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40 Cards in this Set
- Front
- Back
What is the Pre-embryonic Period? |
Zero - 2 weeks |
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What occurs when a zygote develops |
Series of mytotic divisions --> morula (ball of cells) Intercellular spaces consolidate to forma cavity and inner cells move to one pole (embryoblast) |
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What is a Blastocyst? |
Outer epithelial wall and attaches to the uterine wall |
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What occurs during Wk 2 of the Pre-Embry |
Bilaminar Germ Disc formation - Uteroplacental circullaion is est -Inner cell mass differentiates into two layers |
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What are the two layers of the inner cell mass? |
Epiblast - amniotic cavity develops here Hypoblasts - exocoelomic cavity -later produces cells that forms the smaller yolk sac |
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When is the Embryonic period? |
3-8weeks Greatest susceptibilty to teratogensis (outside influences) |
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What occurs during week 3? |
Trilaminar germ disc formation -Gastration occurs - 3 germ layers est |
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What is the primitive streak? |
Forms on surface of epiblast Primitive node forms near P. Streak cephalic end |
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How do Epiblast cells travel in week 3? |
Invaginate in the primitive pit and travel rostrally to form the definitive notochord Migrate through the steak to form endoderm and mesodern. some remain as ectoderm |
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What is the notochord? |
Serves as basis for the axial skeleton |
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What are the major accomplishments of wk 3-8 |
Periodof organogenesis where ectoderm, mesoderm, and endoderm give rise to specifictissues and organs, establishing major features of body form. |
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Describe the Endoderm? |
Forms epithelial lining of resp, gasto, and urinary bladder Forms parenchyma of thyroid gland liver and pancreas Tympanic cavity and eustachian tube |
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Describe the Mesoderm
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Tendon, Cartilage, bone, and skin Forms urogenital structures (intermediate mesoderm) Lateral Plate - lateral and ventral body wall, wall of gut |
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Describe the ectoderm? |
Gives rise to structures that maintain contact with the outside world Epidermis Sensory epithelium of eye, ear, nose CNS and PNS |
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When does the Neural tube form? |
Week 3-4 |
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What forms the neural plate? |
Thickened ectoderm dorsal to the notochord |
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What forms the neural folds and groove? |
Lateral edges thicken forming folds and with a depressed midregion |
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What is a neural crest cell? |
Appears along edge of neural folds and give rise to important PNS structures |
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What do neural crest cells differentiate into |
Dorsal root and cranial nerve sensory ganglia neurons Post ganglionic and enteric visceromotor neurons Schwann cells - myelination in PNS Chromaffin - adrenal medulla Melanocyte - pigment Pia and arachnoid mater |
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How is the neural tube formed? |
When nueral fold fuse in the mid line proceeds cranially and causdally in a zipper like fashionl |
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When do the neuropores close? |
Anterior neuropore - 24-26 Posterior Neuropore - 25-28 |
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How to help prevent neural tube defects |
Folic acid during pregnancing |
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Describe Arnold-Chiari Malformation |
Often occurs at the anterior neuropore Cerebellar vermis herniates through the formen magnum and compresses the medula and C-Spine |
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Define Spina Bifida |
Defects involving the closure of the posterior neuropore - myeloschisis Vertebral arch fails to form completely and fuse |
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What is spina bifida occulta |
Mildest form - Skin closes over the top Affects up to 10% of other wise normal individuals - often marked by a patch of hair |
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Describe Spina Bifida Cystica |
Has accompanying cystic mass Meningocele - meninges and CSF Meningomyelocele - meninges, CSF, and spinal cord 5/10kbirths |
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What are the causes of spinal bifida cystica |
Often are accompanied by hydrocephalus because of associated spinal cord adhesion to the vertebral column and Arnold chiari malformation |
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Primary vs Secondary Neurulation |
P: Formation down to S2 S: Sacral and Coccygeal |
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What is tethered cord syndrome |
Form of myelodysplasia - defect of secondary neurulation. Bottom of SC and Filum Term are abnormallt fixed to the defective vertebral column Progressive |
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What can tension in the spinal cord result in? |
Weakness of the lower limb, sensory deficits, pain, and loss of bladder control |
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What are the three primary brain vesicles the neural tube differentiates into |
Prosencephalon - forebrain Mesencephalon - midbrain Rhombencephalon - Hind brain |
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What are neuroepithelial cells? |
Form pseudostratified epithelium and makes up the wall of the neural tube |
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What occurs during transverse differentiation |
-Dorsal and ventral thickening of the lateral wall
-Alar and basal plates -Sulcus Limitans little is differentiated in midorsal/ventral areas |
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What does the Alar plate give rise to? |
Sensory Neurons Cerebellum Thalamus Basal Nuclei Cerebral Cortex |
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What does the Basal Plate give rise to? |
Motor Neurons Hypothalamus Retina |
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What do neuroepithelial cells differentiate into |
Neuroblasts and gliablasts
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How do neurons mature? |
Axonal growth, dendrite development, synaptogenisis |
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What do Glialblasts differentiate into? |
Astrocytes, oligodendrocytes, and ependymal cells |
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Describe Radial Glia |
Present during development but ultimately differentiate into astrocytes Provide scaffold that is critical for guiding migration of immature neurons during the formation of the cerebral cortex |
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What cellular events occur postnatally? |
Development of the nervous system -Neuronal density -Neuronal process branching and myelination -pattern of synaptic contacts |