TERATOGENESIS IN DEVELOPMENTAL BIOLOGY

1. AMALA
SEBASTIAN
16PZO-005

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

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.

9. 1. HEREDITY
EXAMPLE:
1)CLEFT LIP AND PALATE
(OROFACIAL CLEFT)
2)SYNDACTYLY

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

13. 3. IONIZING RADIATION
•Rapidly kills the proliferating cell
•Mutagenic agents
•X rays
•Microcephaly- example

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

15. 5.MATERNAL DISEASE
a)DIABETICS
b)PHENYLKETONURIA
c)MALNUTRITION

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

19. a) HEAD TO HEAD FUSION- CRANIOPAGUS

20. b).CHEST TO CHEST FUSION- THORACOPAGUS

21. c).RUMP TO RUMP FUSION- 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:

23. a.Jaws – epignathus parasiticus

24. b.Thorax – thoracopagus parasiticus

25. c.Rump – pygopagus parasiticus

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.

28. EXAMPLE: DERMATOID CYST

29. MALFORMATIONS IN LEGS AND ARMS
a) SIRENOMELUS
Upper part of the body is normal but the lower part is like tail of fish.

30. b).AMELIA
Both pairs of appendages fail to develop completely

31. c).PHOCOMELIA
Here hand and feet may be attached directly to the trunk
due to the failure
of the limbs to elongate.

32. MALFORMATIONS OF HANDS AND LEGS
a) POLYDACTYLY
Duplication of single digit

33. b). SYNDACTYLY
Developing digit
fail to separate
from each other

34. c).OLIGODACTYLY
Failure of
development of
one or more digit

35. PERSISTENCE OF TAIL
Instead of
regression,
tail
continues to
grow and
persist even
in adult
stage.

36. GIGANTISM
Excessive production of growth hormone

37. DWARFISM
Deficiency in
production of
growth
hormone

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