Basic Embryology Exam Review Info Flashcards
What are the 3 germ layers?
Ectoderm, Mesoderm, and Endoderm
what does the ectoderm form?
forms the:
- nervous system (brain and SC)
- epidermis
- hair
- nails
- glands
what does the mesoderm develop into?
- muscle (skeletal, cardiac, and smooth)
- bone
- circulatory system
- connective tissue (dermis of the skin)
- Reproductive system
what does the endoderm form?
- digestive tract
- respiratory system
- parts of the endocrine system
- liver
what happens to the egg in ovulation?
egg is released into peritoneal cavity and enters the fallopian tube
what is and where does fertilization occur?
- occurs in the fallopin tube
- it is when the maternal and paternal genetic material combine and form a zygote
what is a morula?
a cluster of cells that is formed when the zygote divides as it travels through the fallopin tube
how many blastomeres make up a morula?
12-16 at about 72 hours
when does a morula become a blastocyst?
around day 4
when does a blastocyst implant in the uterus?
around day 7
blastocyst stage facts…
- hanging out in the uterus for about 3 days
- two cell types (inner cell mass and trophoblast)
- implantation on about day 7
what are the two cell types in a blastocyst?
- inner cell mass: forms the embryo
- trophoblast: forms the placenta (surrounds the cavity)
trophoblast _____ uterine wall?
erodes
how do monozygotic (identical) twins occur?
inner cell mass of a single blastocyst splits into two
Week 2: what is in each, explain?
- bilaminar embryonic disc
- 2 fluid filled sacs
- bilaminar embryonic disc
epiblast - extend around amniotic cavity
hypoblast - extend into blastocyst - 2 fluid filled sacs
epiblast -> amniotic sac -> protection
hypoblast -> yolk sac -> mnutrients and blood flow, will serve as blood cells and germ cells -> until week 4
week 3:
what happens with the layers?
- bilaminar to trilaminar disc
- three primary germ layers develop all the body tissues
- formation of the 3 germ layers
what takes place in the formation of the 3 germ layers?
- primitive streak on dorsal surface or epiblast
- gastrulation
gastrulation?
invagination of epiblast cells
week 3: days 14-15
endoderm replace hypoblast
ectoderm - epiblast cells remaining on surface
week 3: day 16
mesoderm (a new third layer) form between
Notochord?
- days 16-18
- primitive node epiblast cells invaginate and migrate anteriorly
- rod defining the body axis is formed
- future site of the vertebral column
divisions of the mesodermal lateral plate
- forms serous cavities of the ventral body
- somatic (parietal) mesoderm cells -> connected to ectoderm
- splanchinic (visceral) mesoderm cells -> connected to endoderm
different somatic (parietal) mesoderm cells?
peritoneal
pericardial
pleural
what does the serous membrane cells surround?
each organ
closure of neural tube is when?
end of week 4
mesoderm begins to differentiate when?
week 3
when does the heart start pumping?
day 29
4 weeks
one month
by 8 weeks:
all major organs are placed in at least a rudimentary form; this is why drugs early in pregnancy are so important to avoid - many cause birth defects
embryo is a little over 1 inch long
embryonic period
first 8 weeks
all major organs are formed during this time
crucial because exposure to teratogens can result in significant birth defects
fetal period
weeks 9-38
organs grow and become more complex
body develops into more recognizable human form
neurlation
neural tube begins to form around day 16-18 and closes by the end of week 4
vital for central nervous system development
importance of folic acid
essential during early pregnancy to prevent neural tube defects (spina bifida) during the first 4 weeks
