Development of the nervous system Flashcards
Lecture 3
growth
an increase in the number of cells and enlargement of cells
morphogenesis
development of a unique structure (differentiation, proliferation, apoptosis)
propagation/proliferation
increase in number of the same cell type
differentiation
development of a new (different) cell type
apoptosis
programmed cell death
week 1 stages
1) fertilization (zygote)
2) cleavage (morula)
3) blastocyst formation (blastocyst)
- epiblast becomes embryo
- hypoblast becomes yolk sac which becomes chorion
4) implantation
week 3 - gastrulation
formation of 3 layers as some epiblast cells proliferate and migrate through the primitive streak (PS)
- endoderm
- mesoderm
- ectoderm
endoderm
PS epiblast displace the hypoblast cells
mesoderm
PS epiblast become mesenchyme (migrating cells) which become mesoblasts
ectoderm
remainder of the epiblast cells
totipotent cells
can form any cell of the body, only cells undergoing cleavage
pluripotent cells
can form any cell of the body except for the placenta
notochord
arises from movement of PS cells cranially, defines primordial axis of embryo, basis for axial skeleton development, induces the nervous system to develop
neurulation
1) notochord induces thickening of neural plate (previously ectoderm)
2) invagination of neural plate forms neural groove, which has neural folds one ach side
3) neural folds fuse together, forming the neural tube
4) neural crest cells fuse, as do surface ectoderm cells
5) neural crest cells migrate away from neural tube
somites
arise from segmentation of the paraxial mesoderm, differentiate into:
- sclerotomes: give rise to vertebreae
- myotomes: gives rise to skeletal muscle of trunk and limbs
- dermatomes: give rise to dermal skin component
neural tube structures
neural tube seals, anterior (rostral) and posterior (caudal) neuropores seal last
- rostral = brain
- cavity = ventricular system
- caudal = spinal cord
neural crest cells
forms the basis of the cells of the PNS