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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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Dept. of Anat., Hist. & Embry.
School of Medicine
Xi’an Jiaotong University
Tianbao Song (宋 天 保)
Embryologyis a science that studies the normal development as well as birth defects of a human being in the maternal uterus.
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
Leeuwenhoek : a miniature human being in sperm
Wolff(1733-1794): layer concept (4 layers)
Baer: First reported mammalian and human ovum;
The 3 germ layer theory;
Remark (1815-1865): gave names of 3 germ layers
Father of Modern Embryology
Darwin (1859): On the Origin of Species emphasized thehereditary nature of variability in evolution.
Müller and Haeckel(1860’): Ontogeny is a brief recapitulation of phylogeny.
Noble prizewinner in medicine and physiology (1935).
Needham(1900-1995): chemical 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)
Wilmut & Campbell (1997): first cloned sheep in the world(Dolly)
38 weeks from fertilization to parturition
1)Preembryonic period: First 2 weeks;Fertilization to formation of the bilaminar germ disc.
2) Embryonic period: Weeks 3 - 8; Primordia of all major organs develop from the 3 germ layers.
Growth of the organ systems
4.1 Definition: structural and functional
defects present at birth (congenital
teratology: study of congenital malformations
1) Numerical abnormalitiesof chromosomes
Autosomes -- Trisomy 21 (Down’s syndrome):
Turner’s syndrome (XO):
break, deletion, insertion, etc.
e.g.: 5p- → cat cry syndrome
3) Mutationsof genes
metabolic or functional disorders (e.g.
a few malformations(e.g. microcephaly,
achondroplasia, polycystic kidney)
radiation, mechanical pressure, traumas
Radiation: World War II: atomic bomb
explosion over Japan.
Survived pregnant women:
25% delivered children died <1 year;
25% infants with CNS malformations.
hormones: estrogens, progestins
social drugs: cigarettes (small babies),
alcohol (fetal alcohol syndrome).
4.2.3. Interaction of genetic and environmental factors: (Cleft lip, heart defect, spina bifida…)
1) Dependent on the developmental stage.
The embryonic period (weeks3-8) is
highest susceptible because of intensive
2) Different organs have different susceptible period corresponding to their own critical development stage.
Rubella virus:1st month 50%;
2nd month 22%;
3rd month 7%.
Thalidomide:20 days after gestation