Flashcards in CNS Embryology (5) Deck (37)
What structures are derived from endoderm?
Internal organs (viscera)
What three things develop from mesoderm?
2. Skeletal muscle
All derived from somites, which the mesoderm forms
What two things develop from ectoderm?
1. Neural structures
2. Epidermis of skin
During what week of gestation does brain development begin?
3rd week of gestation
What is the first step in the formation of the nervous system? What induces it?
Formation of the neural plate (thickening of the ectoderm in a rostral-caudal longitudinal band)
This is induced by the notochord
How is the neural tube formed from the neural plate? By when is it accomplished?
Neural tube is formed by the end of the 3rd week when the neural folds (elevated lateral margins of the neural plate) begin to fuse.
Fusion starts centrally and moves in both rostral and caudal fashions
By 4 weeks, how many vesicles have developed in the brain? What are they?
1. Prosencephalon (becomes forebrain)
2. Mesencephalon (becomes midbrain)
3. Rhombencephalon (becomes hindbrain)
By five weeks how many vesicles are in the brain? Which?
The prosencephalon gives rise to what 2 vesicles?
Telencephalon and diencephalon
The mesencephalon gives rise to what vesicle?
The rhombencephalon gives rise to what two vesicles?
Metencephalon and Myelencephalon
During which week does the neural tube close? Does anterior or posterior close 1st?
4th week; the anterior closes before posterior (25 vs. 27 days)
By what week do the cerebral hemispheres begin to enlarge?
What two cell types are CNS cells derived from?
What cell type differentiates into neuroblasts and glioblasts?
Ventricular zone neuroepithelial cells
What do neuroblasts form?
All neurons in the CNS
What 6 types of cells are derived from glioblasts?
1. Radial glial cells
6. Choroid plexus cells
Which cells are formed before neuroblasts differentiate into neurons? Why is that order necessary?
Radial glial cells. Migrating neurons attach to radial glial cells and travel to their final destination; since the radial cells arrange the neurons, they need to be present before.
When are most glial cells formed, other than radial glial cells?
After neuroblasts formation is complete
During what week due Microglia invade the CNS? What enables them to do so at this point?
During week 3, with the formation of cerebral blood vessels
In the embryonic neural tube, what structure separates the dorsal and ventral areas?
What type of neurons and nuclei does the alar plate in the embryonic neural tube form? What other type of neurons?
Sensory neurons and nuclei of the spinal cord, including dorsal root ganglia neurons.
(Alar plate is on the dorsal side of the sulcus limitans)
What is the adult corollary to the alar plate?
Neurons in the dorsal sensory horn
What types of neurons develop from the basal plate in the embryonic neural tube?
Motor neurons and nuclei of the spinal cord.
Adult corollary to basal plate
Ventral motor horn of the spinal cord
In the ____ month fetus, the conus medularis terminates at the end of the spinal column
In the ____ month fetus the spinal column begins to outgrow the cord and the conus ends at S1
In the 9 month fetus, the spinal cord ends at ____
What two conditions are the result of failure of the anterior neural pore to close?
What three conditions are the result of failure of the posterior neural pore to close?
1. Spinal bifida
What substance can be found in mother serum or in amniocentesis that is indicative of failure of neural tube closure?
Failure of mesodermal cells to form bony dorsal vertebrae that surround the spinal cord
Spina bifida occulta (SPO)
Why do individuals with SPO rarely develop neurological symptoms?
B/c the meninges and spinal cord/filum terminale are not actually involved in the defect, only the bone is affected.
What is the difference between spina bifida aperta w/ menigocele and w/ myelomenigocele?
Menigocele is an outpouring containing only the meninges. Myelomenigocele contains both meninges and spinal cord/filum terminale.
What is different about SPA from SPO clinically?
SPA may have severe neurological symptoms, whereas SPO usually doesn't have any neuro symptoms
What is the term for displacement/herniation of the cerebellar tonsils below the foramen magnum?