embryology Flashcards
what are the two reasons for nervous system organization?
functional and developmental
characteristics specific to vertebrates
- bilaterally symmetrical
- have a head and tail
- bodies are segmented
- hollow, dorsal neural tube
vertebrates at bilaterally symmetrical
- structures are situated so that they are paired and a mirrored image exists on the opposite side
- this is a developmental characteristic that is seen in some intervertebrates as well
all vertebrates have a head and tail
- a zygote is polarized very early on and all systems are set up to reflect this
- alimentary canal starts at the head and ends at the tail
- the senses are all clustered around the start of the digestive canal near where we take in food
- consequently, we get a “swelling” at the front or beginning because we need to deal with all the stimuli there
all vertebrates bodies are segmented
- the body is constructed of repetition of segments
- these are situated perpendicular along a long axis
- each segment developmentally produces accompanying organs and systems
all vertebrates have a hollow, dorsal neural tube
intervertebrates have a solid rope-like nervous cord
mitosis starts within ____________
24 hours
in 3-4 days a sphere of cells called the ________ is formed
morula
- morula becomes hollow sphere of cells called blastocyst
- enters uterine cavity and implants in all at about 6 day post fertilization
week 1
one part of hollow ball starts to fold inward, creating 2 layers or bilaminar embryo
week 2
- becoms trilaminar (3 layers called germ layers)
- once layers start to form, called a gastrula
week 3
inducing power
notochord
neural plate is seen _________
18-19 day PC
cell proliferation produces an _____
inward folding
inward folding starts ______
21-22 days PC
when the inward folding seals it creates the _____
neural cord
inward folding sealing happens ____
22-26 days PC
what do the growths on both sides of the neural tube become?
neural crest
the neural crest eventually becomes the ____
PNS
the spot on the neural tube where the closure begins eventually becomes the _____
midbrain
anterior end of neural tube
anterior neuropore
what happens if the anterior neuropore does not close correctly?
the brain wont develop
closure of the anterior neuropore happens ________
24-25 days PC
anterior end closes ____ than the opposite end
sooner
after closure of the anterior neuropore a bulge of cells form, this bulge eventually becomes the
brain
the end opposite to the anterior neuropore is the
posterior neuropore
if the posterior neuropore doesn’t close correctly
spina bifida
closure of the posterior neuropore happens __________
around day 26 PC
what do the bulges eventually grow and create?
when does this happen?
they create the three vesicle system (primary vesicles)
happens by the end of week 4
what are the names of the three vesicles?
- prosencephalon
- mesencephalon
- rhombencephalon
what do the three vesicles develop into?
the brain
when do the three vesicles turn into five vesicles?
week 5
- forebrain
- grows fastest
- eventually separates into the telencephalon and diencephalon
prosencephalon
the midbrain
mesencephalon
- hindbrain
- develops into two lobes
rhombencephalon
develops into cerebellum and pons
metencephalon
develops into medulla
myelencephalon
when the two hemispheres of the telencephalon start to pinch what is that the starting formation of?
the corpus callosum
- inside remains hollow but begins to fill with CSF
neural tube
develop into
- most of PNS
- sensory receptors in muscles
- pigment in skin cells and iris
- adrenal medulla
neural crest cells
- where epinephrine is produced
- on top of kidneys
adrenal medulla
a peptide which causes cell proliferation and development
NGF
- area closest to the ventricle
- where cells divide
- cells are forced outward after genesis forming concentric rings
germinal zone
- second connection rings
- cells differentiate in morphology
- gray matter forms
mantle
- outer most layer
- myelin produced
- produces glial cells
marginal
the elongation of circles form the medial horizontal crease called the
sulcus limitans of his
- dorsal portion
- sensory afferent portion of spinal cord
- contains neurons that carry info from PNS to brain
alar
- ventral portion
- motor efferent
- motor neurons from spinal cord to muscles
basal
majority of the brain comes from the ______
alar
what are the development of head and face induced by
neural crest cells
what is thickening called
placodes
- occur in the head
- each needs neural crest
- own set of rules
- sends sensory receptors directly to brain
- only vertebrates have them
placodes
