Embryology Introduction (Exam 1) Flashcards
What are the three main developmental stages of an embryo
early development
embryonic
fetal
When does the early developmental stage occur
day 0-2 weeks
When does the embryonic period occr
3-8 weeks
When does the fetal period occur
9 weeks- birth (38 weeks)
What stage of development is an embryo at highest risk of malformation
embryonic
What typically occurs to malformations that occur during the early developmental period
results in spontaneous abortion
prevents implantation and will not be viable
What events will occur during early development
- fertilization
- implantation
- proliferation
- formation of trilaminar embryo
- formation of placenta
- determination of body axes
What is the trilaminar embryo
When the embryo has formed its 3 primary layers from which all cells will divide from
What stage of development is this seen in
early stage of development
During which stage of development will all organs and body parts form
embryonic stage
What makes the embryonic stage at increased risk for injury
due to a lot of organ formation and cell division there is increased risk for injury
How will an embryo enter the embryonic period
as a trilaminar embryo
What occurs during the fetal period of development
- finalization and maturation of organ development
- increase in length and weight
How does weight development in a fetus
not uniform, greatest prior to birth
How does length development in a fetus occur
uniformly
What organs are susceptible to injury during the fetal period
brain ears teeth palate external genitalia eyes
What is NOT included in external genitalia
gonads, these develop inside then come down closer to birth
What is a congenital anomaly
abnormalities that are present at birth
What determines what undifferentiated cells will become
cell signaling
What is induction
two tissues communicating with each other, one will induce the other to perform an action
How does induction occur between notocord and ectoderm
notochord causes the ectoderm to thicken and form the neural plate, where the neural tube will ultimately form from
What differentiates the different levels of the spinal chord
gene expression
What are the stages of the cell cycle
G1 S G2 M G0 GTD
What occurs during G1 phase
gap phase
DNA damage checkpoint prior to S phase
What occurs during S Phase
Dna Synthesis
What occurs during G2 phase
Gap phase 2, DNA checkpoint, unreplicated
What is the M phase
Mitosis
What is G0 phase
cells that are not actively dividing
What is produced by mitosis and what will the products contain
2 daughter cells that have diploid genomes with identical DNA as the parent cell
What is the DNA content of a diploid cell
46 chromosomes
-22 pairs of autosomal chromosomes and 1 pair of sex chromosomes
What are the different terms of ploidy
Haploid
Diploid
What is Haploid
cell has just one copy of maternal or paternal strands of DNA
- just one strand of each chromosome
What is Diploid
cell has both maternal and paternal strands
-2 chromosomes
What is produced from meiosis
4 haploid cells that are genetically unique
What are the steps of meiosis
Prophase I Metaphase I Telophase I Anaphase I Metaphase II Telophase II Anaphase II
What occurs during Prophase I
the doubled DNA condenses into chromosomes, and crossing over occurs
What is the process of crossing over called
pachytene
What occurs during Metaphase I
chromosomes align at random in the center, mitotic spindle forms
What occurs during Anaphase 1
The chromosomes are pulled apart to opposite poles
What occurs during Telophase I produce
2 daughter cells that are haploid with unique genomes
What occurs during Metaphase II
the chromosomes again line up inside the cells
What occurs during Anaphase II
the chromosomes are pulled apart
What is the results of Telophase II
4 haploid daughter cells with unique genomes
What does meiosis result in males
4 spermatids
What does meiosis result in females
one ovum and three polar bodies
Why do polar bodies occur
during division, the ovum gets majority of the cytoplasm
What are the 4 clinically significant types of congenital anomalis:
malformations
dysplasia
deformation
disruptions
What are malformations
occur during organogenesis; results in abnormal structure
There can be “deleterious” malformations called what
anatomical variations
What are disruptions
result from external influences that cause alterations of completely formed structures or organs
What are deformations
abnormal structure resulting from mechanical forces
What is dysplasia
abnormal organization of cells into tissue
What is an example of anatomical variation
three headed biceps
What is an example of disruptions
strangulation by an amniotic band
What is an example of deformation
club feet
What is an example of dysplasia
sacrococcygeal teratoma
What are the three main causes of congenital anomalies
Genetics
Environmental factors
Unknown/Multifactorial
How much does genetics contribute to congenital anomalies
30%
How much does environmental factors contribute to congenital anomalies
15%
How much does unknown/multifactorial factors contribute to congenital anomalies
55%
In North America, how many infant deaths are attributed to congenital malformations
20%
What is agenesis
absence of an organ
What is aplasia
cells to form an organ never formed
What is association
anomalies occurring together without a determined cause
What is atresia
absence of an opening or lumen
What is hyperplasia
overgrowth of an organ
What is hypoplasia
underdevelopment of an organ
What is syndrome
a group of anomalies, occurring together with a common cause
What is teratogen
substance affecting migration, proliferation, or interaction of cells; results in congenital anomalies
What cells is meiosis limited to
gamete forming cells
What are the two significant stages of meiosis I
Pachytene
Metaphase
What occurs during Pachytene
crossing over event that results in unique genetic combinations
What occurs during Metaphase I
maternal and paternal chromosomes align randomly
