Embryology 2 Flashcards
What are the 3 roles of the notochord
- establishes the longitudinal axis of the embryo and gives it some rigidity
- provides signals for the development of axial MSK structures and the CNS
- contributes to the intervertebral discs
mesenchymal cells dive into the primitive pit and migrate cephalad, they form a cord called what?
notochordal process
the notochordal process develops a lumen known as the ?
notochordal canal
after the notochordal process approaches the prechordal plate, the floor of the process “fuses” with the ?. The notochordal process is now the ?
endoderm
notochordal plate
notochordal plate -> notochord transition starts
cranially and progresses caudally
the notochord induce the overlying ectoderm to develop into the ?
neural plate
the prechordal plate develops into the ?
oropharyngeal membrane
the oropharyngeal membrane has how many layer membrane?
ectoderm and endoderm, no mesoderm
What forms caudal to the primitive streak
cloacal membrane
how many layers are in the cloacal membrane?
two layers - ectoderm and endoderm, no mesoderm
what is the future site of the anus
cloacal membrane
what is allantois and what does it do?
small, vascularized diverticulum from the caudal wall of umbilical vesicle, extending into the connecting stalk
- functions in early blood formation and bladder develop, blood vessels become umbilical arteries
notochord induces overlying ectoderm to form the ?
neural plate also known as neuroectoderm
on day 18, the neural plate invaginates to form ?
the neural groove - neural folds are found on either side of the groove
the neural folds eventually fuse together, and form the ?
neural tube
what is neurulation
the process by which the neural tube is formed
True or False: during the 3rd week, intraembryonic mesoderm proliferates to form a thick column of mesoderm on either side of the notochord
true
what is paraxial mesoderm
right beside the notochord
where is the intermediate mesoderm
just lateral to the paraxial mesoderm
where is the lateral mesoderm
lateral to the intermediate mesoderm
what are somites?
cuboidal masses of mesoderm on either side of the notochord, visible along the dorso-lateral surface of the embryo on each side of the neural tube, formed from the paraxial mesoderm
during the 3rd week mesenchymal cells migrate anteriorly, lateral to the notochordal process to eventually form what?
cardiogenic mesoderm
the primordium of the intraembryonic coelom (embryonic body cavity) appears where?
isolated spaces in the lateral mesoderm and cardiogenic mesoderm
intra-embryonic coelom divides the lateral mesoderm into 2 layers which are?
- somatic or parietal layer of lateral mesoderm located beneath the ectodermal epithelium and continuous with the extraembryonic mesoderm
- splanchnic or visceral layer of lateral mesoderm next to the endoderm and continuous with the extraembryonic mesoderm covering the umbilical vesicle
3 general structures in the region of the lateral mesoderm:
- somatopleure
- splanchnoplleaure
- intraembryonic coelom in between the somatopleure and splanchnopleure
what is the somatopleure and where is it?
the somatic mesoderm and the overlying ectoderm, forms the body wall
what is the splanchnopleure and where is it?
the splanchnnic mesoderm and the underlying intraembryonic endoderm, forms the embryonic gut
during the 2nd month, the intraembryonic coelom develops into 3 main body cavities which are:
- pericardial cavity
- pleural cavity
- peritoneal cavity
what is embryonic folding
the process by which a relatively “flat” embryonic disk becomes more and more cylindrical in shape
folding occurs in 2 general planes which are?
the median plane and horizontal plane
describe embryonic folding in the median plane
anterior and posterior ends of the embryo move ventrally
median plane is also known as?
cranial-caudal folding
describe embryonic folding in the horizontal plane
the lateral edges of the embryonic disk move ventrally
the horizontal plane is also known as ?
lateral folding
what is the primordium of the mouth
stomodeum
the position of the heart changes due to what?
the head fold
lateral folding is caused by the rapidly growing what?
spinal cord and somites
what are the 3 germ layers?
- ectoderm
- mesoderm
- endoderm
the neural plate can been seen at what day?
day 19
what line the central canal of the spinal cord?
ependymal cells
the alar and basal plates of the developing spinal cord are separated by a groove called?
the sulcus limitans
cell bodies in the alar plates form what?
the dorsal gray horns
cell bodies in the basal plates form what?
ventral and lateral gray horns
the unipolar neurons in the spinal ganglia (dorsal root ganglia) are derived from what?
neural crest cells
fusion of the neural folds in the cranial region and closure of the rostral neuropore form 3 primary brain vesicles:
- forebrain (prosencephalon)
- midbrain (mesencephalon)
- hindbrain (rhombencephalon)
during week 5, the prosencephalon partially divides into 2 secondary brain vesicles which are?
telencephalon and diencephalon
by week 5, the rhombencephalon also partially divides into?
metencephalon and myelencephalon
