Teratogenesis ppt

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TERATOGENESISAMALA SEBASTIAN16PZO-005

TERMSTEROS- MonsterTERATOGEN- An agent that can produce a permanent alteration of structure or function in an organism exposed during embryonic or fetal lifeTERATOLOGY- Branch of science which studies the mechanisms and patterns of abnormal development TERATOGENICITY- the induction of malformation by teratogensTERATOGENESIS-the process by which congenital malformations are produced in an embryo or fetus.

SUSCEPTIBILITY TO TERATOGENESIS DEPENDS UPON:Genotype of the foetus and maternal genomeDevelopmental stages / time of exposureDose and duration of exposureSpecific ways in which a teratogen acts on the developing cellsManifestations of abnormal development death, malformation , growth retardation and functional disorders

THE SENSITIVITY OF THE EMBRYO TO THE TERATOGENIC AGENTS INCLUDE THE FOLLOWINGPRE 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 gestationEMBRYONIC STAGE- stage of intensive differentiation, mobilization and organisation. Therefore embryo becomes more susceptible to teratogens (10-14 days) of generation.

CAUSATIVE FACTORS IN TERATOGENESIS

HEREDITYEXAMPLE:

CLEFT LIP AND PALATE (OROFACIAL CLEFT) SYNDACTYLY

2.ENVIRONMENTThe main environmental factors are teratogens- ALCOHOLBirth defects occur in the children of alcoholic mothersFAS- Fatal Alcohol Syndrome2. DRUGS AND CHEMICALSEthanolRetinoic acidTetracycline }Thalidomide }ANTIBIOTICSStreptomycin }Cigarette smokingHeroin

3. IONIZING RADIATIONRapidly kills the proliferating cellMutagenic agentsX raysMicrocephaly- example

4. PATHOGENS

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 pregnancyHerpes simplex- herpes of the eye, herpes infection of the brain, and neonatal herpes when it affects a newborn, among others

5.MATERNAL DISEASEDIABETICSPHENYLKETONURIAMALNUTRITION

6.HEAVY METALS LIKE MERCURY AND LEADOrganic mercury causes neurological symptoms and Lead can lead to abortion and growth retardation

Types of twins with teratogenic disordersDouble monsters-siamese twinsThe twins are joined or fused together at certain regions of the bodyEqual conjoined twinsUnequal conjoined twins

I. EQUAL CONJOINED TWINSSYMMETRICAL DOUBLE MONSTERS BASED ON THE NATURE OF THE FUSION OF PART OF THE BODY

CRANIOPAGUSTHORACOPAGUSPYGOPAGUS

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HEAD TO HEAD FUSION- CRANIOPAGUS

b).CHEST TO CHEST FUSION- THORACOPAGUS

c).RUMP TO RUMP FUSION- PYGOPAGUS

II. UNEQUAL CONJOINED TWINSHere growth is inhibited or normal differentiation fail to occur in one of the twinsThe smaller individual of a conjoined pair is called parasitic twinNormal part autositeIf the parasitic twin attached to autosite at:

Jaws epignathus parasiticus

b.Thorax thoracopagus parasiticus

c.Rump pygopagus parasiticus

EMBRYOMATAOne kind of mixed tumours containing clearly differentiated organs representing all primary germ layersTERATOMATAAny kind of mixed tumours with tissues or fragmentary parts of organs derived from more than one germ layer but without normal architecture arrangement.

EXAMPLE: DERMATOID CYST

MALFORMATIONS IN LEGS AND ARMSSIRENOMELUSUpper part of the body is normal but the lower part is like tail of fish.

b).AMELIABoth pairs of appendages fail to develop completely

c).PHOCOMELIAHere hand and feet may be attached directly to the trunk due to the failureof the limbs to elongate.

MALFORMATIONS OF HANDS AND LEGSa) POLYDACTYLYDuplication of single digit

b). SYNDACTYLY

Developing digit fail to separate from each other

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

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

GIGANTISMExcessive production of growth hormone

DWARFISMDeficiency in production of growth hormone

REFERENCESDEVELOPMENTAL BIOLOGY- M. A SUBRAMANIAM- PAGE (149-157)DEVELOPMENTAL BIOLOGY SCOTT. F . GILBERT PAGE(666-670)DEVELOPMENTAL BIOLOGY THE FUNDAMENTALS M.G UNIVERSITY

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