Brain Embryology Flashcards
Neuralation
Neural plate → Neural tube
Neural plate lengthens, lateral edges elevate to form the neural folds and the depressed mid region forms the neural groove.
Neural folds approach each other in the midline and fuse.
Fusion begins in cervical region (22 days) and proceeds craniocaudally.
How does the cephalic end of the neural tube communicate with the amniotic cavity until fusion is complete?
Cephalic end communicates with the amniotic cavity via the anterior (cranial) neuropore.
How does the caudal end of the neural tube communicate with the amniotic cavity until fusion is complete?
Caudal end communicates with the amniotic cavity via the posterior (caudal) neuropore.
When does the cranial neuropore close?
~25 days
When does the caudal neuropore close?
28 days
When and how does the pontine flexure develop?
Weeks 5-8.
Dorsal flexion at the site of the developing pons.
Metencephalon folded back on myelencephalon.
When and how does the cervical flexure develop?
Weeks 5-8.
Ventral flexion between the myelencephalon and the spinal cord.
When and how does the mesencephalic flexure develop?
Week 4/5.
Prosencephalon is folded under the mesencephalon.
What does the alar plate in the spinal cord become?
Sensory dorsal horn
What does the basal plate in the spinal cord become?
Motor ventral horn
When do the spinal nerves begin to develop?
Week 6
What is the main derivative of the myelencephalon?
The medulla oblongata
What does the basal plate of the myelencephalon contain?
3 groups of motor nuclei
What are the three groups of motor nuclei in the basal plate of the myelencephalon?
1 - Medial somatic efferent
2 - Intermediate special visceral efferent
3 - Lateral general visceral efferent
What is the somatic efferent motor column?
Continuation of somatic efferent group from basal plate of myelencephalon.
What does the somatic efferent motor column contain in the myelencephalon?
Neurons of the hypoglossal nerve (supplies tongue musculature)
What does the somatic efferent motor column contain in the metencephalon and the mesencephalon?
Neurons of abducens (VI), trochlear (IV) and oculomotor (III). These nerves supply eye musculature.
What is the special visceral efferent motor column?
Extension of the special visceral efferent group into the metencephalon
What does the special visceral efferent motor column contain in the myelencephalon?
Neurons of the accessory (XI), vagus (X) and glossopharyngeal (IX) nerves.
What does the general visceral efferent group of neurons from the basal plate of the myelencephalon contain?
Motor neurons which supply the involuntary musculature of the respiratory tract, intestinal tract and heart.
What does the alar plate of the myelencephalon contain?
Three groups of sensory relay nuclei
What are the three groups of sensory nuclei in the alar plate of the myelencephalon?
1 - Somatic afferent
2 - Special afferent
3 - General visceral afferent
What do the alar plates of the metencephalon contain?
Three groups of sensory nuclei
What are the three groups of sensory nuclei in the alar plate of the metencephalon?
1 - Lateral somatic afferent
2 - Special afferent
3 - General visceral afferent
Where do the pontine nuclei originate?
The alar plate of the metencephalon
What do the basal plates of the metencephalon contain?
Three groups of motor neurons
What are the three groups of motor neurons in the basal plates of the metencephalon?
1 - Medial somatic efferent
2 - Special visceral efferent
3 - General visceral efferent
What are the initial layers of the cerebellar plate?
Neuroepithelial
Mantel
Marginal
How is the external granular layer formed?
During week 12 - cells formed by neuroepithelium migrate to surface of cerebellum to form external granular layer.
What does the external granular layer give rise to?
Granule cells
When are granule cells produced by the external granular layer?
6th month of development
What are produced from the proliferating cells in the cerebellar white matter?
Basket cells
Stellate cells
What is formed from the alar plates in the mesencephalon?
Superior and inferior colliculi
Substantia nigra and red nucleus
What is the function of the inferior colliculi?
Synaptic relay stations for auditory reflexes
What is the function of the superior colliculi?
Correlation and reflex centres for visual impulses
What is found in the basal plates of the mesencephalon?
Two groups of motor nuclei
What are the two groups of motor nuclei in the basal plates of the mesencephalon?
1 - Medial somatic efferent - oculomotor (III) and trochlear (IV)
2 - General visceral afferent - nucleus of Edinger-Westphal - innervates sphincter pupillae.
What is formed by the marginal layer of the basal plate?
Crus cerebri
What is the crus cerebri?
Pathway for descending fibres from the cortex to the spinal cord
What makes up the prosencephalon?
Telencephalon and diencephalon
What does the telencephalon form?
Cerebral hemispheres
What does the diencephalon form?
Optic cup Optic stalk Pitutary Thalamus Hypothalamus Epiphysis
