Embryology (complete) Flashcards
how many in 1000 children have distinct anatomical alterations at birth
30
About what percent of birth defects are of known causes
50
What are environmental factors that cause birth defects
maternal disease
infections
mechanical
drugs or chemicals
What is a teratogen
anything that causes a birth defect
What is teratology
the science that seeks to understand causes of birth defects
What are the two factors that influence how likely and how serious a birth defect will be when exposed to a teratogen
- the dose of exposure to the teratogen
2. the period of exposure to the teratogen
What is the leading cause of mental retardation in america
fetal alcohol syndrome
What is thalidomide, and what does it cause
it is an anti-nausea agent that inhibits vessel development and can lead to lack of limb formation
When is the worst time for an embryo to be exposed to teratogens
from 3 - 8 weeks
What are two periods of a pregnancy
embryonic period
fetal period
when is the embryonic period
from conception to 8 weeks
what happens in the embryonic period
a lot, but specifically the formation of all organs
when is the fetal period
from week 9 through term
what happens in the fetal period
the organs that were already formed grow and develop
What are the 5 steps of human development
- pregenesis
- blastogenesis
- organogenesis
- metamorphosis
- phenogenesis
What is pregenesis
developmental pre-conditions in parents that enable successful reproduction. (the creation of the sperm and egg cell that became you)
What are the four parts of pregenesis
- formation and migration of parental primordial germ cells
- differentiation and creation of gonads (testis and ovaries)
- mitosis to increase number of primordial germ cells
- gametogenesis, maturation of gametes (meiosis)
What are primordial germ cells
the cells that will eventually become the sperm and egg cells
From which germ layer do the primordial germ cells come from
the ectoderm
What is the path the primordial germ cells take starting with the ectoderm and ending in the gonads
- they leave the ectoderm right away and go into the yolk sac
- they re-enter the embryo at 4 weeks and enter the gonads
What is a teratoma
when germ cells migrate to locations other than the gonads and begin to proliferate rapidly. they create a large tumor
can Teratomas have traces back to all three germ cells
yes
What is meiosis
a special form a cell division that leads to the formation of 4 haploid cells.
what are haploid cells
cells with half of the DNA of a regular (diploid) cell