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55 Cards in this Set

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mesoderm derived tissue along the axis of the embryo resposible for forming somites (caudally from head region) and somiteres (in head region) on each side of the neural tube. The skeletal system develops from here.
Paraxial plate mesoderm (somatic layer)
mesoderm derived tissue that splits into splanchnopleure (visceral) and somatopleure (somatic) layers surrounding organs and body cavity. the skeletal system develops from here.
lateral plate mesoderm (somatic layer)
early neuroepithelial embryonic development, the cells of which migrate and differenciate into various cell types. These cells are vulnerable to teratogenic insult. The skeletal system develops from here.
Neural Crest
somites and somiteres develop in ...
segments
loosely organized segmented collections of paraxial mesoderm in the cranial region. _____ form muscles and bones in the face and skull
somitomeres
epithelial balls of cells formed in segmental pairs along the neural tube from paraxial mesoderm. _____differentiate into vertebrae, muscles of the back and body wall and dermis of the skin and parts of the cranium.
somites
ventromedial part of each somite that forms the vertebrae
sclerotome
dorsolateral development of each somite
dermomyotome
any loosely organized tissue composed of fibroblast-like cells and extracellular matrix regardless of the origin of the cells. These cells migrate and differentiate into many cell types (fibroblasts, osteoblasts, chondroblasts..etc). Also known as embryonic connective tissue.
mesenchyme
bone forming cells
osteoblasts
process of mesenchyme directly differentiating into bone, seen in the flat bones of the cranium
Intramembranous ossification
occur a six weeks of gestation. mesenchymal cells usually develop cartilage models before forming bone via endrochondral ossification
hyaline cartilage models
mechanism for forming bone by first establishing a carlaginous model followed by ossification. This type of bone formation is characteristic of the bones of the limbs and base of the skull
endochondral ossification
part of the skull that forms a protective case around the brain (the other part of the skull is the viscerocranium or face). It consists of two parts, the membranous neurocranium, or flat bones of the skull and the cartilaginous neurocranium or chondrocranium, forming the base of the skull.
neurocranium
forms from paraxial mesoderm and neural crest cells. These cells form the cranium via membranous ossification
membranous neurocranium
part of the skull that comprises the bones of the face
viscerocranium
consist of a layer of spongy bone between two thin layers of compact bone.have marrow, but not a bone marrow cavity. They form protective cases for viscera.
flat bones
part of the neurocranium that forms the base of the skull and that arises by first establishing cartilage models for the bones (endochondral ossification)
chondrocranium
process of forming bone directly from mesenchyme. This process is characteristic of the flat bones and the cranial vault.
membranous ossification
found on the flat bones which result from membranous ossification in skull region. The ______progressively radiate out from ossification centers.
bone spicules
narrow seams of connective tissue, which separate the flat bones of the skull at birth.
sutures
points at which more than two flat bones meet and the resulting sutures are wide.
Fontanelles
most prominent fontanelle found on newborn. Found where two parietal bones meet two frontal bones
anterior fontanelle
process of overlapping of flat bones during birth, possible due to the sutures
molding
cartilages which are precursors to base of skull found anterior to future sella turcica. Develops from neural crest cells
prechordal chondrocranium
cartilages which are precursors to the base of the skull found posterior to the future sella turica. Develops from the paraxial nesoderm.
chordal chondrocranium
portion of a dorsal pharyngeal arch which forms a portion of the viscerocranium: maxilla, zygomatic bone and part of the temporal bone.
maxillary process
lower jaw bone
maxilla
portion of a ventral pharyngeal arch which containes the Meckel cartilage. Dorsal tip also gies rise to the incus, malleus and stapes.
mandibular process
ossifies via membranous ossification and forms the mandible. It disappears except in the sphenomandibular ligament.
mechel cartilage
develop much of the face and skull. Originate from the neuroectoderm.
neural crest cells
cells of the neuroepithelium that form the tips of the neural folds and then migrate to other regions for form many structures, including spinal ganglia, bones and connective tissue of the face, septa for the outflow of tract of the heart, some cranial nerve ganglia, ganglia for the gut tube (enteric ganglia), melanocytes, etc…. These cells are vulnerable to teratogenic insult and provide a rational for why many children with facial clefts also have cardiac defects.
neural crest cells
cranial vault does not close, so brain tissue is exposed to brain fluid, which degenerates it. The result is anencephaly.
Cranioschisis
Neural tube defect in which the cranial folds fail to close, leading to tissue degeneration and little or no formation of higher brain centers, cerebral cortex…etc. The abnormality is lethal, 70% of these defects can be prevented by daily maternal use of 400ug of folic acid, beginning 2-3 months prior to conception and continueing throughout pregnancy.
Anencephaly
neural tube defect in which a sac of fluid filled meninges protrudes through an opening in the skull. This is treatable.
Cranial meningocele
collection of abnormalities, in which sutures close prematurely.
Craniosynostosis
f the saggital suture closes prematurely and the parietal and occipital bone become long and narrow
Scaphocephaly
premature closure of coronal suture results in a short, high skull.
Acrocephaly (Tower skull)
premature closure of lamboid and coronal sutures, which results in short skull
Brachycephaly
derived from paraxial mesodermal germ layer, which forms from the somites and somitomeres
Skeletal muscle
most is derived from the paraxial mesodermal germ layer. ______develops from splanchnic mesoderm and from ectoderm
smooth muscle
derived from splanchnic mesoderm (surrounding the heart tube), as well
cardiac muscle
mesoderm derived tissue along the axis of the embryo responsible for forming somites and somitomeres.
paraxial mesoderm
site of muscle formation, cells from here contribute to myotome formation. Also provides cells for limb and body wall formation
Ventrolateral edge or lip (VLL) of dermomyotome
musculature derived from the dorsolateral portion of each somite that forms muscles of the anterior body wall
Hypomeric musculature
second region of muscle formation; cells travel ventral and contribute to the formation of myotome
Dorsomedial edge or lip (DML) of the dermomyotome
dorsal musculature derived from the myotome portion of each somite that forms the extensor muscles of the back
Epimeric musculature
muscle forming cells. Fuse to make multinucleated muscle tissue
myoblasts
derived from sclerotome cells adjacent to myotomes at the ant/post borders of the somites
tendons
regulates the development of sclerotome cells adjacent to myotomes
scleraxis
at the end of the fifth week prospective muscle is either here or in the hypomere; the ____is in the dorsal region; this is formed by the dorsomedial somite cells of myotomes
epimere
this is larger and in the ventral region, formed by migration of the dorsolateral cells. Gives rise to muscles of limbs and body wall
hypomere
branch of a spinal nerve that innervates muscles derived from the epimere and skin over the back
dorsal primary ramus
ventral branch of a spinal nerve that innervates muscles derived from the hypomere and skin over the anterior body wall and limbs.
ventral primary ramus
formed by myoblasts of the epimere
extensor muscle