Organogenetic Period Flashcards
What is the organogenetic period?
all major internal/external structures are established during this period
What happens during weeks 4-8 of embryonic development?
the organogenetic period
Which systems become functional first in the embryonic period?
all major systems begin developing by end of this period
- function is minimal in all but cardiovascular system
What will the fetus look like at the end of embryonic period?
human appearance
What are teratogens?
agent that produces or increases the risk of developing a congenital anomaly
Why is the risk of congenital abnormalities high during the embryonic period?
because all major internal/external structures and organ systems are developing during this period in time
When is the fetal period?
weeks 9 - birth
What is occurring in the fetal period?
differential growth of tissues and organs and systems
What is the susceptibility to teratogens during the fetal period?
less susceptible
How do the body proportions change in the fetal period?
head growths slow proportionally as body growth increases
prior to 22 weeks or less than 500g, what is the fetal viability?
usually non-viable
Between 26-28 weeks and more than 1500g, what is the fetal viability?
may survive but often with complications
After 35 weeks and more than 2500g, what is the fetal viability?
usually survive
Development is predicated on what 3 interrelated phases of activity?
- growth
- morphogenesis
- differentiation
What is growth predicated on?
results from cell division and production of extracellular products
What is morphogenesis?
develop the structure of the organs and/or organ systems
What is morphogenesis predicated on?
requires specific sequences of events and cellular interactions
What is differentiation?
complete formation of tissues and organs capable of performing specialized functions
Why is the cardiovascular system the first to develop?
necessary to meet nutrition and oxygen requirements of growing embryo
When does the cardiovascular system first appear?
primordial heart and blood vessels appear in week 3
