Neuro I Flashcards
duplication at 2 cell blastocyst stage
2 separate sets of fetal membranes
duplication of inner cell mass
free twins of two separate embryonic discs; asymmetrical if unequal separation;
shared fetal yolk sac and chorion
gastrula: complete duplication of primitive streak
conjoined (tissues/organs)
symmetrical (2 complete, separate axes)
2 heads and vertebral columns
gastrula: incomplete duplication of primitive streak
conjoined, symmetrical; duplicated region 2 axes
unduplicated region; 1 axis;
at gastrula, all fetal membranes shared
duplication of gastrula without duplication of primitive streak
conjoined, asymmetrical
1 axes
other body tissues/ parts duplicated
especially limbs
what is the notochord
mesodermal rod;
notochord begins at
primitive node - deep to it and ectoderm
notochord oriented
craniocaudal along midline of longitudinal axis of embryo
notochord expands
cranial and caudal
as the notochord expands caudally, primitive streak ____
disappears
paraxial mesoderm
next to axis; mesodermal columns or bands, located on either side of notochord
what forms the paraxial mesoderm
somites from left and right pairs
somites form _____
sequentially from cranial to caudal
which forms first
cranial most pair
somites give rise to
segmental skeletal/connective tissue structures and muscle units (pattern imposed on developing peripheral nervous system)
first several fuse and contribute to
head structures
canine somites caudal to head include
8 cervical 13 thoracic 7 lumbar 3 sacral 10-20 caudal
notochord and paraxial mesoderm together begin
NS development
overlying ectoderm induce
neurectoderm (ectoderm above the notochord)
rest of ectoderm (surface ectoderm)
becomes epidermis
neuroectoderm gives rise to
neural plate
neuronal progenitors
neurons
glial progenitors
astrocytes, oligodendrocytes, etc (excludes microglia)
ependymal cells
line tubes and ventricles
formation of primary neural tube is the formation of
brain and majority of psinal cord and associated nerves
primary neural tube develops from
neural plate
neural plate is
proliferation and thickening of neuroectoderm
majority of the neural plate is
CNS
neural crest cells at edge of neural plate
PNS
Neural folds do what
elevate and grow toward each other at lateral edges
center of neural plate does what
sinks along long axis of body to from neural groove
neural crest cells are found at the junction of
neuroectoderm and surface ectoderm
as neural folds continue to grow toward one another, what happens to the neural groove
deepens
neural folds fuse to become
neural tube
neural tube created is a complete circle of
complete circle of neuroepithelium surrounding a neural canal
neural cres cells isolate from
neuroepithelium of neural tube and surface ectoderm, located between them on either side of the axis
surface ectoderm meets and fuses above
neural structures
fusion begins in the center and extends
outward along body axis in both directions (cranially and caudally)
chicks develop from
a single intitial fusion point while mammals tend to have multiple initial fusion points
openings at rostral and caudal ends are
rostral neuropore and caudal neuropore
primary neurulation is complete when
rostral and caudal neuropores are closed
secondary neurulation begins after
closure of caudal neuropore and completion of primary neurulation
located at about the _____ pair of somites
35th
secondary neural tube arises from
neuroectodermal cells of the tail bud or caudal eminence
proliferation and condensation of cells
x
caviation
forming a central cavity or lumen
fuses with caudal end of
primary neural tube
lumen becomes conitnuous with
neural canal
neural canal
ventricular system
