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TERATOLOGY & EMBRYOLOGY

BYDR. ABDUL WAHEED ANSARI

CHAIRPERSON &PROF. ANATOMYRAK COLLEGE OF MEDICAL SCIENCES

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If normal embryology is disturbed

• It resulted in teratology. It is the study of abnormal congenital development resulting in defects and monsters.

• Teratogens can be mechanical, thermal, drug induced, bacterial or viral induced or radioactive induced.

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Cleft lip & cleft palate

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Cleft lip/palate is a congenital deformity

• Caused by abnormal facial development during gestation.

• A cleft is a fissure or opening—a gap.• It is the non-fusion between the frontonasal

process with the maxillary processes.• Approximately 1 in 700 children born have a

cleft lip and/or a cleft palate.

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Tutankhamen

• Egyptian pharaoh who may have had a slightly cleft palate according to diagnostic imaging.

• The research also showed that the Tutankhamen had "a slightly cleft palate" and possibly a mild case of scoliosis, a medical condition in which a person's spine is curved from side to side.

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During the first six to eight weeks of pregnancy

• Embryo's head is formed, & Five prominences grow:• One from the top of the head down towards the

future upper lip; (Frontonasal Prominence)• Two from the cheeks, which meet the first

prominence to form the upper lip; (Maxillary Prominence)

• Just below, two additional prominences grow from each side, which form the chin and lower lip; (Mandibular Prominence)

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The fertilized egg starts dividing

• A ball of cells get accumulated within the zona pellucida and it enlarges and breakthrough the zona liberating the cells to be rearranged in to inner cell mass and outer cell mass.

• The outer cell mass give rise to trophoblastic cells which penetrate the endometrium and anchors the embryo to mother’s uterine wall.

• The inner cell mass forms the embryo blast or formative cells.

• The germ disc is formed during second week, bilaminar germ disc.

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The bilaminar germ disk on 12th day of gestation

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The trilaminar germ disc

• The tall cells will be facing the amniotic cavity and the cuboidal cells will form the roof of the yolk sac cavity during second week of development.

• The gastrulation occurs during the third week of development, the primitive streak is formed.

• The cells migrating from the surface embryoblast after passing through the “pit” acquire the features of mesoderm and make their presence felt between surface ectoderm and endoderm.

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THE GASTRULATION

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Siamese twins are the conjoint twins resulting from a single fertilized egg which has not undergone complete division• If the embryonic disc splits vertically in to two,

and grows further, then two maternal twins will be the result of such development.

• If part of the embryonic disc does not separated out and still it is one then the so called Siamese twins or conjoint twins develops; with two heads/or common thorax/abdomen/or extra limbs/two backs sticks together.

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Twins that are dicephalic parapagus have one trunk and two heads

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Thoracopagus

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These twins share the abdomen regions and organs

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Cephalopagus- they share their heads

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Craniopagus

• Craniopagus: Fused skulls, but separate bodies. These twins can be conjoined at the back of the head, the front of the head, or the side of the head, but not on the face or the base of the skull.

• Cephalopagus: Two faces on opposite sides of a single, conjoined head.

• These twins generally cannot survive due to severe malformations of the brain.

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Archeology and teratology

• In Arabia, the twin brothers Hashim ibn Abd Manaf and 'Abd Shams were born with Hashim's leg attached to his twin brother's head.

• Legend says that their father, Abd Manaf ibn Qusai, separated his conjoined sons with a sword and that some priests believed that the blood that had flown between them signified wars between their progeny (confrontations did occur between Banu al'Abbas and Banu Ummaya ibn 'Abd Shams in the year 750 AH).

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During early periods of gestation if mothers are infected with

cytomegalovirus/mumps/measles• It result in defects in brain development, holes

in their fetal hearts and abnormal malformations.

• Microcephaly

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Fetal alcohol syndrome

• Fetal Alcohol Syndrome (FAS) is a pattern of mental and physical defects which develops in some unborn babies when the mother drinks too much alcohol during pregnancy.

• A baby born with FAS may be seriously handicapped and require a lifetime of special care.

• Some babies with alcohol-related birth defects, including smaller body size, lower birth weight.

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The effect of smoking during pregnancy

• Babies born prematurely, babies born too small, babies die before they can be born at all.

• Cigarette smoke contains more than 4,000 chemicals.

• Nicotine and carbon monoxide work together to reduce your baby's supply of oxygen.

• Nicotine chokes off oxygen by narrowing blood vessels.

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The effect of thalidomide

• The birth defects includes extremely short or missing arms and legs, missing ears (both outside and inside), and deafness.

• There is also a risk of other problems such as heart defects, missing or small eyes, paralysis of the face, kidney abnormalities, gastrointestinal abnormalities, poor growth and mental retardation.

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Thalidomide is a sedative agent

• It is now being used for treatment of several medical conditions including leprosy, cancer, and complications from HIV infection.

• In the late 1950's-1960's the thalidomide was used by pregnant women in their first trimester to treat nausea and vomiting caused by morning sickness.

• It resulted in phocomelia, Amelia and other birth defects.

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The radiation hazards

• Ionizing radiation is the kind of electromagnetic radiation produced by x-ray machines, fluoroscopy, or radiation therapy.

• Most diagnostic procedures expose the embryo to less than 5 rad or 50 mSv.

• This level of radiation exposure will not increase reproductive risks (either birth defects or miscarriage).

• According to published information, the reported dose of radiation to result in an increased incidence of birth defects or miscarriage is above 20 rad or 200 mSv.

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The embryo is very resistant to the malforming effects of x rays during

• The first two weeks post conception or the second two weeks from the last menstrual period.

• The embryo is, however, sensitive to the lethal effects of x rays, although doses much higher than 5 rad or 50 mSv are necessary to cause a miscarriage.

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From the third to the eighth week of pregnancy

• The embryo is in the period of early embryonic development but is not affected with either birth defects, pregnancy loss, or growth retardation unless the exposure is substantially above the 20 rad (200 mSv) exposure.

• From the eighth to the fifteenth week of pregnancy, the embryo or fetus is sensitive to the effects of radiation on the central nervous system.

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8th week of pregnancy

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Beyond the 20th week of pregnancy

• The fetus is completely developed, it has become more resistant to the developmental effects of radiation.

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Patients who were exposed to radiation in Hiroshima and Nagasaki

• After 50 years of studying this population, there has been no demonstrable increase in genetic disease.

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The Hot tubs and saunas can produce NTD

• The type of birth defects that might arise affect the brain and spine.

• These are called neural tube defects (NTD).• Spina bifida is one example of a NTD.

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If a person drives for 2 hours continuously

• Then his testicular temperature will be raised by 2 degrees more and this will effect the process of spermatogenesis.

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The common sources of formaldehyde vapors

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Apart from dissection halls and operation theaters

• Sources of Formaldehyde Gas are common throughout most homes and can be steadily off-gassed from lit cigarettes, particle board storage cabinets, subflooring, carpeting, wallboard, electronics, furniture, ceiling and flooring materials, door casings, insulation, and open stoves or heaters.

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The health effects offormaldehyde

• Birth defects, fetal abnormalities, spontaneous abortions, short term miscarriages, and reduced fertility and other negative pregnancy outcomes.

• It is a carcinogen.• It effects spermatogenesis, sperm count is

reduced and abnormal sperms will be more.

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So teratology has a major role

• In different phases of life, influencing the embryology.

• Every thing under the sun and including the sun the teratogen effects influences the embryology.

• Teratology and embryology are inseparable entity.

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