Embryology I Flashcards
When does the neural tube begin to fold and become a tube?
Day 22
The _________ cavity surrounds the epiblast.
amniotic
The ___________ cavity surrounds the hypoblast.
yolk sac
The ectoderm, endoderm, and mesoderm arise from the ____________.
epiblast
What is immediately deep to the neural tube?
The notochord
How long does the zipper-like closing of the neural tube take?
4 - 6 days
The zipper-like closing of the neural tube starts _________ and then proceeds ___________.
in the middle; caudally and rostrally
The adult spinal cord terminates in a structure called the _________ around the L2 vertebra.
conus medullaris
Describe spinal-nerve naming and how it differs between cervical vertebrae and the other vertebrae.
The cervical vertebrae are named for the vertebra that each passes superior to – so the C1 nerve exits the spinal above the C1 vertebra –while the rest of the vertebrae are name for the vertebra that each exits inferior to –so the T1 nerve exits the spine inferior to the T1 vertebra.
___________ is secreted by the notochord; this gives rise to the dorsoventral patterning in the forebrain. This is called primary neurulation.
Sonic hedgehog
Inferior to the cephalic flexure, dorsal is toward the ___________, while superior to it dorsal is __________.
back; top of the head
“Rostral” means ___________.
toward the nose/frontal cortex
What adult structures develop from the diencephalon?
Thalamus, hypothalamus, and epithalamus
The cerebral cortex develops from the __________.
telencephalon
The mesencephalon gives rise to the __________, while the rhombencephalon gives rise to the ________ and __________; these then give rise to the _________.
midbrain; metencephalon; myelencephalon; pons and cerebellum (metencephalon), and medulla (myelencephalon)
What decides the caudal end of the embryo?
The side of the inner cell mass that enters the uterine wall more deeply
The protein ____________ induces head formation in the epiblast.
nodal
_________ inhibits nodal.
Cerebrus
Secondary neurulation produces the ___________.
conus medullaris and filum terminale
Failure of the neural tube to close at the anterior neuropore will lead to ____________.
anencephaly (failure of the forebrain to develop)
Neural tube defects have been reduced by ______________.
women taking 400 ug of folic acid daily during the first trimester
What two molecules promote forebrain development?
Cerebrus and dickkopf
The seven segments of the rhombencephalon develop different structures due to _____________.
different concentrations of morphogens leading to the activation of different subtypes of Hox genes
Explain the teratogenic relationship between Accutane and retinoic acid.
Retinoic acid is a morphogen – one that participates in the rhombencephalon differentiation process. Accutane mimics retinoic acid and can cause severe birth defects as it alters the normal retinoic acid gradient.
Describe the sequence that the six cortical layers form in.
Sixth (deepest) forms first, then each layer is added on more superficially (5, then 4, then 3, etc.)
BMP-poor zones develop into __________ structures.
midline
A disorder can result in which the neural tube connects to the skin. What is it called?
Myelomeningocele
Wnt signalling is higher in the _________ end of the neural tube.
caudal
Recall that the dorsal root ganglia arise from ___________ cells.
neural crest
Mutations in the _________ gene can lead to holoprosencephaly.
Shh
