Neurulation & Limb development Flashcards
Primitive node
- appears at the cranial end of the primitive streak
- cells have single, solitary, motile cilia
- fluid contains vesicles with sonic hedgehog protein (Ssh)
- asymmetric division - caused by fluid movement and release of Ssh
Notochord
- cells of primitive node delaminate and migrate along primitive streak
- plays an important role in the development of nervous system
Ectoderm forms into
skin, nervous system
Mesoderm forms into
bones, muscles, connective tissue
Endoderm forms into
gut system (liver, pancreas, etc)
3 types of congenital anomalies
- failure of migration (if epiblast cells fail to migrate, cannot establish a trilaminar embryo)
- failure of induction (the notochord has to induce the overlying ectoderm to become nervous tissue)
- failure of fusion (where two tissues have to fuse together) ex. ventral body wall defect
3 types of mesoderm
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
paraxial mesoderm gives rise to
somites
intermediate mesoderm gives rise to
urinary and reproductive systems
lateral plate mesoderm gives rise to
limb bones and connective tissue
what does lateral folding of embryo do?
- forms the gut tube
- creates the body cavities
- brings the embryo “into” the amniotic cavity
what does cranial folding of embryo do?
- driven by the developing forebrain
- brings the buccopharyngeal membrane form the dorsal surface to the ventral surface
- bring the developing heart into the thorax
what does caudal folding of embryo do?
- brings the cloacal membrane from the dorsal surface to the ventral surface
- establishes the openings for urinary system, digestive system and reproductive system (all derived from cloacal membrane)
how is neural plate formed?
notochord induces the overlying ectoderm to form neural plate
how is neural tube formed?
lateral sides of the neural fold will eventually meet and fuse on the dorsal midline, in the thoracic regoin of the embryo
fusion of ectoderm on the dorsal surface to cover the neural tube creates
cranial neuropore and caudal neuropore
neural tube defects if cranial neuropore doesn’t close
anencephaly (no brain)
neural tube defects if caudal neuropore doesn’t close
spina bifida
- spina bifida occulta
- meningocele
- meningomyelocele
- rachischisis
spina bifida occulta
gap in the spinous process and a tuft of hair
spinus bifida with meningocele
bigger gap in spinous process that could result in pocket filled with spinal fluid
spinus bifida with meningomyelocele
bigger gap in spinous process - nervous tissue protruding in that gap/pocket
- spinal cord is in the outpocketing of the meninges
rachischisis
when the neural tube completely fails to fuse, mesoderm doesn’t have the opportunity to migrate, ectoderm doesn’t fuse
(neural defects here cannot be fixed since they are in the lumbar region)
region where spinal cord ends
L1 or L3 (in adults)
position of end of spinal cord changes with age
sacral foramen
hole in sacrum which is a good access point for lumbar puncture in kids
