Neurulation & Embryonic Folding Flashcards
neurulation
formation of the neural tube
process of neurulation
notochord induces ectoderm to give rise to a midline depression called the neural groove and two lateral elevations called the neural folds. neural folds grow larger and eventually fuse with each other to form the neural tube
when is neurulation completed by
end of 4th week
what does the neural tube develop into
the central nervous system (brain and spinal cord, retina)
neural crest cells
cells along edges of neural folds segregate themselves from the neural folds
lie between ectoderm and neural tube
migrate to various parts of the body and develop into various structures
defects in migration can lead to anomalies
neural crest derivatives
muscles of face and scalp
bones of the skull
spinal ganglia
meninges
neurolemmal sheaths
pigment cells/melanocytes
supra renal medulla
parts of intra-embryonic mesoderm
paraxial mesoderm
intermediate mesoderm
lateral mesoderm
somite formation
paraxial mesoderm divides into paired cuboidal bodies
on each side of neural tube
4th and 5th week
42-44 pairs at end of 5th week
each somite divides into
sclerotome: cartilage and bone of the vertebral
myotome: muscles
dermatome: dermis and subcutaneous tissue
intraembryonic coelom
space that develops in the lateral mesoderm
horse shoe shaped
in second month it gives rise to 3 cavities of the body (pericardial cavity, pleural cavity, peritoneal cavity)
surfaces of the placenta
maternal surface: rough, 15-30 cotyledons
fetal surface: smooth, covered by chorionic plate, covered by amniotic membrane
functions of placenta
provides:
protection, nutrition, respiration, excretion
hormone production: HCG, placental oestrogen, prostaglandins
umbilical cord
formed by 5th week of development
comes from connecting stalk
connection between the placenta and the embryo
2 veins & 1 artery
~50 cm
