2. TERMS
TEROS- Monster
TERATOGEN- An agent that can produce a
permanent alteration of structure or function in an
organism exposed during embryonic or fetal life
TERATOLOGY- Branch of science which studies
the mechanisms and patterns of abnormal
development
TERATOGENICITY- the induction of malformation
by teratogens
TERATOGENESIS-the process by which
congenital malformations are produced in an embryo
or fetus.
3. SUSCEPTIBILITY TO TERATOGENESIS
DEPENDS UPON:
1.Genotype of the foetus and maternal
genome
2.Developmental stages / time of exposure
3.Dose and duration of exposure
4.Specific ways in which a teratogen acts on
the developing cells
5.Manifestations of abnormal development –
death, malformation , growth retardation and
functional disorders
4.
5.
6.
7. THE SENSITIVITY OF THE EMBRYO TO
THE TERATOGENIC AGENTS INCLUDE
THE FOLLOWING
PRE DIFFERENTIATION STAGE- the embryo is
not susceptible to teratogens. The teratogens may
either cause death of the embryo by killing all or
most of the cells or they may have no apparent
effect on embryo. Resistant strain ( 5-9 days ) of
gestation
EMBRYONIC STAGE- stage of intensive
differentiation, mobilization and organisation.
Therefore embryo becomes more susceptible
to teratogens (10-14 days) of generation.
11. 2.ENVIRONMENT
The main environmental factors are teratogens-
1.ALCOHOL
Birth defects occur in the children of alcoholic
mothers
FAS- Fatal Alcohol Syndrome
2. DRUGS AND CHEMICALS
a)Ethanol
b)Retinoic acid
c)Tetracycline }
d)Thalidomide }ANTIBIOTICS
e)Streptomycin }
f) Cigarette smoking
g)Heroin
14. 4. PATHOGENS
1)Rubella virus-german measles-Symptoms of CRS
include problems with the eyes such as cataracts, ears such as deafness,
heart, and brain. Problems are rare after the 20th week of pregnancy
2)Herpes simplex- herpes of the eye, herpes infection of the
brain, and neonatal herpes when it affects a newborn, among others
16. 6.HEAVY METALS LIKE MERCURY AND LEAD
Organic mercury causes neurological
symptoms and Lead can lead to
abortion and growth retardation
17. Types of twins with teratogenic disorders
Double monsters-siamese twins
The twins are joined or fused together at certain regions of the
body
I. Equal conjoined twins
II. Unequal conjoined twins
18. I. EQUAL CONJOINED TWINS
SYMMETRICAL DOUBLE MONSTERS
BASED ON THE NATURE OF THE FUSION OF PART OF THE BODY
a) CRANIOPAGUS
b) THORACOPAGUS
c) PYGOPAGUS
22. II. UNEQUAL CONJOINED TWINS
Here growth is inhibited or normal
differentiation fail to occur in one of the twins
The smaller individual of a conjoined pair is
called parasitic twin
Normal part – autosite
If the parasitic twin attached to autosite at:
27. EMBRYOMATA
One kind of mixed tumours containing clearly
differentiated organs representing all primary germ
layers
TERATOMATA
Any kind of mixed tumours with tissues or
fragmentary parts of organs derived from
more than one germ layer but without normal
architecture arrangement.
40. REFERENCES
I. DEVELOPMENTAL BIOLOGY- M. A
SUBRAMANIAM- PAGE (149-157)
II. DEVELOPMENTAL BIOLOGY – SCOTT. F .
GILBERT – PAGE(666-670)
III.DEVELOPMENTAL BIOLOGY – THE
FUNDAMENTALS – M.G UNIVERSITY
