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Anatomy 1-6 Development of the Spinal Nerves
Lecture 9.02 on formation of spinal nerves
21
Anatomy
Professional
09/05/2011

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Term
When does fusion of neural folds begin? Where does folding begin? How long does it last? What is this process called?
Definition
21 days; proceeds from middle in a cranio-caudal fashion; 4 days; neurulation
Term
What is the cranial portion of the neural tube destined to become?
Definition
brain
Term
What is the caudal portion of the neural tube destined to become?
Definition
spinal cord
Term
The inner layer of the newly formed neural tube is lined with neuroepithelial cells. What do these become?
Definition
neuroepithelium--->de-differentiate to become either neuroblasts (neuron precursors) or ependymal cells, which line the central canal of the neural tube and the ventricles of the brain.
Term
What do the collection of neuroblasts make up?
Definition
cell bodies make up the mantle layer (gray matter) of spinal cord, processes become marginal layer (white matter)
Term
Which ventricles of the brain make up the choroid plexus that will eventually produce CSF? What cells line these ventricles?
Definition
lateral, third, and fourth ventricles; ependymal cells
Term
The alar or basal plates, or the dorsal and ventral columns, respectively, become which parts of the spinal cord? What does the intermediolateral cell column become?
Definition
alar/dorsal column=dorsal horn of spinal cord, sensory information
basal/ventral column=ventral horn of spinal cord, motor information
intermediolateral cell column=autonomic neurons
Term
Which root grows into the laterally placed somites? At which spinal level would these roots contain autonomic information?
Definition
ventral root; T1-L2 and S2-S4
Term
How does the outgrowing axons of the newly forming ventral roots grow towards the dermamyotome?
Definition
The growth cone contains filopodia that direct them into the direction of the appropriate muscle masses
Term
How do the sensory nerves in the dorsal root ganglia connect with the spinal cord?
Definition
When the ventral root gets close enough to the dorsal root ganglia to form the spinal nerve, the sensory fibers grow until they reach the dorsal horn of the spinal cord.
Term
What do sensory neurons that grow towards the spinal cord synapse with once they enter the dorsal horn of the spinal cord
Definition
association neurons
Term
What is the dorsally located mass of cells derived from a somite called? The ventrally located? What do they become?
Definition
dorsal-epimere (neck/back)
ventral-hypomere (thoracic/abdominal walls)
Term
What is a myotome?
Definition
A group of muscles that are primarily innervated from a single spinal nerve.
Term
What is the condition that arises when the entire neural tube fails to close? When it partially closes?
Definition
craniorachischisis totalis; partial rachischisis, which usually occurs in lumbosacral region
Term
What is ancephaly?
Definition
absence of the head
Term
What is exencephaly?
Definition
brain is located outside of the skull
Term
What is induction?
Definition
the stimulation of a specific developmental pathway in one group of cells by a closely approximated group of cells.
Term
What is spina bifida?
Definition
vertebral arch fails to form completely due to disruption of induction;
occulta=incomplete arch; site covered by hair
cystica=meninges protruding into cyst through opening in arch
meningocele=herniation of meninges only
meningomyelocele=herniation with spinal cord/spinal nerve involvement. leads to hydrocephaly
Term
What do the neural crest cells become?
Definition
dorsal root ganglia, sympathetic chain ganglia, preaortic sympathetic ganglia, microscopic enteric ganglia, adrenal medulla cells, melanocytes
Term
What is the cause of Hirshsprung's disease (congenital megacolon)? What are its symptoms?
Definition
lack of ganglia in walls of large intestine; absence of peristalsis causes constipation
Term
What is a pheochromocytoma? How is it formed?
Definition
neural crest cells that fail to become part of the adrenal medulla become a catchecholamine-producing tumor, symptoms: HBP episodes, headaches, palpitations, nervousness
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