Neurulation Flashcards
What is the role of the notochord?
Defines primordial longitudinal axis of the embryo= extends from primitive node anterior to prechordal plate
Template for vertebral column= signals for development of axial musculoskeletal and contributes to IV discs
Induces neural plate from ectoderm –> CNS
What is the process of neurulation?
- Sonic hedgehog stimulate ectoderm to form the neural plate
- Neural plate stars to evaginate, neural plates start to approach each other
- The folds round up and from neural tube and the rest of the plate becomes surface ectoderm
- Neural tube closure
Develops frome ectoderm posterior to notochord
During step 1 neural crest cells start to migrate out and away from the tube and act like mesoderm structures
What is the difference between primary and secondary neurulation?
Primary neurulation= development from brain to spinal cord lumbar region
Secondary neurulation= caudal eminence forms around day 20, rounds up and connects to primary neurulation stuructue, finishes at day 42
How is the neural crest formed?
During step 1 of neurulation neural crest cells start to migrate out and away from the tube
What are the derivatives of the neural crest?
Cranial= neurons and ganglia of cranial ganglia, cartilage and bone, connective tissue
Trunk= sensory neurons, Schwann cells, arachnoid and pia mater, melanocytes, thyroid gland, adrenal medulla, parts of heart, eye, teeth
How are the meninges formed?
The meninx primitiva which is mesoderm in origin but has neural crest cells (migrate and mingle) and sclerotome cells
from this the Pachymenix= neural crest, dura mater, mesoderm and the Leptomeniges= arachnoid and pia mater are derived
What happens during the 3rd week of human development?
Gastrulation
What happens during the 4th week of human development?
Neurulation and embryo folding
What is Spinal bifida occulta?
Spinal cord neural tube defect
Caudal closed just not on time, so the neural cord is formed but the neural arches do not fuse
Normally no defects
Tuft of hair from surface ectoderm
What is Meningocele?
Spinal cord neural tube defect
meninges are herniating into cist
May be covered by skin or just a membrane
neural tissue is in correct spot, not vertebral arches
defects possible
What is Meningomyelocele?
Spinal cord neural tube defect
everything herniating out= spinal cord and meninges
will have motor and sensory defects
What is Myelocele?
Spinal cord neural tube defect
caudal end did not fuse at all so spinal cord exposed to the enviroment
What is anencephaly?
Cranial congenital neural tube defect= failure of rostral closure
No closure so basically no brain because from the neural ectoderm
What is Encephalocele?
Cranial congenital neural tube defect= failure of rostral closure
in complete closure so can or cannot have brain tissue
