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History of embryology
1.
2. Outline
History
Definition of Embryology
Techniques used in Prenatal Screening
(Humans)
Other concepts in embryology
Techniques used in the study of Embryonic
Development
3. History
Embryonic development has been a source
of wonder…
Aristotle’s (384-322 B.C.) studies –a shift
from superstitions to observation.
Galen (130-200 A.D) – learned about
advanced fetuses but the minute dimensions
resisted analysis
4. caused a lag in the growth of knowledge
about the embryo until the development of
microscope.
De Graaf in 1672 – described ovarian follicle
Hamm and Leeuwenhoek in 1677 – have seen
the sperm cells
significance were not understood
5. Theory of Preformation
Spermists - sperm contained new individual in
miniature and only nourished in the ovum
Ovists- thought the same and that the seminal
fluid only stimulates it.
Bonnet (1745) – discovered eggs of some insects
undergoing parthenogenesis
Spallanzani (1729-1799) – demonstrated that
both male and female sex products are
necessary for the initiation of development
6. Wolff (1733–1794) – thesis on epigenesis
(embryological development occurs through
progressive growth and differentiation)
Von Baer (1828) – discovered mammalian egg,
first emphasized that the more general basic
features of any animal group appear earlier in
the development than do special features of
different members of the group – von Baer’s law
Demonstrated existence of germ layers
7. The formulation of cell theory by Matthias
Schleiden and Theodore Schwann laid down
the foundation of modern embryology as a
science.
Ernst Haeckel (1834 -1919) – drafted the
Biogenetic Law of Muller and Haeckel –
Haeckel’s Law of Recapitulation
Ontogeny recapitulates phylogeny
Tail in vertebrates
8.
9. Embryology as a science
Embryology- study of animal development
between fertilization and birth
May include gametogenesis
Weismann (1834-1914) – distinguished
between soma and germ cell
10. Special Fields
Descriptive embryology (1880-1890) – serial
sections and three dimensional wax plate
reconstruction
computer softwares
Comparative embryology (late 1800s) –
provided insights on recapitulation theory;
started with invertebrates (evolution)
11. Experimental – directed to causative factors that
regulate developmental processes.
Chemical embryology – information about the
chemical and physiological events in the embryo.
Included the role of DNA and RNA - how it fabricates
specific chemical and structural components of embryo
12. Teratology – concerned with the study of
malformations
Reproductive biology – problems of
conception and contraception
Developmental biology – approach, includes
even postnatal processes.
13. Prenatal Diagnosis
Designed to detect
Malformations
genetic abnormalities
overall fetal growth
complications of pregnancy, such as placental or
uterine abnormalities.
“Their use and development of in utero
therapies have heralded a new concept in
which the fetus is now a patient. “
14.
15.
16.
17. Ultrasound
may be transabdominal or transvaginal
(produces images with higher resolution)
developed in the 1950s- advanced to
detection of blood flow , movement of heart
valves, fluid flow in the trachea and bronchi
safe and commonly used, with approximately
80% of pregnant women US
18. Ultra…
Parameters revealed :
characteristics of fetal age and growth
presence or absence of congenital anomalies
status of the uterine environment, including the
amount of amniotic fluid (Fig. 7.4A);
placental position and umbilical blood flow;
whether multiple gestations are present
(Fig.7.4B).
Among the factors used to determine proper
approaches for management of the
pregnancy.
19. Fetal age and growth assessed by:
crown-rump length during the fifth to tenth weeks
of gestation.
combination of measurements, including the
biparietal diameter (BPD) of the skull, femur
length, and abdominal circumference (Fig. 7.5).
Multiple measures of these parameters over
time improve the ability to determine the
extent of fetal growth.
20. Congenital malformations determined by
ultrasound:
the neural tube defects anencephaly and spina
bifida
abdominal wall defects, such as omphalocele and
gastroschisis ;
Heart defects
facial defects (cleft lip and palate).
21.
22.
23. Maternal Serum Screening
In search for biochemical markers of fetal
status
first of these tests assessed serum alpha-
fetoprotein (AFP)concentrations.
AFP produced normally by the fetal liver,
peaks at approximately 14 weeks, and “leaks”
into the maternal circulation via the placenta.
24. AFP conc. increase in maternal serum in the
second trim; begin a steady decline after 30
weeks of gestation.
AFP levels increase in amniotic fluid and
maternal serum in
neural tube defects and other abnormalities i.e
omphalocele, gastroschisis, bladder exstrophy,
amniotic band syndrome, sacro-coccygeal
teratoma, and intestinal atresia,
25. AFP conc. decrease in Down syndrome,
trisomy 18, sex chromosome abnormalities,
and triploidy.
During amniocentesis, a needle is inserted
transabdominally into the amniotic cavity
(identified by ultrasound; Fig. 7.4A) and
approximately 20 to 30 ml of fluid are
withdrawn.
26. Amniocentesis
a needle is inserted transabdominally into the
amniotic cavity (identified by ultrasound; Fig.
7.4A)
20 to 30 ml of fluid are withdrawn.
not usually performed before 14 weeks
gestation
risk of fetal loss 1%
27. fluid analyzed for
AFP and acetyl-
cholinesterase
fetal cells in the
amniotic fluid
recovered for
metaphase
karyotyping and
other genetic
analyses
major
chromosomal
alterations, such
as translocations,
breaks, trisomies,
and monosomies,
can be identified.
30. Chorionic villus sampling
CVS involves inserting a needle
transabdominally or transvaginally into the
placental mass and aspirating approximately
5 to 30 mg of villus tissue
Reserved only for high risk pregnancy
31. Fetal Therapy
FETAL TRANSFUSION
In cases of fetal anemia produced by maternal
antibodies or other causes, blood transfusions for
the fetus can be performed. Ultrasound is used to
guide insertion of a needle into the umbilical cord
vein, and blood is transfused directly into the
fetus.
32. FETAL MEDICAL TREATMENT
Treatment for infections, fetal cardiac
arrhythmias, compromised thyroid function, and
other medical problems is usually provided to the
mother and reaches the fetal compartment after
crossing the placenta. In some cases, however,
agents may be administered to the fetus directly
by intramuscular injection into the gluteal region
or via the umbilical vein.
33. FETAL SURGERY
Because of advances in ultrasound and surgical
procedures, operating on fetuses has become
possible.
“Modern medicine has also made the fetus a
patient who can receive treatment, such as
transfusions, medications for disease, fetal
surgery, and gene therapy.”
www.scribd.com/doc/7733260/Langmans-Medical-Embryology
34. Other concepts in
Embryology
Totipotency – capability to form all possible
types of cells - zygote
Pluripotency – all possible cell types with
some exceptions – placental stem cells
Multipotency – multiple types of cells but not
all possible types – adult stem cells
Monopotency – one particular cell type -
monocyte
37. Types of Stem Cell Source Potency
1. Early Embryonic
Stem Cell
Newly fertilized egg
that starts to divide
TOTIPOTENT! They can
become any kind of cell in
the body
2. Blastocyst
Embryonic
Stem Cell
Inner cell mass of
blastocyst (7 days after
fertilization)
PLURIPOTENT! they have
the ability to become
almost any kind of cell in
the body
3. Fetal Stem Cell Fetus ( 8 weeks after
fertilization)
PLURIPOTENT!
4. Umbilical Cord
Stem Cell
Blood from the
umbilical cord
MULTIPOTENT! can
differentiate into only a
limited range of cell types
(blood & immune cells)
5. Adult Stem Cell From developed
tissues
UNIPOTENT!
MULTIPOTENT!
38.
39. Restriction - reduction of developmental
options
Determination – commitment to single
developmental fate
Formation of cornea
Differentiation – formation of specialized cell
49. Culture techniques
Biochemical and molecular techniques
Isoenzymes
PCR
Irradiation techniques
Use of mutants
Transgenic animals
50. References
Carlson B.M. 2003. Patten’s Foundations of
Embryology. 6th
Ed. New York: McGraw-Hill,
Inc. Book Company
www.scribd.com/doc/7733260/langmans-medical
-embryology