2) Embryology and Teratology (Part I) Flashcards Preview

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Flashcards in 2) Embryology and Teratology (Part I) Deck (105)
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What is teratogenesis?

The production of congenital birth defects in an embryo or fetus


What are malfunctions?

Non-reversible morphological defects present at birth


What are the three types of malfunctions?

- External malfunctions (e.g. cleft palate)
- Internal malfunctions (e.g. malfunction in an organ)
- Microscopically visible malfunction


What are congenital anomalies?

Present at birth


How many types of congenital anomalies are there? What can they range from?

- 200 types
- Range from physical abnormalities to fatality


Birth defects are present in what percentage of live births?



What are deaths to birth defects primarily due to?

Structural and functional defects in vital organs


Structural and functional defects in which vital organs are particularly susceptible to cause death?

- Respiratory system
- Heart


What is the leading cause of infant death in North America?

Birth defects


What are the three reasons that explain why birth defects are the leading cause of infant death in North America?

1) Improvements in obstetrical care
2) Increased medications and social drug use
3) Contribution of environmental contaminants to teratogenesis


How does the incidence of birth defects vary at two years old? Why?

- At two years old, the incidence increases from 4 to 6%
- Due to the discovery of internal organ defects, which may have been symptomless at birth


Birth defects account for more than ___ of all deaths in infants below a year old, and ___ of all deaths in children above 15 years old.

- 1/3
- 1/4


Around 20 to 25% of the causes of birth defects are due to what? How are they identified?

- Genetic causes and chromosomal aberrations
- Identified by a constellation of characteristics of defects that are present together


Which factors play a role in the development of birth defects, apart from genetic and chromosomal aberrations?

- Metabolic (maternal illnesses)
- Radiation
- Infection (maternal illnesses)
- Exposure to drugs or chemicals


What is the susceptibility of teratogenesis heavily influenced by?

The genetics of the mother and infant, as well as environmental factors


What percentage of human pregnancies result in a healthy, normal infant?

Less than 50%


What do anomalies occurring during the early stages of embryogenesis lead to?

An early miscarriage


What three outcomes may the formation of a zygote lead to?

1) Healthy pregnancy that comes to term
2) Pregnancy that comes to term with the formation of anomalies
3) Pregnancy that does not come to term


What is the largest contributor to an unsuccessful pregnancy?

Post-implantation losses


What are post-implantation losses?

If the uterus is not ready to receive the zygote, then the fertilized egg is shed along with uterine tissue during the following menstrual cycle


What occurs during the conception period of reproduction?

1) Conception is the formation of a zygote from the union of the ovum and sperm
2) Implantation of the zygote into the uterine wall


What occurs during organogenesis?

The division and differentiation of the ovum to form tissues and organs


When does organogenesis occur?

Weeks 3 to 8 during pregnancy


What is the teratogenic period?

The most susceptible period to birth defects


When is the teratogenic period?

17 to 57 days post-fertilization


When does the neural tube close?

Within 28 days of gestation, when most women do not know they are pregnant yet


What is necessary for women to be CAPABLE of becoming pregnant, and avoiding a neural tube defect?

Adequate nutrition, specifically folate, PRIOR to conception


For all women, there is a __-day period following ovulation.



What is the period of maximal cell division and differentiation? What is it also referred to as?

- The organogenic period
- The critical period of growth


What should occur by the end of the organogenic period?

The development of the major fetal structures should be completed