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42 Cards in this Set
- Front
- Back
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Embryonic Period
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Weeks 3-8 of prenatal development
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Cleavage
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Week 1 of prenatal development; zygote undergoes successive cell divisions without growth
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Fetal Period
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Week 9-> birth;
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Morula
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16-32 cells produced during cleavage; formed from blastomeres that undergo compaction
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Blastocyst
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formed during cleavage as morula hollows; forms trophoblast and inner cell mass
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Trophoblast
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forms chorion; part of placenta
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inner cell mass
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forms embryo and other extraembryonic membranes
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Implantation
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occurs during 1st week; trophoblast cells digest into endometrium of uterus; inner cell mass segregates into epiblast (top layer) and hypoblast (bottom layer)
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Amniotic Cavity
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fluid-filled space between epiblast and trophoblast
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Bilaminar embryoblast
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cells of epiblast & hypoblast in contact
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Trilaminar embryoblast
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Occurs during 3rd week; Part of gastrulation; Epiblast cells move toward primitive node & primitive streak
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During gastrulation, cells of epiblast ingress through streak to become:
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endoderm (displacing hypoblast), mesoderm, ectoderm
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During gastrulation, what population of cells forms along the midline from the primitive node?
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notochordal process
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When notochordal process changes from tube to rod, it becomes the.....
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notochord
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3 types of mesoderm
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1. paraxial mesoderm - adjacent to notochord
2. intermediate mesoderm 3. lateral plate mesoderm (coelom forms here) |
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Through neural induction, notochord instructs ectoderm to form.....
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neuroectoderm
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Neural crest contributes to what structures?
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peripheral nervous system, many other structures
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Closure of anterior and posterior neuropore occur at what fetal age?
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25-26 days
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What structures are formed from ectoderm?
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brain, spinal cord (neuroectoderm), epidermis, hair, nails, cutaneous glands, enamel (surface ectoderm)
- neural crest forms peripheral nervous system and lots of other structures!! |
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What structures form from paraxial mesoderm?
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bone/cartilage/connective tissue, muscle, dermis
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What structures are formed from intermediate mesoderm?
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parts of urinary system and gonads
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What structures are formed from lateral plate mesoderm?
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- somatic layer = forms limb skeleton, part of body wall
- splanchnic layer = forms most of the gut, except its lining |
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Endoderm forms...
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GI tract, lungs, liver/gall bladder/pancreas, urinary bladder
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Intramembranous ossification
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Direct ossification of mesenchyme
- examples: many bones of skull, sesamoid bones |
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Endochondral ossification
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Formation of a cartilaginous template that is replaced by bone
- examples: most bones of postcranial skeleton, base of skull |
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3 major divisions of somites:
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1. dermatome: dermis of back
2. myotome: skeletal muscle 3. sclerotome: cartilage and bone |
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What bones re-segment to lie intersegmentally?
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Vertebrae & ribs
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Cells that surround the neural tube form the...
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vertebral arch
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Cells that surround the notochord form the...
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vertebral body
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Cells that migrate laterally form the...
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ribs or costal elements
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3 primary ossification centers of vertebrae
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one for each side of the neural arch, one for the vertebral body
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Notochord may contribute to which part of intervertebral disc?
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Nucleus pulposus
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Sclerotomal cells that do not contribute to adjacent vertebral bodies form...
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annulus fibrosis
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Posterior neuropore closes at what vertebral level?
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Lower sacral levels
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Ribs develop from...
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sclerotome cells that migrate into somatic lateral plate mesoderm
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The sternum forms...
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from bilateral edges of the somatic lateral plate mesoderm
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Myotomal cells separate from dermamyotome migrating dorsally to form....
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epimere
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Myotomal cells migrate ventrally to form...
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hypomere
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Cells of epimere become what muscles?
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epaxial (intrinsic back muscles)
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Cells of hypomere become what muscles?
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Hypaxial muscles, including limb muscles
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Somatic LPM forms:
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body wall of embryo
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Localized proliferation of LPM results in...
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limb bud
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