General embryology

EMBYRIOLOGY

الاثنين 8/12/2013
Lec.4
أ.د.عبد الجبار الحبيطي

Infectious Diseases includes

1-Rubella (German Measles)
2-Cytomegalovirus
3-Syphylis
4-Toxoplasmosis

The effect of Rubella on the growing fetus are the following features:

a-Congenital cataract
b-Congenital deafness
c-Mental retardation
d-Congenital heart defects
e-Occasionally defect in the enemal layer of teeth.


The effect depend on the time of exposure of the pregnant mother to Teratogenic agent …in cases of Rubella virus if the mother catch it at about 6 th weeks of pregnancy,then at birth we can see most of the features of Rubella mainly Congenital Cataract,but if it get it at 8-9 weeks of development ,there will be Congenital deafness but no effect on the eyes ( no congenital cataract)

Cytomegalovirus infection Toxoplasmosis

1-Complete loss of vision 1-Partial loss of vision
2-Intracranial calcification 2-Intracranial calcification
3-Microcephally 3-Hydrocephally
4-Delayed and severe degree of 4-Mental mental Mental retardation
5-Hepatosplenomegally 5- Microphthalmous other
Kerniecterus and severe mental occular defects
Retardation due to jaundice.

Syphilis leads to following features in new born baby:

1-Cleft lip and palate ( very high incidence )
2-Spina bifida

Radiations and Antotoxic Drugs

Has a direct effect on developing fetus as there is a strong association between exposure to radiation and the appearance of congenital malformations and the same can happen on taking anti-toxic drugs.An example for the effect of adiation is what has happened in Japan during 2nd world war in 1945 as a resut of atomic bombs thrown on Hiroshima and Nagazaki .All females in these 2 cities remained alife after bombing and became pregnant later on a survey was done and showed that 28% were aborted ,25% has intrauterine death of fetuses,25% of babies born alive were died during the first year of age and the remaining showed chromosomal defects and mutations.

FETAL MEMBRANES IN TWINS

A-Dizygotic (Fraternal )Twins
It occurs in 7-11 per thousand birth and results from the fertilization of 2 shedded oocytes by different spermatozoa and each of the Twins has:
1-Different genetic constitution.
2-Has no more resemblance than any other brother or sisters.
3-May or may not be of different sex.
4-Each zygot implants individually in the uterus and usually each develops its own placenta,amnion & chorionic cavity
5-Occasionally each one processes red blood cells of 2 different types ( Erythrocyte Mosaicism ).


B-Monozygotic (Identical ) Twins
Occurs in 3-4 per thousand birth and they have strong resemblance in
1-Their blood group
2-Finger print
3-Sex
4-External appearance ( Eye & Hair color)

If separation at 2 cell stage then each one has its own

placenta,amnion & chorion
If splitting at early blastocyst thenthe 2 has common placenta&chorion but each has its own amniotic cavity
If splitting at bilaminar disc ( before the appearance of primitive streak),then they have common placenta,chorion & amniotic cavity.