Development of the Brain Flashcards
The neural plate and neural groove develop on the posterior aspect of the trilaminer embryo beginning at 3 weeks. They are induced by the ______
The process of neurulation begins during the ____ week. The cranial 2/3 of the neural plate (4th pair of somites) becomes the future _______. The caudal 1/3 of the neural plate becomes the future _______
Notochord
4th; brain; spinal cord
The _____ _____ first forms at the 5th somite. Fusion proceeds cranially to caudally until only the cranial and caudal _______ remain, the former closes several days before the latter
Neural tube; neuropores
Describe epithelium of neural tube
Pseudostratified columnar neuroepithelium
The SC develops caudal to the 4th pair of somites. The lateral walls of the NT thicken, reducing the size of the neural canal until only a small ____ ____ exists (9-10 wks)
Central canal
3 defined zones of the developing SC
Ventricular zone = neuroepithelial cells closest to the lumen, will divide and migrate
Intermediate zone = differentiation into neurons and/or glia
Marginal zone = decreased cell bodies; contains axons that will eventually be myelinated (white matter — more superficial)
There are five total closure sites involved in formation of the neural tube.
Failure of site 1 results in what condition?
Spina bifida cystica
There are five total closure sites involved in formation of the neural tube.
Failure of site 2 results in what condition?
Meroencephaly (anencephaly)
There are five total closure sites involved in formation of the neural tube.
Failure of sites 1,2, and 4 results in what condition?
Craniorachischisis
There are five total closure sites involved in formation of the neural tube.
Nonfusion of which site is most rare?
Site 3
Differences between spina bifida occulta, w/ meningocele, w/ meningomyelocele, and w/ myeloschisis
SB Occulta = unfused neural arch, skin remains intact
SB w/meningocele = meninges extrude
SB w/meningomyelocele = meninges and neural tissue extends
SB w/myeloschisis = open neural tissue
Glioblasts differentiate from neuroepithelial cells. After neuronal formation ceases, they become _____ and ________
Astrocytes; oligodendrocytes
Once glial prodution stops, cells differentiate into _____ cells.
Microglia are not derived from neuroepithelium like the neuroblasts and glioblasts, but instead are derived from _______
Ependymal
Mesenchyme
_____ controls the proliferation and patterning of neuroepithelial cells via _____ transcription factors
SHH; GLI
Differentiation of SC produces thick walls but thin roof and floor plates
This produces a shallow, longitudinal groove on each side called the ____ _____
Sulcus limitans
The sulcus limitans separates what structures?
Alar plate (dorsal) Basal plate (ventral)
What forms from cell bodies of alar plates?
Dorsal gray columns (afferent nuclei)
Dorsal gray horns
Dorsal median septum also forms with enlargement of alar plates
What forms from cell bodies in basal plates?
Ventral and and lateral gray columns
Ventral and lateral gray columns that form from the basal plates then go on to form efferent nuclei. The ventral gray horns are _______ while the lateral gray horns are ________ (in terms of function)
Axons will also grow out to form the ventral roots of ____ ___
Somatic
Autonomic
Spinal nerves
As the basal plates enlarge, they bulge ventrally on each side to form what?
Ventral median septum
[a deep longitudinal groove (ventral median fissure) develops on the ventral surface]
Basal and alar cranial nerve nuclei are organized into what 7 columns?
[roof plate]
- Somatic efferents
- Branchial efferents
- Visceral efferents
- Visceral afferents
- Special visceral afferents
- General afferents
- Special somatic afferents
[floor plate]
The brain develops during the 3rd week from the neural tube, cranial to the 4th pair of somites.
Fusion of neural folds in cranial region and closure of rostral neuropore form the ____ ____ ____
Primary brain vesicles
What are the 3 primary brain vesicles?
Forebrain = prosencephalon
Midbrain = mesencephalon
Hindprain = rhombencephalon
During the 5th week, secondary brain vesicles form. the forebrain (prosencephalon) divides to form the _____ and _____.
The midbrain does not divide - so remains the mesencephalon.
The hindbrain (rhombencephalon) divides to form the ____ and ____.
Telencephalon; diencephalon
Metencephalon; myelencephalon
During the 5th week, the embryonic brain grows rapidly and bends ventrally with the head fold.
Bending produces the ______ flexure and _____ flexure.
Unequal growth produces the _______ flexure in the opposite direction, which is the metencephalon-myelencephalon junction.
Midbrain; cervical
Pontine
[brain flexures produce considerable variation in position of gray and white matter
The cervical flexure demarcates the ____ from the _____
The junction is arbitrarily defined as the level of superior rootlet of C1 (roughly located at foramen magnum)
Hindbrain; SC