LG 5.4 - Embryogenesis Flashcards
What are the definitions of: birth defects? congenital disorder? teratology? teratogen? critical period?
- birth defect: term for a congenital malformation (physical anomaly).
- congenital disorder: a condition existing at birth and often before birth, or that develops during the first month of life, regardless of causation.
- teratology: the study of causes and biological processes leading to abnormal development.
- teratogen: any substance that causes birth defect.
- critical period: time of increased sensitivity.
What is an example of teratology and a teratogen?
- In Europe a drug called Thalomid was given to pregnant mothers to reduce morning sickness.
- At the time people though babies had no connection to their mothers.
- This drug resulted in a limb defect.
- FDA wanted more evidence before supporting the drug and developed the Kefauver-Harris Drug Amendments Act in 1962, which requires manufacturers to prove that drugs are safe and effective before they are marketed.
What can cause birth defects?
- Genetics: mutations in genes or something getting passed from parent to child.
- Environment: intrauterine environment, infections, drugs, diet.
- Unknown- 65% of defects have unknown causes.
- Defects are mostly multifactorial.
What is the difference of calculating weeks of of pregnancy in embryology vs. the clinic?
- In embryology fertilization begins at conception. Embryology is taught using days post-fertilization.
- In the clinic, you do not know when fertilization began so you go back 2 weeks earlier at the beginning of the last menstrual period.
(2) How is sex of the zygote determined?
- By the sex chromosome being carried by the sperm. If X = girl, if Y = boy.
(3) Difference between pluripotent stem cells and multipotent?
- Pluripotent: embryonic stem cells. ability to differentiate into any cell type. Highly clonal geneic: capable of dividing many times without differentiating.
- Multipotent: adult stem cells. Limited to differentiating into different cell types of their tissue of origin.
(3) What are teratomas?
- tumors that arise from pluripotent stem cells that can differentiate into any of the three germ layers or their derivatives. May contain a variety of tissues, including bone, hair, muscle, etc.
(5) What structures form around the outside of the developing embryo to feed it, why might these result in bleeding from mother?
- Trophoblastic lacunae: develop within tropoblast to transport mothers nourishing blood to fetus.
- implantation bleeding: site of implantation has usually healed at this point, but if not the rush of blood to this area can cause bleeding.
(8) What is the structure and function of the placenta?
- An organ that connects the developing being to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother’s blood supply.
(8) What is the structure and function of the umbilical cord?
- Connects the embryo with the placenta.
- Takes blood from the embryo to the placenta and back again.
(8) What combination of tissues forms the placenta?
- Tissues of the uterus and embryo. Mother and fetus part.
(8) Do blood supplies of mother and embryo mix? Why why not? What can cross barrier?
- Do not mix.
- Blood types may not be compatible.
- Mother’s blood pressure might damage embryo.
- Gases, nutrients, some antibodies, etc.
(8) What is placenta previa? What can it result in?
- When the embryo develops at the inferior end of uterus by cervix. Can result in hemorraging.
(8) How are dizygotic twins formed? How do the fetus’ differ?
- Result from two oocytes fertilized by different spermatozoa.
- Totally different genetic constitutions.
- May be same or opposite sex.
(8) How are monozygotic twins formed? How do the fetus’ differ?
- Result from splitting of the zygote at various stages of development.
- Can share sacs depending on where the splitting occurs.
- Can happen prior to implantation, or during blastocyst stage (inner cell mass).
- Will be same sex.
- Same genetic constitution.
