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what are the 3 main things it makes and examples of each?
surface ectoderm, epidermis - skin, nails, hair, mouth epithelium, lens, cornea
neural crest- PNS, adrenal medulla, melanocytes, face cartilage, dentine of teeth
neural tube - brain, neural pituitary, spinal cord, motor neurons, retina
how does the neural tube stick to itself and not to the other ectoderm?
initially they all express E cadherin, but neural plate starts upregulating N cadherin and NCAM so it connects to itself but less to the other ectoderm
how do the neural crest cells leave?
they stop expressing E cadherin
how does complete closing occur in the neural tube?
- starts in the anterior then zips up to the posterior
- 2 holes are still at each end called A/P neuropores
what are the 2 diseases you can get if you dont close the neuropores?
Anencephal – don’t close the anterior part of neural tube (forebrain) then the neurons in forebrain structures get exposed to amniotic fluid so they die (complete death)
Spina bifida - Posterior end of nerve tube – depends on degree of damage, the spinal cord is exposed to amniotic fluid, loss of neurons
how can folic acid supplementation lower risk of NTD (neural tube defects)?
Folic Acid – folate binding protein (receptor for folic acid) expressed on dorsal most region of tube prior to fusion (expressed right along those folds right before fusion)
lots of times women dont know they are pregnant though and neural tube closing happens early (at day 22)
what are the 3 primary vesicles?
- forebrain (prosencephalon)
- midbrain (mesencephalon)
- hindbrain (rhombencephalon)
what are the 5 secondary vesicles?
what does the telencephalon make?
- olfactory (smell)
- hippocampus (memory)
- cerebrum (association - intelligence)
diencephalon makes what?
- optic vesicle (vision)
- epithalamus (pineal gland)
- thalamus (relay center for optic and auditory neurons)
- hypothalamus (temp, sleep, and body regulation)
midbrain (fiber tracts between anterior and posterior brain, optic lobs, and tectum)
- cerebellum (coordination of complex muscular movements)
- pons (fiber tracts between cerebrum and cerebellum, mammals only)
medulla (reflex center of involuntary activities)
how does the future brain region expand?
occlusion in the neural tube, positive pressure increases and the cavity swells
how are compartments set up in the forebrain?
- same as rombomeres genes but called prosomeres
- also homeodomains
- Otx is an example of a transcription factor
how does Shh function in the D/V axis?
- makes things ventral
- diff amounts turn on diff transcription factors
- diff neurons will form with diff amounts of exposure to Shh (depends on distance to notocord)
whats the name of the original neural tube cells? then whats it called?
- germinal neuroepithelium (one cell layer thick of stem cells)
- ...ventricular zone
how is position of nucleus a function of cell cycle in the ventricular zone?
G1, G2, and M nuclei are close to the lumen of the neural tube
cell cycle goes: G1 - S - G2 - M
how is the cell division oriented in the cells of the ventricular zone?
vertical, otherwise one daughter cell would float up and away
neurons are produced when in pregnancy?
during the first half
how do the neuroblasts travel?
- glial cells have extend their processes all the way through the neural tube
- a neuroblast divides HORIZONTALLY, officially stops dividing, then migrates up the glial (that day is its birthday)
- the earlier the birthday the sooner it gets off the glial highway, later birthdays travel farther
whats a cell called on its birthday?
how are cells of the neocortex in the brain organized?
- into clusters (nuclei)
- and layers (cortices)
clusters of neurons inside CNS? outside CNS?
what phase is it of the cell cycle that determines how far a cell will travel into the cortical layers of the neocortex in the brain?
*experiments transplanting young bday cells into old ventricular tissue and seeing how far the cells travelled
how are whiskers made?
- FGF8- rostral - whiskers
- FGF changes affects I.D. of diff cortical regions
what makes human brain different?
- 1.Retention of fetal growth rate after
- birth (for about 2 years).
- 2.Activity of human specific RNA genes.
- 3.Transcription activity - high
- 4.Human-specific alleles of developmental
- regulatory genes (such as FOXP2 gene)
- 5. Continuation of brain maturation into adulthood
what is Foxp2?
- - key tx factor in human brains that is important for speech and language
- - expressed in other animals but in different locations not the brain
what are the HARs?
- human accelerated regions
- regions of DNA that vary a lot between human and chimp compared to chimp and chicken
- they found 49 (HAR1- HAR49)
- differed the most
- codes for protein that guides cortical neurons early in development, important in making diff layers and connections
- in the cerebral cortex
how can plasticity of human brain be represented?
myelination increases sooo much as you get older (but downside to that is tons of demyelinating diseases)
- also pruning: emotional (amygdala) lights up a lot but then you get pruning (more
are there stem cells in the brain? how did they find this out?
yes! can make glia and neurons! they do not exist with the aim to repair though, maybe just make new connections
inject BrdU, which is expressed in cells that are actively dividing!
where are the brain stem cells?!
olfactory and hippocampus
when does growth of synapses cease?
how do you get curve of cornea?
what differentiates lens from retina?
- lens has otx2 in it
- then pax 6,
- then sox 3
no pax 6 in optic vesicle, but pax 6 in lens then you get:
an eye, but other way around you dont
what is interesting about pax 6?
- very conserved
- photoreceptor organs across phylum
describe epithelial-mesenchymal interaction in making a hair:
dermal fibroblasts (mesenchyme) tells epidermis (epithelia) to aggregate cells in the basal layer (placode) and then sink into the dermis - dermal fibroblasts respond by forming a small node called a dermal papilla - epithelia respond by dividing more rapidly - keratinized hair shaft
what needs to exist in hair in order for it to regenerate?
dermal papilla, stem cells from bulge come down and help
how does the hair get pigmented?
basal cells carry melanocytes with them as they ingress down into the dermis
types of hair:
terminal and vellus
how does hole at top of hair form?
what would a 3rd bulge in an armpit cell be?
apocrine sweat gland - stinky
how is a hair follicle going to form instead of epidermis?
- competition between Wnt and Dickkopf (wnt inhibitors)
- so ultimately is B-catenin there (stabilized?)
B catenin responsible for placode
*think of the Wnt suppressed mouse
describe the stem cell bulge?
they continuously migrate through the outer root sheath and then become any of the 7 hair layers
E/M interactions into the dermis?
and out of the dermis?
in: Hair, Sweat gland, Mammary gland, Tooth
out: feather, limb, scale
what is atavism?
- mutant that expresses something that way back in evo history it used to express (ex: whale with rudimentary
- femur even though it obviously doesn’t have a leg)
how is the talpid chicken a mutant?
- : jaw mesenchyme that’s supposed to make teeth does not come in close contact with the jaw epithelium to make teeth, but in the mutant chicken (talpid) these parts come close enough so that teeth do form
- - epithelia has ability to make teeth but is normally not stimulated to do so