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21 Cards in this Set

  • Front
  • Back
Write short notes on the formation of the neural tube
Neural tube is formed when the lateral folds fuse dorsally.
Its closure begins at the level of the future hindbrain and zips up rostrally and caudally
Where does rostral neuropore locate? When does it close?
At the site of the future forebrain and closes as the telenchephalic vesicles develop
Where does caudal neuropore locate? When does it close?
At the site of the caudal end of the future spinal cord and ultimately closes over
What is the germinal layer?
Germinal layer is the most medial layer of the neural tube wall. initially proliferative, but ultimately exhausted and becomes ependyma (squamous - columnar)
What is the mantle layer?
The mantle layer consists of primitive neurons and spongioblasts which form the grey matte of the CNS. It is the middle layer of the neural tube except where it is the external in the cerebral hemispher
What is the marginal layer?
The marginal layer consists of primarily axons of the mantle layer which form the white matter of the CNS. It is the outer most layer except in the cerebral hemisphere where it is in the middle layer
Define the following terms: sulcus limitans, alar plate, basal palte
Sulcul limitans: A longitudinal groove that develops in the lateral wall of the neural tube extending from the mid-brain to the caudal spinal cord

Alar plate: dorsal bulge of the embryonic neural tube, destined to develop into the dorsal horn of the spinal cord (i.e. primarily sensory)

Basal plate: ventral bulge of the developing neural tube, destined to develop into the ventral horn of the spinal cord (i.e. primarily motor)
How is the dorsal median septum formed?
the dorsal growth of the two halves of the alar plate forms a vertical wall between the two dorsal halves of the spinal cord
How is dorsal grey columns formed?
formed from the alar plate neuroblasts
How is ventral median fissure formed?
the ventral growth of the two halves of the basal plate forms a cleft between the two ventral halves of the spinal cord
How is ventral grey columns formed?
formed from the basal plate neuroblasts
Why do intumescences form in the spinal cord?
Intumescences are enlarged regions of the spinal cord. The continued growth of a neuron depends on it innervating a structure (effector/receptor), otherwise it degenerates. Intumescences occur because of the large amount of tissue requiring innervation within the limbs.
What is the origin of the ventricular system?
the neural tube in the region of the brain
What part of the ventricular system forms in each division of the brain?
2 lateral ventricles → telencephalon

third ventricle → diencephalon

mesencephalic aqueduct → mesencephalon

forth ventricle → metencephalon & myelencephalon

spinal canal → spinal cord
Write short notes of the formation of the cerebellum including the cellular migration
The cerebellum arises as a dorsal outgrowth of the metencephalon to form a cauliflower like mass. The differentiating mantle cells (no longer dividing) form purkinje cells and neurons of the cerebellar nuclei. The dividing germinal cells migrate to the surface of the cerebellum to form the external germinal layer, giving rise to the granule cell layer & stellate cells of the molecular layer. Thus grey matter → superficially to the axons of the white matter
How does crus cerebri/cerebral peduncles form?
formed from caudally growing neuronal processes from the cerebral cortex.
How does internal capsule form?
formed from efferent axons from the telencephalon which continue through the midbrain as the crus cerebri/cerebral peduncles
How does hypophysis (pituitary gland) form?
formed by the ventral diencephalic outgrowth (of neurohypophysis) and a dorsal outgrowth of the oral ectoderm
How does telencephalic vesicle form?
huge outgrowths of prosencephalon that extend dorsally and laterally to form the cerebral hemispheres
Which part of the spinal cord has intermediate horns?
Thoracic, lumber, cranial, and sacral part of the cord.
(i.e. expect cervical part where no autonomic nervous system go through)
How do vertebrae form?
each vertebre is formed from four 1/2 sclerotomes.

Each sclerotome devides into cranial and caudal halves during development.
Adjacent parts of four sclerotomes fuse to form one vaterbrae