Neurulation and Somitogenesis Flashcards
What is neurulation?
The formation of the vertebrate nervous system in embryos
How does the notochord develop?
Some mesodermal cells migrate cranially in the midline of the mesodermal layer forming the rod-like notochordal process
What is the neuroectoderm?
Cells derived from the ectoderm within the nervous system
What does the notochord arise from?
Mesoderm
What does the neural tube arise from?
Ectoderm
How does the neural tube form?
The neural plate folds in on itself to form the neural tube which later differentiates into the spinal cord and brain.
Describe the first step in the process of neurulation
- Neuroectodermal tissues differentiate from the ectoderm and thicken into the neural plate, The neural plate border separate the ectoderm from the neural plate
Describe the second step in the process of neurulation?
The neural plate bends dorsally, with the two ends eventually joining at the neural plate borders, which are now referred to as the neural crest.
Describe the third step of neurulation?
The closure of the neural tube disconnects the neural crest from the epidermis. Neural crest cells differentiate to form most of the peripheral nervous system
Describe the fourth step of neurulation?
The notochord degenerates and only persists as the nucleus pulpous of the intervertebral discs. Other mesoderm cells differentiate into the somites, the precursors of the axial skeleton and skeletal muscle
What are somites?
Paired cubodial bodies divide from the differentiation of the paraxial mesoderm
What do somites differentiate to form?
Cartilage of the axial skeleton
Muscles of the rib cage, limbs and back
Cells that contribute to the connective tissue of the dermis
What are the specific regions of the somite?
Sclerotome (bone)
Myotome (muscle)
Dermatome (connective tissue)
What are neural crest cells?
Multipotent neural crest cells migrate widely in embryo and give rise to many nervous structures
What happens to the nueral tube?
Neural tube becomes narrower and longer
Accompanied by lateral folding of the neural plate
Fusion of the neural folds
Separation of the nueral tube from the overlying ectodermal sheet
What is the adult derivative of the notochord?
Notochord persists in adulthood as the nucleus pulpous of intervertebral discs
What is the adult derivative of the notochord?
Notochord persists in adulthood as the nucleus pulpous of intervertebral discs
What is the ependymal layer/
Stem cell for all neurons
What does the ependymal layer divide and give rise to?
Mantle layer and marginal layer
What is in the mantle layer?
Contains cell bodies of motor neuron
What is in the marginal layer?
Contains axons of motor neurons
What is the mantle layer regionally divided into?
Alar plate - sensory- receives axons from the DRG
Basilar plate- contains cell bodies of motor neurons
What are the three primary brain vesicles?
Prosencephalon
Mesencephalon
Rhombencephalon
What are the secondary brain vesicles from the prosencephelon?
Telencephalon
Diencephalon
What is the secondary brain vesicle formed from the mesencephalon?
there is none- it remains as the mesencephalon
What secondary brain vesicles are derived from the rhombencephalon
Metencephalon
Myelencephalon
What adult brain structures does the telencephalon form/
Cerebrum
Cerebral hemispheres
What adult brain structures does the diencephalon form?
thalmus
hypothalmus
epithalmus
retina
What adult brain structures does the mesencephalon form?
Brain stem: midbrain
What adult brain structure does the metencephalon form/
Brain stem: pons
and cerebellum
What type of brain structure does the myelencephalon form?
Brain stem: medulla obolngata
What are the most common forms of congenital abnormalities and what happens?
Neural tube defects and result from a teratongenic drug affecting the neuroectoderm- consequently there is a failure of the neural folds to fuse and form the neural tube
What is craniorachischisis?
Completely open brain and spinal cord
What is anencephaly?
Open brain and lack of skull vault
What is Encephalocele?
Herniation of the meninges
What is iniencephaly?
Occipital skull and spine defects with extreme retroflexion of the head
What is spina bifida occulta?
Closed asympomatic NTD in which some of the vertebrae are not completely closed
What is closed spinal dysraphism?
Deficiency of at least two vertebral arches
What is meningocele?
Protrusion of the meninges through a defect in the skull or spine
What is myelomenigocele
Open spinal cord
