Test 1 Flashcards
(574 cards)
germinal period
2 weeks in length
migration of zygote (fertilized ovum) to uterus:3-4 days
rapid increase in cell number
by day 9-12 the blastocyst embeds itself in the endometrium
3 stages of prenatal motor development
germinal- 0 to 2 weeks
embryonic- 2 to 8 weeks
fetal- 8 to 40 weeks
gastrulation
embryo transforms from bilaminar to trilaminar day 15-16
Neurulation
- process by whereby the neural plate forms the neural tube
- lateral edges of the neural plate become elevated and form the neural folds; depressed mid region becomes the neural groove
- gradually the neural folds approach each other in midline, where they fuse
- closure of cranial and caudal neuropores
closure of cranial neuropore
day 25
closure of caudal neuropore
day 28
neurulation-week 3
- the notocord (dorsal cord) appears at the end of gastrulation
- notocord sends signals that causes cells of the ectoderm just above it to thicken
- neural plate begins to invaginate to form neural groove
- neural groove rises from embryos surface and closes to form neural tube
what defines the rostral- caudal axis
notocord, cylinder of cells, in the mesoderm
extends along entire length
neural crest cells
cells break away from epithelial layer of the developing dorsal neural tube and subsequently migrate as mesenchymal cells
crest cells travel to many areas of the developing embryos and give to rise to
dorsal root ganglion ANS ganglia ganglia to CN V, VII, IX, X schwann cells meninges pigment cells MS components of head
brain development
begins at day 28
superior neuropore closes, neural tube expands to form 3 enlargements (2 subsequent enlargements also appear)
enlargements are hollow
3 main divisions of the brain
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
prosencephalon (forebrain)
telencephalon- cerebral hemisphere
diencephalon- thalamus, hypothalamus, epithalamus
mesencephalon (midbrain)
connects forebrain to hindbrain
rhombencephalon (hindbrain)
pons, medulla, cerebellum
spinal cord develops from
caudal end of neural tube. continuous with rhombencephalon
organization of gray/white matter
white matter: marginal zone
grey matter: dorsal cell bodies from alar plates. ventral cell bodies/ lateral grey columns from basal plates
when does myelination occur
throughout the first year of life
somites
cells formed in segmental pairs along the neural tube from mesoderm layer
give rise to vertebrae, muscles of back and body wall, and dermis of skin
development of somite
paraxial mesoderm cells (from neural crest) undergo further differentiation to develop into segment series of tissue blocks (somitomeres/somites) on either side of the neural tube
somites develop into 2 things
1) myotome- cells in dorsolateral regions from muscle cells; migrate beneath dorsal epithelium (dermatome)
2) sclerotome: cells in ventromedial wall lose epithelial arrangement; become mesenchymal
embryonic CT
1) fibroblasts
2) chondroblasts
3) osteoblasts
each somite gives rise to and differentiates into 3 things
- ventromedial sclerotome (vertebrae and ribs)
- myotome (muscles)
- dermatome (skin)
where do the first pair of somites develop
a short distance posterior to cranial end of the notochord. the rest form caudally