WEEK 2: EMBRYOLOGY OF THE SPINAL CORD Flashcards
Describe how the process of Gastrulation.
1.The cells in the inner mass undergo differentiation and form epiblast and hypoblast.
2.Some epidermal cells migrate to the middle and form a primitive streak.
3.SOME OF THE CELLS ENTER INTO THE PRIMITIVE STREAK AND enter the hypoblast forming turning it into an ENDODERM.
4.Remaining epiblast cells will the form the ECTODERM.
5.Majority of the epiblast cells occupying the middle of the Endoderm and ectoderm will form a mesoderm.
Which layer is the Nervous system derived from?
The ECTODERM.
Describe how the neural tube is formed.
1.The notochord secretes GROETH FACTOR which stimulate the ectoderm to differentiate into NEUROECTODERM.
2.There is formation of a NEURAL PLATE which will rise on the lateral edges to form NEURAL FOLD.
3.The neural folds move towards each other and form a neural tube.
4.The surrounding cells form a NEURAL CREST.
5.The caudal part of the neural tube will close to form a spinal cord.
State the anomaly associated with the spinal cord formation.
1.Spina bifida.
Incomplete closer of the caudal end of the neural tube.
Describe the 3 types of Spina bifida.
1.Spina bifida occulta: Incomplete closer of the vertebral column, there is protrusion without the spinal cord.
2.Meningocele; There is protrusion of the meninges through the unclosed spinal column.
3.Myelomeningocele: There is the protrusion of both the spinal cord and the meninges through the spinal column. It is associated with severe disability.
State the anomaly associated with the formation of the brain.
1.Anencephaly: Incomplete closure of the cranial part of the neural tube.
Absence of brain and skull.
The newborns do not survive for long, few hours to days after birth they die.
Name the cells in the neural tube wall that forms the neurons and glial cells.
Neuroepithelial cells.
State the 3 types of the neuroepithelial cells and what they form.
GLIOBLASTS
*Glioblasts migrate from the neuroepithelial layer to the mantle and marginal layers
1.In the mantle layer they differentiate into protoplasmic and fibrillar astrocytes
2.In the marginal layer oligodendroglia cells differentiate. This cell forms myelin sheaths around the ascending and descending axons
NEUROBLASTS
1.The neuroepithelial cells differentiate into neuroblasts, which form the mantle layer (gray matter of the spinal cord).
2.Nerve fibers emerging from these neuroblasts constitute the marginal layer (the white matter of the spinal cord).
Neuroblasts form neurons.
INTERNAL LAYER Ependyma
*Simple cuboidal epithelium ALSO covering the choroid plexus.
Where do microglial cells form from?
The microglia cells differentiate from the mesenchymal cells surrounding the central nervous system.
What part of the neural tube form the white and gray matter?
GRAY MATTER: Mantle layer
WHITE MATTER: Marginal layer
What do the following form from?
*Dorsal horn
*Ventral horn
*Lateral horn
Alar plate
Ventral plate
Basal plate
State the structures above the sulcus limitans and their derivatives.
1.Dorsal Columns
*Derivative of alar plate (neural tube)
Portion of central nervous system
Neurons in the dorsal columns constitute afferent nuclei
2.Dorsal rootlet
*Derivative of neural crest
Portion of peripheral nervous system
Composed of Schwann cells and cell processes for sensory
neuroblasts in spinal (dorsal root) ganglion
3.Afferent sensory neuroblasts in spinal (dorsal root) ganglion
*Derivative of neural crest
Portion of peripheral nervous system
Associated with afferent (sensory) function
State the structures below the sulcus limitans and their functions.
1.Ventral Columns
*Derivative of basal plate (neural tube)
Portion of central nervous system
Neurons in the dorsal columns constitute efferent nuclei
2.Lateral Columns
*Derivative of basal plate (neural tube)
Portion of central nervous system
Neurons in the lateral columns constitute efferent nuclei
3.Ventral roots of spinal nerve*
*Derivative of neural tube
Portion of central nervous system
Cell processes for motor neuroblasts in ventral horn
