Teratogenesis ppt
- 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
- 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.
- 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
- 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