USMLE (Fach) / Embryology (Lektion)

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• Neural developent - notochord inducs overlying ectoderm to differentiate into neurectoderm and form neural plate - neural plate gives rise to neural tube and neural crest cells - notochord becomes nucleus pulposus of intervertebral ...
• CNS/PNS origins Neurectoderm - CNS neurons, ependymal cells (inner lining of ventricles, make CSF), oligodendroglia, astrocytes Neural crest - PNS neurons, Schwann cells Mesoderm - Microglia (like macrophages)
• Spina bifida occulta Most common Neural tube defect  - failure of bony spinal canal to close, but no herniation - usually seen at lower vertebral levels - dura is intact - associated with tuft of hair or skin dimple at level ...
• Meningocele Neural tube defect - meninges (but no neural tissue) herniate through bony defect - skin defect/thinning
• Meningomyelocele Neural tube defect - Meninges and neural tissue (e.g. cauda equina) herniate through bony defect - skin thin or absent
• Anencephaly Forebrain anomaly - malformation of the anterior neural tube --> no forebrain, open calvarium - ↑AFP, polydydramnios (no swallowing center in brain) - associated with maternal type 1 diabetes - maternal ...
• Holoprosencephaly Forebrain anomaly - failure of left and right hemisphere to separate - moderate form has cleft lip/palate, most severe form results in cyclopia - seen in Patau syndrom (Trisomy 13) and fetal alcohol ...
• Potter sequence Oligohydramnios --> compression of developing fetus --> limb deformities, facial anomalies (e.g. low-set ears and retrognathia, flattened nose--> compression of chest and lack of amniotic fluid aspiration ...
• Horseshoe kidney - inferior poles of both kidneys fuse abnormally - as they ascend from pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery and remain low in the abdomen - kidneys ...
• Unilateral renal agenesis Uretic bud fails to develop and induce differentiation of metanephric mesenchyme--> complete absence of kidney and ureter
• Multicystic dysplastic kidney Uretic bud fails to induce differentiation of metanephric mesenchyme--> nonfunctional kidney consisting of cysts and connective tissue
• Duplex collecting system Bifurcation of uretic bud before it enters the metanephric blastema creates a Y-shaped bifid ureter - strongly associated with vesicoureteral reflux and/or uretal obstruction, ↑ risk for UTIs
• Kidney embryology Pronephros - degenerates Mesonephros - functions as intermin kidney, later contributes to male genital system Metanephros - permanent- Ureteric bud: derived from caudal end of mesonephric duct, gives ...

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