain, pontine, and cervical flexures
Immediately after neural tube closure, the superficial ectoderm of each side separates from the underlying neural ectoderm and then closes over it.
This separation of ectodermal from neural tissue is extremely important and is known as what?
Disjunction
Formation and maturation of the brain neocortex is a complex but orderly process that involves what process?
Proliferation, differentation, and migration
The cerebral hemispheres first appear as bilateral outpouchings, or diverticulae of the telencephalon at approximately how many days of gestation?
35 days of gestation
The germinal matrix forms at about how many weeks of gestational age and involutes at about how many weeks?
Forms at about 7 weeks
Involutes at 28 to 30 weeks
Although it persists in the form of focal cell clusters up to 36 through 39 weeks
With the exception of the outer layer, neuro migrate from the germinal matrix to cortex in what sequence?
“inside-out” sequence
Those that will form the deepest cortical layer (layer 6) migrate first, followed by layers 5, 4, 3, and, finally, layer 2.
The migration and layering process occurs how many weeks?
6 to 7 weeks through 24 to 26 weeks, when the full six layered cortex is achieved.
As the cerebral cortex is developing, the commissural fibers connect corresponding areas of the cerebral hemispheres with each other.
Theses commissures develop between approximately how many weeks of gestation?
8 and 17 weeks of gestation
The most important of the commissural fibers cross in the lamina terminalis, the rostral end of the forebrain.
