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(마더세이프라운드) Embryogenesis - 제일병원 전이경 선생


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(마더세이프라운드) Embryogenesis - 제일병원 전이경 선생

  1. 1. Human Embryology제일병원 병리과 전이경
  2. 2. Critical periods of development for various organsystems and the resultant malformations
  3. 3. First week of development:ovulation to implantationblastocystmorule
  4. 4. 4.5 days 6 days
  5. 5. Second week of development:bilaminar germ discWeek of twos• Inner cell mass (embryoblast)– Epiblast– Hypoblast• Trophoblast– Cytotrophoblast– Syncytiotrophoblast• Extraembryonic mesoderm– Somatopleuric mesoderm– Splanchnopleuric mesoderm• Two cavities– Amniotic cavity– Yolk sac• Uteroplacental circulation12 daysAmnioticcavity
  6. 6. Day 13
  7. 7. Third week of development:Trilaminar germ discGastrulation• Bilamelar germ disc isconverted into atrilamelar germ– Ectoderm– Mesoderm– Endoderm• Primitive streak– Thickened linear band ofepiblast– 15- to 16-day embryo:clearly visible
  8. 8. Epiblast ->1. ectoderm2. mesoderm3. endoderm18-day embryo1.25 mm in length
  9. 9. Derivatives of the ectodermal germ layer1. Central nervous system2. Peripheral nervous system3. Skin, including hair and nails4. Sensory epithelium of ear, nose, and eye5. Pituitary, mammary, and sweat glands andenamel of the teeth
  10. 10. Derivatives of the mesodermal germ layer• Connective tissue,cartilage, bone andstriated and smoothmuscles• heart, blood and lymphvessels and cells• kidney, ovary and testis,genital ducts, serousmembranes lining, spleen,and adrenal cortex
  11. 11. Derivatives of the endodermal germ layer1. Epithelial lining of thegastrointestinal tract,respiratory tract, andurinary bladder2. Parenchyma of thethyroid, parathyroid,liver and pancreas3. Epithelial lining of thetympanic cavity andauditory tube
  12. 12. Fate of the primitive streak• intraembryonic mesoderm 을4주말까지 만들다가 감소• insignificant structures in thesacrococcygeal region of theembryo• Sacrococcygeal teratoma
  13. 13. Teratogenesis associated withgastrulation• The beginning of the third week of development,when gastrulation is initiated, is a highly sensitivestage for teratogenic insult.• At this time, fate maps can be made for various organsystems, such as the eyes and brain anlage, andthese cell populations may be damaged byteratogens.• For example, high doses of alcohol at this stage killcells in the anterior midline of the germ disc,producing a deficiency of the midline in craniofacialstructures and resulting in holoprosencephaly.
  14. 14. Caudal dysgenesis (sirenomelia)• Insufficient mesodermin the lumbosacralregion of the embryo− Hypoplasia andfusion of lower limb− Vertebralabnormalities− Renal agenesis− Imperforate anus− Anomalies of thegenital organs
  15. 15. Formation of the notochordB C
  16. 16. Notochord:1. Primitive axis of the embryo2. Induction - neural plate (futurenervous system)Fate of the Notochord:– Regress in the vertebral bodies– Intervertebral disc: persist as thenucleus pulposus
  17. 17. 20 daysNeurulation includesthe formation of the neuralplate (day 18-19), neuralfolds (day 20-21), and theneural tube (day 22-26); thelatter will develop into thefuture brain and spinalcord
  18. 18. Final closureAnterior neuropore: 25th dayPosterior neuropore: 27th day
  19. 19. Neural tube defects• Most common CNS malformation,1/1000 births• Primary non-close of the neural tube• Spectrum– Anencephaly– Meningocele– Meningoencephalocele– Meningomyelocele
  20. 20. Anencephaly• Absence of scalp, calvarium,and normal brain -> “frog’sface”• Area cerebrovasculosa• Hypoplastic adrenal glandswith absent fetal zone• Recurrence rate: 3-5%• DDx: amniotic disruptionsequenceAmniondisruptionconsequenceAnencephaly
  21. 21. Holoprosencephaly4th week, 4mm, 3 vesicle stage 5th week, 8 mm, 5 vesicle stage
  22. 22. Lissencephaly• “Smooth brain”• Severity : the absence(agyria) to reduction(pachygyria) of normalgyral pattern.• Classic L./cobblestone L.• Onset : no later than the12th–16th week ofgestation• DDx: immature GA (until27-28W)•GA 31 wks•46, XX, del(17)(p13)•“Miller-Dieker” syndrome
  23. 23. Formation and migration of neural crest cells in the spinal cord
  24. 24. Neural crest cells• Vulnerable cell population• Easily killed by compounds such as alcohol and retinoic acid.• Deficient in superoxide dismutase and catalase enzymes thatare responsible for scavenging free radicals.• Neural crest derivatives Connective tissue and bones of the face and skull Dermis in face and neck☞ Severe craniofacial malformations☞ Treacher-Collins Syndrome, DiGeorge anomaly... Conotruncal septum in the heart☞ cardiac anomalies including persistent truncus arteriosus,TOF and TGA Cranial nerve ganglia, spinal ganglia, sympathetic chain andpreaortic ganglia, parasympathetic ganglia of thegastrointestinal tract, glial cells, schwann cells, adrenalmedulla, C cells of the thyroid gland, arachnoid and piamater, melanocytes, odontoblasts
  25. 25. Neural crest cells in conotruncal region
  26. 26. MIGRATION PATHWAYS OFNEURAL CREST CELLSfrom forebrain, midbrain,and hindbrain regions intotheir final locations (shadedareas) in the pharyngealarches and faceSkeletal structures of thehead and face. Mesenchymefor these structures isderived from neural crest(blue), lateral platemesoderm (yellow), andparaxial mesoderm (red).
  27. 27. Treacher-Collins Syndrome /mandibulofacial dysostosis• Characterized by malarhypoplasia due tounderdevelopment of cheekbones, mandibularhypoplasia, down-slantingeyes and malformedexternal ears• Normal development andintelligence• AD with variable penetrance• 60% as new
  28. 28. Velocardiofacial Syndrome/DiGeorge anomaly• 22q11.2 deletion• “CATCH 22”– Cardiac defects– Abnormal face– Thymic hypoplasia– Cleft palate– Hypocalcemia• Abnormal development ofneural crest cells• Specific facial features– low-set ears, wide-set eyes,a small jaw, and a shortgroove in the upper lip• Etiology– Genetic causes, exposure toretinoic acids, alcohol, andmaternal DM
  29. 29. Limb growth and developmentA. 5-week embryo B. 6-week embryo C. 8-week embryoThe hindlimb buds are less well developed than those of theforelimbs.The most sensitive period for teratogen-induced limbmalformations is the fourth and fifth weeks of development
  30. 30. Nasal pitLateral nasalprominenceMedial nasalprominence5주10주7주6주
  31. 31. A.B. 6.5-week embryoThe palatine shelvesare in the verticalposition on each sideof the tongue.C.D. 7.5-week embryoThe tongue hasmoved downward,and the palatineshelves have reacheda horizontal position.E.F. 10-week embryoThe two palatineshelves have fusedwith each other andwith the nasal septum.C DFE
  32. 32. A, day 18B, day 20C, day 21D, day 22*Heart tube
  33. 33. Atrial Septation (4-6 weeks)Septum primumostium primumInterventricularforamen
  34. 34. ostiumsecundumSeptumsecundum35 days
  35. 35. Development of conotruncal ridges andclosure of the interventricular foramen6 weeks Beginning of 7 weeks
  36. 36. End of 7 weeks
  37. 37. Third to eighth week:The embryonic period• Period oforganogenesis• Each of three germlayers gives rise toits own tissues andorgans.• Major features of theexternal body formrecognizable by theend of the secondmonth