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)
What is a totipotent cell? give an example
a cell that can differentiate into all cell types of the body AND PLACENTAL STRUCTURES
ex: zygote and blastomere
What is a pluripotent cell? give an example
a cell that is able to differentiate into all cell types of the body (NOT placental structures though!)
- derived from totipotent cell
ex: embryonic stem cell
what is a multipotent cell? give an example
a cell that is able to differentiate into a limited number of cells;
ex: a homepoitic cell = multipotent but can only differentiate in any blood cell (no other tissue)
Explain the process of morphogenesis
establishment of form and structure; cells become organized into tissues and organs; organs are arranged in specific ways into systems
What is cell growth?
cell development and REGULATED cell division (mitosis)
What is the process of reproduction?
process by which new individual organism is produced;
sperm and egg are specialized in this function
What percentage of births have major congenital anomalies?
4-6% (half recognized at birth; half by age 5)
what percentage of births have minor congenital anomalies?
15%
what is the leading cause of infancy death?
birth defects; 21%
