Neural Development (Quiz 4) Flashcards
Human development is divisible into 2 primary periods. What are they?
1) pre-natal (before birth)
2) postnatal (after birth)
Development of the NS begins in the embryonic period (at the time of fertilization when the union of a spermatozoon and an oocyte form a zygote) and extends into the….
post-natal period
A zygote is unicellular with 2 sets of chromosomes- paternal 46 ___ and maternal 46 ____
XX, XY
By 36 hours, the zygote divides into 2 cells, then has rounds of cleavage divisions forming an embryo- ______ then blastocyst over 6 days
morula
What are blastomeres?
identical cells
What are blastocysts?
its the cell/embryo that implants into uterus
Secondary oocytes have not completed meiosis 2 due to a protective mechanism. The secondary oocyte will only complete meiosis 2 when it penetrates sperm. Where was sperm made?
seminiferous tubules of the testes
define morula
solid ball of cells
define blastocyst
hollow ball of cells with an inner cell mass that becomes embryo and everything else becomes extra-embryonic tissue
there is a blastocele cavity and trophoblast cells (outer layer)
ICM becomes….
bilaminar disc
What does gastrulation start with?
primitive streak
What does gastrulation end with?
trilaminar disc
What are the primary germ layers and when were they formed?
formed during gastrulation
-endoderm
-mesoderm
-ectoderm
What is the internal germ layer?
endoderm
What does endoderm form?
lining of gut and other internal organs (basically anything visceral)
What is the external germ layer?
ectoderm
What does ectoderm form?
-skin
-brain
-NS
What does the mesoderm form?
-muscle
-skeletal system
-circulatory system
The NS begins to form in the 3rd week of development. The first evidence of the developing NS is a thickening of the ectoderm of the trilaminar embryo, the _____________. Its a thickening of a longitudinal band of ectoderm in response to chemicals from the underlying midline mesoderm
neural plate
The neural plate begins to fold medially forming a….
neural groove
Either side of the neural groove are the _______________. As the neural groove deepens, the folds start to fuse, the initial join is at the location of the future cervical spinal cord
neural folds
Put structures in order from 1st to appear to last:
-neural tube
-neural groove
-neural fold
-neural plate
-cranial neuropore
-caudal neuropore
1) neural plate
2) neural groove
3) neural fold
4) neural tube
5) cranial neuropore
6) caudal neuropore
Which structure is this?
-thickening of ectoderm between primitive node and oropharyngeal membrane
neural plate
Which structure is this?
-neural folds join in the midline to form this structure and fusion of the folds proceeds cranially and caudally, eventually leaving a cranial and caudal neuropore (open ends)
-it separates from surface ectoderm to lie between it and the notochord
-the cranial part forms the brain and the caudal portion forms the spinal cord
-the lumen forms the central canal of spinal cord and ventricular system of the brain
neural tube
Which structure forms the lamina terminalis?
cranial neuropore (its also the first structure to close!)
Neurulation is the process of formation of the hollow neural tube by folding the epithelial neural plate. Neurulation in humans occurs in 2 distinct phases. What are they?
1) primary neurulation during weeks 3/4 of gestation leading to the development of the brain and spinal cord
2) secondary neurulation during weeks 5/6, with formation of the lower sacral and coccygeal cord with the help of the neural crest cells
defects of either of these can lead to abnormalities and usually miscarriages
Fusion of the neural folds forms the….
neural tube
Fusion proceeds cranially and caudally. By the end of the 4th week the tube is closed, a process called __________________. The close neural tube pulls away from the overlying ectoderm. A cluster of cells forms from the crest of each neural fold and fills the gap between the neural tube and ectoderm. This is the __________.
primary neurulation, neural crest
Neural crest cells will develop into the….
PNS
The formed neural tube develops into the..
CNS
The neural tube hole in the middle will form the….
ventricular system and the central canal of the spinal cord
What is A?
neural crest
What is B?
neural tube
What is C?
ectoderm
What is D?
mesoderm
What is E?
notochord
The notochord releases ______
transcription factors
The pattern of development and differentiation among the cells of the neural tube becomes visible during the 4th week when a long groove forms in the lateral wall. This is the _____________. It defines dorsal and ventral
sulcus limitans
The gray matter dorsally forms the…
alar plate
The gray matter ventrally forms the…
basal plate
As the neural tube is closing (cranial and caudal) a bulge begins to form at the rostral end, this will form the future brain. At the end of the 4th week, 3 bulges can be seen along the tube. The bulges are referred to as primary vesicles. What are the 3 primary vesicles from cranial to caudal?
1) proencephalon
2) mesencephalon
3) rhombencephalon
The primary vesicles are not along a straight line, flexures bend the tube. What are the 2 flexures?
test q
1) cranial flexure (between rhombencephalon and future spinal cord)
2) cephalic or mesencephalic flexure (at the level of the midbrain)
Where is the cervical flexure located?
test q
between the rhombencephalon and future spinal cord
Where is the cephalic or mesencephalic flexure?
test q
at the level of the midbrain
The 3 primary vesicles form 5 secondary vesicles. What are they?
**need to know them in order!!!
1) telencephalon
2) diencephalon
3) mesencephalon
4) metencephalon
5) myelencephalon
The prosencephalon gives rise to the…
telencephalon and diencephalon
The telencephalon becomes the….
cerebral hemispheres
The diencephalon becomes the….
-thalamus
-hypothalamus
-neural retina
The mesencephalon remains one vesicle undivided and develops into the…
midbrain
The rhombencephalon forms the…
metencephalon and myelencephalon
The metencephalon becomes the…
pons and cerebellum
The myelencephalon becomes the…
medulla oblongata
Where does the pons start to form?
at the pontine flexure
Where does pontine flexure form?
between the metencephalon and myelencephalon
As the pontine flexure develops, the neural tube laterally widens and flattens forming a diamond shaped cavity called __________________. A thin membrane covers the top forming the 4th ventricle. The alar and basal plates are now the floor of the 4th ventricle. The alar plate is sensory and lateral while the basal plates are motor and medial
rhombencephalon
What is the essential landmark for dorsal vs ventral?
sulcus limitans
The telencephalon grows and expands much quicker than other areas. 2 large swellings form connected at the midline by a ___________________. This will be the future location for the corpus callosum which is a massive bundle of commissural fibers connecting the 2 hemispheres
lamina terminalis
The basal region of the forming telencephalon thickens and forms the primordia of the future….
basal nuclei (gray matter)
The telencephalon folds along the lateral sides of the developing diencephalon, this area overlying the future thalamus forms the ___________. The forming cortex adjoining this structure expands covering it
insula
As the telencephalon is forming and expanding, the diencephalon is thickening and moving ________
medially
The thalamus and hypothalamus form separated by the ________________________
hypothalamic sulcus
As the rostral neuropore closes, a diverticulum the optic vesicle appears, everything caudal to the optic vesicle is diencephalon. The optic vesicle will become ______________. The cavity of the diencephalon forms the __________________
future retina, 3rd ventricle
The caudal end of the neural tube, which is after the 4th pair of somites, develops to form the ______________. Cells on the dorsal side form the alar plate, which subsequently becomes the dorsal horn. Cells at the ventral end form the basal plate, which then becomes the ventral horn
spinal cord
What is the last part of the neural tube to close?
caudal neuropore
What happens if the neural tube doesn’t close properly/fully?
spina bifida
most commonly occurs in caudal end and lumbar region
Early development of the spinal cord is influenced by the maternal dietary requirement for ________ for closure of the neural tube
folate
The neural tube gets thicker and the neural canal becomes thin, forming the….
central canal
The epithelial cells forming the neural tube differentiate into ____________ which give rise to neurons and glia. Astroblasts and oligodendroblasts are formed
neuroblast
Later development of the spinal cord requires the contribution of neural crest associating with the cord to form the….
DRG and ventral sympathetic ganglia
The _________ roots become myelinated before the ________ roots
motor, sensory
What will the neural crest form?
test q- know at least 2 of them
-entire PNS
-sensory of autonomic ganglia
-schwann cells (myelinates axons in PNS)
-adrenal medulla
-cutaneous pigment cells
they may also move into the head and form:
-bones of the skull
-smooth muscle of pharyngeal arches
-lens of eyes
-anterior pituitary gland
-ganglia of CN V, VII, IX, and X (afferent)
Where does neurulation start in embryo?
in the center
___________ has 2 main embryo regions. The head is at CNS level and differentiates slightly earlier at the mesencephalic region of neural folds. The body is at the spinal cord level at the lateral edges of the fused neural tube
Neural crest
Cranial placodes are specialized regions of the ectoderm, which give rise to the various sensory ganglia and contribute to the pituitary gland and sensory organs of the vertebrate head. Basically cranial placodes is ectoderm with….
neural crest
The olfactory placodes will become….
olfactory epithelium
The DRG, autonomic ganglia, and the adrenal medulla originate from the cells of the….
neural crest
T/F: transcription factors help make neural crest cells
true
