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HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University

HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University. HUMAN EMBRYOLOGY. Introduction. Tianbao Song ( 宋 天 保 ). 1. What is embryology?. normal development. Twins. Triplets. Congenital malformations(Birth defects).

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HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University

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  1. HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University

  2. HUMANEMBRYOLOGY Introduction Tianbao Song (宋 天 保)

  3. 1. What is embryology? normal development

  4. Twins

  5. Triplets

  6. Congenital malformations(Birth defects)

  7. Embryologyis a science that studies the normal development as well as birth defects of a human being in the maternal uterus.

  8. 2. Historical gleanings Hippocrates : first recordedembryological studies; bird embryo can be likened to that of man. Aristotle: studied chick and other embryos, which resulted from union of semen with menstrual blood. Father of Medicine

  9. Preformation theory Leeuwenhoek : a miniature human being in sperm

  10. Malpighi (1628-1694): a miniature chick in the unhatched egg

  11. Theory of epigenesis Wolff(1733-1794): layer concept (4 layers) Baer: First reported mammalian and human ovum; The 3 germ layer theory; Found notochord; developmental law. Remark (1815-1865): gave names of 3 germ layers Father of Modern Embryology

  12. Darwin (1859): On the Origin of Species emphasized thehereditary nature of variability in evolution. Recapitulation theory Müller and Haeckel(1860’): Ontogeny is a brief recapitulation of phylogeny.

  13. Hans Spemann (1869-1941): theory of organizer andembryonic induction. Noble prizewinner in medicine and physiology (1935). Needham(1900-1995): chemical embryology

  14. Progressof modern embryology: Test tube babies Edwards,Steptoe (1978): first TTB in the world (Louise Brown) Zhang Lizhu, Liu Bin(1988): first TTB in China (Zheng Mengzhu)

  15. Somatic cell Cloned animals Wilmut & Campbell (1997): first cloned sheep in the world(Dolly)

  16. 3. Normal development 38 weeks from fertilization to parturition 1)Preembryonic period: First 2 weeks;Fertilization to formation of the bilaminar germ disc.

  17. 2) Embryonic period: Weeks 3 - 8; Primordia of all major organs develop from the 3 germ layers.

  18. 3) Fetal period:Week 9 – birth. Growth of the organ systems

  19. 4. Birth defects 4.1 Definition: structural and functional defects present at birth (congenital malformations). teratology: study of congenital malformations • 4.2 Causes • 1) Genetic factors (25%) • 2)Environmental factors(teratogens) (10%) • 3)Interaction of genetic and environmental • factors (65%)

  20. 4.2.1 Genetic factors 1) Numerical abnormalitiesof chromosomes Autosomes -- Trisomy 21 (Down’s syndrome):

  21. Down’s syndrome: special face, mental retardation, heart defect, simian crease.

  22. Sex chromosomes Turner’s syndrome (XO): short stature webbed neck no ovary mental retardation

  23. Klinefelter’s syndrome (XXY): testicular atrophy sterility gynecomastia (mental impairment)

  24. 2) Structural abnormalities of chromosomes: break, deletion, insertion, etc. e.g.: 5p- → cat cry syndrome 3) Mutationsof genes metabolic or functional disorders (e.g. phenylketonuria, galactosemia); a few malformations(e.g. microcephaly, achondroplasia, polycystic kidney)

  25. 4.2.2. Environmental factors (teratogens) • 1) Biological • Viruses: • rubella virus→ cataracts, deafness, cardiac defects; • cytomegalovirus→blindness, microcephaly, hepatosplenomegaly; • herpes simplex virus→ microcephaly, microphthalmus. • Toxoplasma gandii (Toxoplasmosis) • Treponema pallidum(Syphilis) • Chlamydia trachomatis, ureplasma urealyticum

  26. 2) Physical radiation, mechanical pressure, traumas Radiation: World War II: atomic bomb explosion over Japan. Survived pregnant women: 28% aborted; 25% delivered children died <1 year; 25% infants with CNS malformations.

  27. 3) Chemical • chemicals: nitrite, benzol; lead, arsenic, cadmium, mercury, etc. • drugs: thalidomide (amelia and meromelia),

  28. aminopterin (anencephaly, hydrocephalus, cleft lip), streptomycin (deafness). hormones: estrogens, progestins social drugs: cigarettes (small babies), alcohol (fetal alcohol syndrome).

  29. 4) Others hypoxia(small babies); nutritional deficiencies (Vitamins, iodine). 4.2.3. Interaction of genetic and environmental factors: (Cleft lip, heart defect, spina bifida…)

  30. 4.3 Susceptible period 1) Dependent on the developmental stage. The embryonic period (weeks3-8) is highest susceptible because of intensive differentiation.

  31. 2) Different organs have different susceptible period corresponding to their own critical development stage.

  32. 3) Different teratogens also have different susceptible period. Rubella virus:1st month 50%; 2nd month 22%; 3rd month 7%. Thalidomide:20 days after gestation

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