Embryology Lecture 1
Transcript of Embryology Lecture 1
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Development Growth ( in mass of tissues) Differentiation ( in complexity)
Development does not stop at birth Development of teeth, breast
Brain triples in weigth between birth & 16 yrs Most development completed by the age of 25 Divided into:
Prenatal period (embryonic period: 3rd 8th week) Postnatal period Infancy (neotate 1st yr)
childhood (13 mo 12 yrs) puberty (12 15 , 13 16 yrs) adolescence (12 17 yrs) adulthood (18 21 yrs)
PURPOSE OF LEARNING EMBRYOLOGY.BASIC FACTS OF EARLY HUMAN DEVELOPMENT.
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Literally means study of embryos, 3rd 8th week Generally refers to prenatal development:
both embryos and fetuses. Developmental anatomy: prenatal and postnatal
periods. Teratology: study of abnormal development
(Birth defects, congenital malformations)
DIFFERENCES BETWEEN
CONCEPTUS, EMBRYO, FETUS
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Normal development vs. birth defects Illuminates gross anatomy: normal / abnormal Obstetrics: applied embryology: mother vs
embryo/fetus Pediatrics congenital anomalies: spina
bifida, congenital heart diseases Surgery cleft palate, cardiac defects
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1. Preformation: 18th
century. Development is merely the growth of an
already present diminutive being.2. Epigenesis: (Caspar Friedrich Wolff, 1759)
Development results from growth & differentiationof specialized cells.
3. Recapitulation (Carl Ernst von Baer, 1928):Biogenetic Law
Early stages in devpt are not like the adult stages.
4. Induction (Hans Spemann, 1869-1941): Nobel Prize 1935.Inducer, e.g. optic vesicle lens
(one tissue determines the fate of another)Organizer
Homeoboxes (DNA sequences, encoding AA)
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5. Germ layers Morphogenetic processes - cavitation
- invagination
- migration- proliferationPrimordium (anlage) earliest discernible indication
of an organ or a part of it.6. Epithelio - mesenchymal interactions
skin, hair, nails: Mesenchyme induces & specifies anepithelium.
7. Morphogenetic fields: organizing factorsdetermination: ectoderm neural tissue
8. Morphogenetic processesrearrangement of cells - Relative cell movement
- Cell adhesiveness- Invagination- Condensation- Fusion- Cell death
- Proliferation- Differential growth rates
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9. Cell death (necrosis): genetic control
Interdigital cell deathEstablishment of definite number of neurons cell volume chromatin condensation cell dies
apoptosis autophagy (with / without
lysosomal participation) swelling of a cell & cellular
membrane ruptures
10. Mechanical factors
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Figure 1 : The dwarf embryo as imagined by Leonardo da
Vinci from the 15th century (on the left)
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Figure 7 : Teratoma in the coccygeal region at the end of thespine
Turner's syndrome
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http://embryology.med.unsw.edu.au/Medicine/images/hcriticaldev.gif -
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Trisomy 18: flecked, crossed-over fingers; deformed feet
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Trisomy 13: Cleft palate, lipand jaw
Trisomy 18: Dolichocephaly
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Turner's syndrome
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