Terminology and Basics Flashcards
when does the fertilization age start? how long is the pregnancy?
dates pregnancy from the time of fertilization (14 days after the last menstrual period); 38 weeks
when does the menstrual age start? how long is the pregnancy?
dates pregnancy from the last menstrual period (LMP); 40 weeks
what are the three ways to determine the embryo/fetus age?
- measure the gestational sac *chorionic cavity) diameter
- Measure the crown rump length (from top of head to bottom of buttock) and compare to a standardized chart
- measure the size of the head
What is the length of the embryonic period?
from the time of fertilization to 8 weeks
what are the two divisions of the embryonic period?
- Early development (0-3 wks)
2. Embryonic organogenesis (4-8 wks)
What are the stages of the fertilization age?
- embryonic period
2. Fetal period
What does the early development sub-period of the embryonic period entail?
early embryogeneisis; 0-3 weeks after fertilization (cleavage, gastrulation)
what does the embryonic organogenesis sub-period of the embryonic period entail?
neuralation and embryo folding
What is a teratogen?
a factor (a drug or environmental toxicant) that causes a birth defects
During which weeks of embryo development is a teratogen most dangerous? when is it least? why?
From weeks 0-3 exposure to a teratogen wouldn’t cause deform in the embryo because it would just cause embryonic death;
From weeks 4-8 (organogenosis): exposure to a teratogen causes a HIGH risk of major congenital anomaly (especially weeks 4-6)
From weeks 9-38 (Fetal period): exposure to a teratogen causes functional defects and minor anomalies
When is the fetal period? what features are unique?
- from 9-38 weeks after fertilization
- organ systems mature and there is RAPID GROWTH
- environmental factors typically cause only minor defects
What is induction with relation to embryology?
a process by which one tissue or group of cells (inducer) produces a signal that changes the fate of an adjacent tissue or set of cell
how many cells are required for induction?
2 cells; one that does the inducing, and one that gets induced
Describe the process of differentiation (what is it):
process by which a LESS specialized cell becomes MORE specialize;
generates cell diversity
how many cells are need for differentiation?
ONE CELL; but gives rise to many other cell types (increases cell diversity)
