Week 3- Formation of Germ Layers Flashcards
which embryonic week is characterized by rapid development from the embryonic disc to the actual embryo?
week 3 of development
what three main things happen surfing week 3 of development
- primitive streak appears
- notochord develops
- three germ layers separate
what are some frequent pregnancy symptoms
- nausea
- vomiting
what does not rule out pregnancy because it could be caused by implantation bleeding?
vaginal bleeding
what results from the leakage of blood into the uterine cavity from disrupted lacunar networks in the implanted blastocyst?
implantation bleeding
what means the formation of the three germ layers
grastrualtion
what are the three different germ layers
ectoderm
mesoderm
endoderm
during grastrulation what happens to the bilaminar dic
it becomes a trilaminar dic
what is morphogenesis?
the development of the embryos’s body form
when is morphogenesis really significant?
during week 3 of development
what are the 3 signaling proteins that play an essential role in grastualtin?
- BMP’s ( Bone Morphogenetic Proteins)
- FGFs (Fibroblast Growth Factors)
- Wnts
which germ layer gives rise to
- epidermis
- PNS
- eye
- inner ear
- neural crest cells
ectoderm
which germ layer is the source of
- epithelial linings of respiratory and digestive tracts
- liver
- pancreas
endoderm
which germ layer give rise to
- skeletal system
- connective tissue
- dermis
- blood cells
- circulatory system
mesoderm
what appears caudally in the median plane of the dorsal aspect of the embryonic disc
the primitive streak
the cranial end of the primitive streak proliferates to form what
primitive node
what happens to primitive streak overtime
it diminishes in relative size and becomes an insignificant structre
when does the primitive streak usually disappear?
week 4
what is sacroccygela teratoma?
this is when there is a remnant of the primitive streak and a tumor that contains tissues from all three germ layers is present (hair and teeth)
which infants are most affected by sacroccygeal teratoma (80%)
females
you can see a sacrococcygeal teratoma with what device?
sonograph
the notochordal process is formed by cells that migrate through the streak when?
day 16 of embryonic development
what are considered to be benign and malignant tumors that may form from vestigial remnants of notochrdal tissues
chordomas
1/3 of chordomas occur where
at the base of the cranium and extend to the nasopharynx
at what rate dies a chroma grow
slowly
at day 16 what appears as a small sausage that is outpouching from the caudal wall of the umbilical vesicle that extends to the connecting stalk?
allantois
the proximal part of the alantois that remains through development is called the
urachus
what extends from the bladder to the umbilical region
urachus
what is the urachus represented by in adults
the median umbilical ligament
what are known as the remnants of the extraembryonic potion of the allantois, and are usually found between the fetal umbilical vessels and can be detected by ultrasound
allantoic cyst
allantoic cysts are generally asymptomatic till when
childhood or adolescence because thats when they start running around a lot more
what is the process involved in the formation of the neural plate and neural folds and closure of the folds to form the neural tube
neurulation
durring neuraltion what may the embryo be referred as?
a nerurula
the notochord induces the embryonic ectoderm to do what adjacent to the midline
it induces it to thicken and form elongated plate of epithelial cells called the neural plate
the ectoderm of the neural plate (neuroectoderm) gives rise to what
CNS
the neural folds are prominent where
at the cranial end of the embryo
the cranial neural folds indicate what kind of development
brain development
when do the neural folds move together?
by the end of week 3
when the neural folds move together at the end of week 3 the neural plate turns into the…?
nerual tube
what ganglia of cranial nerve cells derive in part from the mesoderm
CN V, CN VII, CN IX, and CN X
the disturbance of neurulation may cause some abnormalities where
in the brain and spinal cord
meroencephaly
partial absence of the brain
3 neural tube abnormalities
- ancephaly
- spina bifida
- meroencephaly
at the end of the 3rd week the paraxial mesoderm differentiates and divides into paired cuboidal bodies called?
somites
by the end of the 5th week how many somites are there
42-44 pairs
somites are the primordial for what
the skeletal system
somites can help determine what
embryonic age (at 4- 5 weeks old)
what does the somatic mesoderm and embryonic ectoderm form?
somatopleure, or embryonic body wall
the splanchnic mesoderm and underlying embryonic endoderm for the embryonic gut also known as?
splanchopleure
when will the intraembryonic coelm divide
by the end of the second month in three cavities
what are the 3 cavities of the intraembryonic coelom
- pericardial cavity
- pleural cavities
- peritoneal cavity
vasculogenesis and angiogenesis takes place when
at the beginning of week 3
what is the development of blood vessels called?
angiogensesis
why does the cardiovascular system form so early
because there is an urgent need for blood vessels to bring oxygen
what is the early embryo called when the nerual tube is developing (third to fourth week)?
Neurula
