Embryology Flashcards
What is a placode?
A local thickening of the embryonic ectoderm layer that develops into a sensory organ or ganglion.
Which week does the neural plate appear?
Third week
What is the neural tube and how is it formed?
It begins as the neural plate, which is a placode. The lateral edges of the neural plate elevate and start approaching each other. When the neural folds fuse, they create the neural tube.
Where does fusion of the neural tube first occur?
In the cervical region, and then it moves in a cephalic and caudal direction.
When does the neuropores close?
At the 18- to 20-somite stage, which is around day 25, the cranial neuropore close, and the caudal one close 3 days later.
What are the first three dilations visible on the neural tube (the primary brain vesicles)? And which flexures can be seen?
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
- cervical flexure (junction of hindbrain and spinal cord)
- cephalic flexure (midbrain region)
What are the secondary brain vesicles, and which primary vesicles do they develop from?
Prosencephalon -> telencephalon and diencephalon
Mesencephalon -> remains the same
Rhombencephalon -> metencephalon and myelencephalon
What is the rhombencephalic isthmus?
It separates the mesencephalon from the metencephalon
What is the pontine flexure?
The boundary between metencephalon and myelencephalon
What is/are the derivatives of the telencephalon?
Cerebral hemispheres
What is/are the derivatives of the diencephalon?
Optic vesicle, thalamus, hypothalamus, pituitary
What is/are the derivatives of the mesencephalon?
Anterior (visual) and posterior (auditory) colliculi
What is/are the derivatives of the metencephalon?
Cerebellum and pons
What is/are the derivatives of the myelencephalon?
Medulla oblongata
What brain vesicle does the fourth ventricle develop from?
Rhombencephalon
What brain vesicle does the third ventricle develop from?
Diencephalon
Where does the cerebral aqueduct (aqueduct of Sylvius) develop from?
Mesencephalon
From where does the lateral ventricles develop?
Telencephalon
What is the neuroepithelium?
The neuroepithelium is the epithelium lining the wall of the closed neural tube. It is a pseudostratified epithelium that divide rapidly. They give rise to the primitive nerve cells (neuroblasts).
What is the mantle layer?
The mantle layer is a zone around the neuroepithelial layer consisting of neuroblasts. It gives rise to the gray matter of the spinal cord.
What is the marginal layer in the spinal cord?
The marginal layer is the zone around the mantle layer consisting of the nerve fibers arising from the neuroblasts bodies lying in the mantle layer. It will become the white matter of the spinal cord.
What are the basal plates of the spinal cord?
The ventral thickenings of the spinal cord that will form the motor area
What is the alar plate of the spinal cord?
The alar plate is the dorsal thickenings of the spinal cord that will give rise to the sensory areas.
In which sections of the spinal cord does the intermediate horn exist?
Contains the neurons of the sympathetic portion of the autonomic nervous system (ANS). Present at thoracic levels (T1-T12) and upper lumbar levels (L2 or L3).
