Term
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Definition
| name for the entire head skeleton |
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Term
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Definition
| the skull without the mandible |
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Term
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Definition
| the skull minus the facial skelton |
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Term
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Definition
| the neurocranium and basicranium enclose the |
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Term
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Definition
| covers the brain from above, front, and back on both sides, also supports the brain from beneath a little(in front and back) |
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Term
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Definition
| part of the skull that mainly supports the brain from beneath |
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Term
| intramembranous ossification |
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Definition
| how does the bone of the neurocranium form? |
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Term
| endochondral ossification |
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Definition
| how does the bone of the basicranium form? |
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Term
| mesoderm (and a small bit of neural crest) |
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Definition
| what embryonic tissue makes up the basicranium? |
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Term
| a mixture of mesoderm and neural crest cells |
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Definition
| what embryonic tissue makes up the neurocranium? |
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Term
| viscerocranium, splanchnocranium |
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Definition
| what are the 2 other names for the facial skeleton |
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Term
| intramembranous ossification |
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Definition
| how do the bones of the face form? |
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Term
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Definition
| what embryonic tissue makes up the face? |
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Term
| the capsule -> both mesoderm and neural crest cells (there is a potential space between the brain and capsule) |
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Definition
| as the brain is developing, what is the first skull precursor structure that forms around the developing brain? what embryonic tissue forms this structure? |
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Term
2 layers: endomeninx, and ectomeninx
(there is a potential space between the 2 layers) |
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Definition
| what does the capsule (skull pre-cursor) differentiate into? |
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Term
endo is closer to the brain, so neural crest cells
ectomeninx becomes the skull which forms from both mesoderm and neural crest cells |
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Definition
| what embryonic tissues make up the endomeninx? the ectomeninx? |
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Term
| each divides into 2 layers |
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Definition
| what is the next step of development after the ecto/endo meninx form? |
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Term
the internal layer contacts the brain -> pia mater
the outer layer of endomeninx -> arachnoid mater
both neural crest |
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Definition
| what do the 2 layers of the endomeninx form? |
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Term
the inner layer becomes the dura mater, made mostly of mesoderm (with a little neural crest maybe)
the outer layer is both neural crest and mesoderm and becomes the bones of the membranous neurocranium |
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Definition
| what do the 2 layers of the ectomeninx form? |
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Term
| multiple because it does intramembranous ossification, and there are multiple bones |
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Definition
| how many ossification centers does the neurocranium have? |
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Term
| the tissue starts as the generalized embryonic precursor "loose mesenchyme" -the identical stellate shaped cells separated by a lot of ECM |
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Definition
| what is the starting (embryonic)material for intramembranous ossification? |
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Term
| it becomes condensed mesenchyme as it organizes into layers and elongates into sheets, the extra-cellular spaces are reduced |
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Definition
| what happens in intramembranouse ossification to the loose mesenchyme (what does it do?) |
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Term
| membrane formation -> the extracellular spaces are filled with collagen |
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Definition
| what is the 3rd step in intramembranous ossification? |
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Term
| islands of mesenchymal cells become osteoprogenitor cells which turn into osteoblasts(secrete osteoid which mineralizes) and osteoclasts |
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Definition
| after the extracelluar space begins to fill with collagen, what happens in intramembranous ossification to the cells? |
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Term
| osteoblasts at the periphery expand the bone |
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Definition
| how does the bone grow once the osteoprogenitor cells are trapped in the centers of the bony islands(now called osteocytes) in intramembranouse ossification? |
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Term
| it is spongy, and makes spicules that radiate from the center outward (these rays are visible in fetal skulls that are not fully ossified) |
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Definition
| what is the newly formed bone at the ossification center of intramembranous ossification like? |
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Term
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Definition
| a strip of CT that keeps bones from separate ossification centers from growing together |
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Term
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Definition
| a craniofacial articulation in which contiguous margins of bone approximate each other and are united by a thin layer of fibrous tissue |
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Term
| not entirely, they allow molding of the skull, or deformation of the neurcranium to facillitate birth |
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Definition
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Term
1) allow modling of skull for birth
2) allow pre-natal and post-natal bone growth |
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Definition
| name 2 the functions of sutures |
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Term
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Definition
| ______ molding during bith keeps bones from fracturing, but can cause the baby to have a cone head temporarily |
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Term
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Definition
| as neurocranial bones expand these are the site of new bown formation |
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Term
| sutures widths are maintained |
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Definition
| the rate of bone formation at the argins keeps pace with the expanding brain, what does this mean? |
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Term
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Definition
| why must sutures remain narrow? |
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Term
remodeling:
there must be DEPOSITION on the OUTER surfaces and
RESORPTION of the bones INNER surfaces to flatten the bones and conform to the brians contours
there is more resorption/deposition on the margins of the bone than the centers |
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Definition
| its not enough to add new bone at the margins for the skull to grow, something else must be done to fix the curvature of neurocranial bones, what? |
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Term
1) loose mesenchyme makes a model
2) becomes dense mesenchyme
3) chrondrocytes form a hyaline cartilage model
4) cartilage model is replaced by bone
*this is used for long bones and the basicranium |
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Definition
| describe the steps in endochrndral ossification |
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Term
| one at the center(diaphysis) then the ossification spreads bidirectionallr to the ends toward the epiphysis |
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Definition
| how many centers of ossificaiton are in endochondral ossification? |
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Term
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Definition
| regions of the chondrocranium that do not ossify initially and persist as cartilaginous zones between bones(analogous to growth plates in long bones) |
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Term
between the sphenoid and the occipital bone(basilar part)
aka the sphenobasilar synchondrosis |
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Definition
| what is the most important/primary site of postnatal growth in the cranial base? |
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Term
the first is the frontalethmoidsphenoid (FES) at age 6-7
they proceed to close anterioposterior until the final one the sphenobasilar/basoccipital closes age 19-21 |
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Definition
| which of the synchondroses in the skull fuse first? last? |
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Term
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Definition
| what is the primary direction of growth for the cranial base with age? |
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Term
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Definition
| the primary site of postnatal growth in the cranial base |
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Term
when the genes are on they inhibit bone growth(to prevent ossification of the synchondrosis)
when turned off(from front to back), the synchodroses fuse and close so there is no more growth |
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Definition
| what do the hedgehog genes (sonic/indian/desert) do to the synchondroses? |
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Term
| it grows in the middle where the hyaline cartilage is and pushes the bone out on both sides |
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Definition
| on what side of the synchondrosis does the growth occur? |
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Term
1) resting zone (normal hyaline cartilage)
2) proilferative zone (chondrocytes divide and stack up, pushing the bone)
3) hypertrophic zone (chondrocytes swell and the ECM is reduced)
4) zone of degeneration (chondrocytes die & remaining matrix begins to calcify)
5) ossificaiton zone ( osteoprogenitor cells and capillaries move into the spaces left by the dead chondrocytes, then diferentiate into osteoblasts which begin to form bone |
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Definition
| name the zones going out from the hyaline carilage in a syncondrosis! |
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Term
| they thought that the bones are under strict genetic control, and the cells have intrinsic info about what they should look like (not a lot of evidence of this) |
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Definition
| what was the theory on skull development in the 40s-60s? |
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Term
1950s-70s, it says that:
- skull bones have no intrinsic genetic info
- bne is a passive material that conforms to the shape/size of surrounding structures
- the direct genetic control is in the tissue bone forms around, so bone form is determined epigenetically (by crap around it) |
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Definition
| when did functional matrix theory come about? what is it? |
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Term
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Definition
| the neurocranium forms around the shape of the brain represents what theory in brain development? |
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Term
| microcephaly, supports functional matrix theory -> no excess space in the endocranial cavity, only large enough to cover the brain. |
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Definition
| this nervous system defect causes the brain to be undersized and thus the skull to be undersized as well. Name the disorder and they theory it supports |
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Term
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Definition
| med term from too small eyeball |
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Term
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Definition
| med term for congenitally absent eyeball |
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Term
| it is also too small, supporting functional matrix theory |
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Definition
| if the eyeball is too small, or not present, what happens to the orbit? |
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Term
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Definition
| results form an abnormal accumulation of cerebrospinous fluid within or around the brain |
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Term
| it increases in response so that the brain remains covered and protected, but the sutures are wide because it can't quite keep up |
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Definition
| when the volume of endocranial contents increase, what happens to the growth of the neurocranial bone? |
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Term
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Definition
| how can hydrocephaly be diagnosed prenatally? |
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Term
| they are also absent -anencephaly |
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Definition
| neural defect causing absence of the brain due to the anterior neuropore not closing. what happens to the skull and meninges? name the disorder |
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Term
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Definition
| possibly due to a interruption in arterial blood supply to the brain, the cerebrum is nearly absent in this disorder. |
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Term
it might form normally and give a normal looking baby, the space filling with CSF
this means that the meninges are probably important for determining skull form |
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Definition
| if there is hydrancephaly after the meninges differentiated, what happens to the neurocranium? what does this mean? |
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Term
| bone remodels in response to external physical forces |
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Definition
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Term
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Definition
| application of normal forces on bone (such as from muscle) are necessary for the skeleton to maintain proper form. Also the physical presence of other tissue (teeth in their sockets) maintains the socket. Application of abnormal forces causes bone to resorb. What law is this? |
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Term
| orthodontia & helmets to treat neurocranial deformations |
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Definition
| deliberately chanign the shape of bone by applying controlled forces to it is the basis of what? |
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Term
their mandible (and other bones) do not form properly without muscle pulling them
(a nerve lesion/muscle removal acts similarly) |
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Definition
| what happens in mice if they have a muscular dysgenesis mutation disrupting muscle development? |
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Term
| it fills in, no more tissue blocking it, so the bone remodels |
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Definition
| when teeth are lost what happens to the tooth socket? |
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Term
| the transplantation studies with avian/amphibian embryos, also IHC with mammals |
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Definition
| what evidence supports the idea that there is intrinsic genetic control of bone development? |
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Term
| Bombinator the toad and Triturus the newt |
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Definition
| name the animals important to the hertotopic transplant studies performed in the 40's(1959?) that support the strict genetic control theory |
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Term
| heterotopic transplant studies |
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Definition
| this type of study puts tissue from a donor embryo of one species into the corresponding position of a host. the host embryo is premitted to grow and develop further to see what happens in the transplanted tissue |
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Term
| it was more toad-like than newt-like, but there is clearly BOTH enviromental and genetic factors determining facial bone development contained in the neural crest cells |
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Definition
| what happened to the toad jaw on the newt and what did it show? |
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Term
1) paraxial mesoderm
2) cephalic neural crest |
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Definition
| name the 2 sources of skull bones (embryonic tissue) |
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Term
1) somitomeres from prechordal mesoderm (7 pairs)
2) occipital somites (4 pairs) |
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Definition
| the head muscles come frome 2 sources of paraxial mesoderm, name them |
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Term
| muscle and bone, initially only comes from occipital somites and other paraxial condensations (Somitomeres) |
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Definition
| what does paraxial mesoderm become in the head? where is it from initially? |
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Term
| somitomeres (7 pairs) becomes a lot of the head musculature (muscle and dermis only, no bone) |
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Definition
| partially segmented prechordal mesoderm that forms most of the head (like somites but still connected) |
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Term
| bone, skeletal muscle, dermis (like normal somites) |
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Definition
| occipital somites are cranial to the cervical somites, what do they give rise to? |
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Term
| somites, not mesoderm (direct quote from T Cole 26 min after the break in the 1st lecture) |
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Definition
| mesoderm derived bone in the head comes only from where? |
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Term
either side,
comes from ectoderm of both types (neurectoderm and surface ectoderm) |
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Definition
| where are neural crest cells found in relation to the neural tube? what tissue does it come from? |
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Term
| pluripotent, does a lot of tissue types, but not all |
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Definition
| are neural crest cells omnipotent, pluripotent, or totipotent? |
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Term
| they act like mesoderm and become cartilage and bone (indistinguishable physiologically and histologically) |
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Definition
| what is special about cephalic neural crest cells? |
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Term
| once they have migrated to their destination, they are undifferentiated at the point of origin |
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Definition
| when do neural crest cells differentiate? |
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Term
| It starts in the CNS with the segmentation of the BRAIN, this drives other structures to segment, and establishes the paths of neural crest migration |
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Definition
| where does segementation of the embryo start? why is this important? |
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Term
| forebrain, midbrain, hindbrain |
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Definition
| name the first 3 parts of the brain that segment |
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Term
1) telencephalon
2) diencephalon
3) mesencephalon
4) metencephalon
5) myelencephalon |
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Definition
| name the parts of the brain when it forms 5 segments |
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Term
| 4 protorhombomeres segment into 7 rhombomeres |
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Definition
| the hindbrain first segments into 4 ______ 's then these divide into 7 _______ |
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Term
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Definition
| what brain segment gives rise to the brainstem? |
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Term
| HOX genes, except the first rhombomere (R1) |
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Definition
| how does the hindbrain know to make rhombomeres? |
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Term
| no, they are expressed in waves of different combinations which correspond to the formation of different rhombomeres, or vertebrae etc (which then go to influence other stuff) |
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Definition
| do hox genes have continuos actions? |
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Term
1) posterior midbrain + R1 + R2
2) R4
3) R6
4) R7 |
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Definition
| where does neural crest streams come from(specifically) to form the first 4 branchial arches? |
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Term
| not in humans, it dissapears |
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Definition
| is there a 5th branchial arch? |
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Term
| R3, R5 they contain the inhibitory Bmp4 gene |
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Definition
| which rhombomeres do not give rise to neural crest cells? what do they do? |
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Term
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Definition
| a bone morphogenetic protein helps to keep the streams of migrating neural crest cells separate, by inhibiting nueral crest cells from leaving specific rhombomeres; name it |
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Term
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Definition
| neural crest cells migrate in ___ not sheets |
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Term
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Definition
| somitomeres of paraxial mesoderm alongside the brain is also segmented, and patterned so that ___ can innervate them |
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Term
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Definition
| what gives rise to the mesoderm in the basicranium and neuocranium? |
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Term
| if you transplant tissue from the japanese quail (say neural crest) it will develop into the corresponding neural crest derrived parts, and the quail cells are pigmented, so it is easy to see what comes from where (neural crest vs mesoderm) |
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Definition
| what is special about chicken/japonese quail chimeras (surgically transplanted cells)? |
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Term
| we use transgenic mice with special blue staining transgenes (X-gal staining for beta galactosidase) |
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Definition
| how do we tell what develops from neural crest cells now? |
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Term
chordal: is primarily mesoderm
pre-chordal: is primarily neural crest
alongside the notochord is occipital somites |
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Definition
| what is the chordal skeleton developed from? the prechordal skeleton? |
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Term
| caudal: paraxial mesoderm, cranial: neural crest |
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Definition
| bone caudal to the end of the notochord is made of ______, cranial to the end of the notochord is made of _____ |
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Term
| Treacher-Collins Syndrome |
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Definition
| a syndrome that involves deficient development of the facial skeleton |
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Term
| the affected bones all develop from neural crest cells n the 1st and 2nd branchial arches |
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Definition
| what branchial arches are the deficient neural crest cells from in Treacher-collins? |
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Term
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Definition
| med term for small mandible |
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Term
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Definition
| clinical observations include micrognathia, undersized midface, and very undersized or absent zygomatic bones resulting in lateral orbital clefts, may see inferolaterally slanting eyes, deformed external and middle ears |
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Term
1) sufficient number of cells in the initial condensation prior to migration
2) pre-migration condensation must occur at the right time
3) rate of cell division(mitosis) in migrating cells have to be correct
4) the correct proportion of cells need to be mitotically active
5) apoptosis has to occur at the proper time and the proper rate |
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Definition
| to get a normal facial structure ,what 5 things have to go right? |
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Term
mutation in TCOF1, cosed for treacle protein
prevents pre-mature apoptosis of neural crest cells before migration |
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Definition
| what gene mutation cause treacher-colins? what protein does it code for, and what does this protein do? |
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Term
| insufficient number of neural crest cells to begin with (they die too soon with mutated treacle) |
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Definition
| what prevents normal facial structure in treacher-collins? |
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Term
| we compared mice mutants and their mandibles |
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Definition
| how do we know about the TCOF1 gene? |
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Term
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Definition
| what problem is suspected to be caused by signaling problems between mesoderm and neurectoderm? |
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Term
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Definition
| the notochord is derived from _____ and signals back to the nervous system to tell it to develop |
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Term
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Definition
| a condition when the cerebral hemispheres fail to separate, possibly the eyes, and other midline facial structures because the notochord isn't causing proper nervous system development |
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Term
1) anosmia (normal, no sense of smell)
2) single central incisor
3) cleft lip/palate
4) midline facial clefts
5) cebucephaly
6) proboscis
7) synopthalmia
8) cyclopia |
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Definition
| describe the degrees of expression of the holoprosencephaly sequence from the most minor problems to the most severe. |
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Term
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Definition
| signals from MESODERM of the _____ to neurectoderm(ex: the forebrain) are essential for proper brain and eye development |
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Term
| the eyes are outgrowths of the CNS, so the splitting of the CNS into 2 |
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Definition
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Term
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Definition
| what is the main gene telling the |
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Term
| a piece of tissue is in the wrong spot and they have no eyes |
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Definition
| what is synopthalmia with a proboscis? |
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Term
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Definition
| close set eyes and a small nose with a single nostril would be called _____ |
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Term
| cebocephaly is a basicranium problem |
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Definition
| when the brain does not signal the basocranium properly, what condition results that's part of holoprosencephaly? |
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