Devo Flashcards
The NS develops from ___________, while the notochord develops from ___________.
- Ectoderm
- Mesoderm
What induces the development of the ectoderm by the 3rd week?
Notochord
What forms the neural plate thru its own thickening?
Anterior notochord
What are the faster-growing lateral ends of the thickening notochord called?
Neural folds
What does neurulation refer to?
Formation and closure of the neural tube
As the neural plate widens, it begins to form a shallow groove in its longitudinal aspect called the __________.
Neural groove
The narrower, posterior end of the neural groove will become the ___________, while the broader, anterior end will become the ____________
- Spinal cord
- Brain
As it grows, the neural groove deepens, and some of the cells in the lateral margin separate and migrate to a dorsal position to become the __________, eventually fusing the neural groove dorsally to form the _____________.
- Neural crest
- Neural tube
What are the (4) most important cell types that the neural crest will eventually differentiate into?
- Cranial nerve sensory ganglion cells
- Dorsal root ganglion cells
- Postganglionic autonomic ganglion cells (sympathetic & parasympathetic)
- Schwann cells
(also chromaffin cells of adrenal medulla and melanocytes)
Mesodermal cells alongside the neural tube will eventually begin to form __________.
Somites
Somites will eventually form __________, _____________, and ___________.
- Skeletal m.
- Vertebrae
- Dermis
What secondary vesicles are part of the prosencephalon (forebrain)?
- Telencephalon
- Diencephalon
What secondary vesicles are part of the mesencephalon (midbrain)?
Mesencephalon only
What secondary vesicles are part of the rhombencephalon (hindbrain)?
- Metencephalon
- Myencephalon
What brain regions are a part of the telencephalon?
- Cerebral cortex
- Basal ganglia
- Amygdala
- Hippocampus
(- Lateral ventricles and foramen of Monro)
What brain regions are a part of the diencephalon?
- Thalamus
- Hypothalamus
- Pituitary (neurohypophysis)
- Pineal gland
(- 3rd ventricle)
What brain regions are a part of the mesencephalon?
- Midbrain
- Cerebral aqueduct
What brain regions are a part of the metencephalon?
- Pons
- Cerebellum
(- 4th ventricle)
What brain regions are a part of the myelencephalon?
- Medulla
- Central canal
Which cephalic regions (2 of the 5) show the greatest rate of growth in early development?
- Cerebral hemispheres (telencephalon)
- Brainstem (myelencephalon)
Where does the cephalic flexure develop?
Just caudal to the midbrain, but still in the mesencephalon
Where does the pontine flexure develop?
What major structure grows out of this area?
In the pons
- Cerebellum
Where does the cervical flexure develop?
In the medulla
What are the 3 layers of the neural tube?
Ventricular zone, mantle zone, and marginal zone
During proliferation, grooves appear at the midpoints of the neural canal, called the______________.
Sulcus limitans
Neurocytes migrating dorsal to the sulcus limitans form the ______________, while those migrating ventral to it form the _______________, and those in b/w will form the __________________.
- Alar plate
- Basal plate
- Intermediolateral cell column
Cells of the intermediolateral cell column will go on to become what kind of neurons?
Autonomic neurons
Neurons in the alar plate contribute to _________ pathways, while those in the basal plate are_________ pathways
- Sensory
- Motor
Developing spinal nerves of the the alar plate contain ___ and ___ fibers, while developing spinal nerves of the basal plate contain ___ and ___ fibers
- GVA and GSA (afferent)
- GVE and GSE (efferent)
(recall: GVE is parasymp)
(no special senses innervated here)
Specifically, what types of neurons do GSE fibers innervate?
Alpha motor neurons
A 7 day old infant was evaluated because of intermittent vomiting that began a day after birth. A barium enema demonstrated contraction of the colon near the rectum and a length of colon proximal to the contraction was severely distended. Biopsy revealed an absence of autonomic ganglia cells in the colon. The most likely cause of this disorder was:
a. defective formation or migration of neural crest cells
b. failure of closure of the rostral neuropore
c. failure of closure of the caudal neuropore
d. lack of separation of the telencephalic vesicles
e. increased proliferation or migration of CNS neurocytes
Answer: a. defective formation or migration of neural crest cells
b. failure of closure of the rostral neuropore - anencephaly
c. failure of closure of the caudal neuropore – spina bifida
d. lack of separation of the telencephalic vesicles – cortical development
e. increased proliferation or migration of CNS neurocytes
During prenatal development, an abnormality occurs in which the neural crest cells fail to migrate properly. As a result, a number of different cell types fail to develop, but others are preserved. Which of the following cell types WOULD be found (preserved)?
a. Dorsal root ganglion cells
b. Autonomic ganglion cells
c. Chromaffin cells in the adrenal glands
d. Ventral horn motor neurons
e. Schwann cells
a. Dorsal root ganglion cells
b. Autonomic ganglion cells
c. Chromaffin cells in the adrenal glands
Answer: d. Ventral horn motor neurons – derived from Basal Plate
e. Schwann cells
All other cell types derived from neural crest.
What is the arrangement of the alar and basal plates in the medulla?
Alar plate becomes lateral to the basal plate
What are the old names for the median and lateral apertures, and in which part of the brain do they develop?
- Lateral aperture = foramen of Luscka
- Median aperture = foramen of Magendie
They develop in the Myelencephalon (medulla)
What are the 2 basic developmental divisions of the pons?
- Dorsal: tegmentum (extensions of myelencephalon)
- Ventral: basilar pons
The cells in the central region of the cerebellum are called the _____________, and those in the lateral regions will form the _______________.
- Vermis
- Cerebellar hemispheres
What cell type forms the “scaffold” of the cerebellum, and what cells layer over the top of this layer?
- Purkinje cells
- Granule cells
In the mesencephalon (midbrain), what are the 3 divisions (give spatial arrangement)?
- Tectum dorsally
- Tegmentum intermedially (continuation of pons and medulla)
- Peduncular region ventrally
(not that important) Each optic vesicle contributes to inductive interactions with the overlying ectoderm, thus forming the ______________________________.
Non-neural parts of the eye (such as the lens and cornea)
As the thalamus and hypothalamus grow, what ventricular space constricts?
3rd ventricle
Because of the rapid growth of the thalamus (grows faster than hypothalamus), what is the name of the bridge that forms b/w the 2 thalami?
Massa intermedia
(not that important) What are some structures that form on the ventral region of the hypothalamus?
The optic chiasm, mammillary bodies, tuber cinereum and the infundibulum
The lateral ventricles communicate with the lumen of the diencephalon (third ventricle) via the ______________.
Interventricular foramen of Monro
As the cerebral hemispheres expand, the roof plate fuses with the pia mater which contains vascular mesodermal tissue which forms the ______________ of the ________________.
Choroid plexus of the lateral ventricles
What arises from the medial surface of the telencephalic vesicle?
Hippocampal formation
Name the 3 major fiber bundles that cross hemispheres.
- Anterior commissure
- Corpus callosum
- Posterior commissure
What is spina bifida defined by?
What’s another name for it?
- Occurs when the posterior neuropore fails to close. Manifests by a failure of the vertebral canal to close properly
- Myeloschisis
Name and define the 3 types of spina bifida.
- Spina bifida occulta: a defect in the vertebral arches that is covered by skin and does not usually involve neural tissue. It typically occurs in the lumbosacral region and is normally marked by a patch of hair overlying the affected region.
- Spina bifida cystica: more serious; meninges protrude through the defect in the arches and skin forming a cyst-like sac (meningocele); neural tissure can come thru as well (meningomyelocele)
- Rachischisis: most serious; neural tissue becomes necrotic or fails to form.
What are the 3 NTDs that occur via ossification defects in the bones of the skull?
- Meningocele (protruding meninges)
- Meningoencephalocele (protruding meninges and neural tissue)
- Meningohydroencephalocele (protruding meninges, neural tissue, and ventricles containing CSF)
What characterizes exencephaly?
What condition does this typically lead to?
What is it called when the defect extends into the spinal cord?
Failure of the cephalic (rostral) neural tube to close, and results in failure of the skull to form, thus leaving the malformed brain exposed (incompatible w/life).
- Anencephaly (after brain tissue becomes necrotic)
- Craniorachischisis
Abnormal accumulation of CSF within the ventricular system can lead to _____________.
Which part of the ventricular system is usually affected?
Where does the fluid accumulate?
- Hydrocephaly
- Blockage or stenosis to the aqueduct of Sylvius
- Lateral ventricles (skull expends since sutures aren’t fused yet)
What is Dandy-Walker syndrome?
A type of hydrocephalus: Congenital abnormality of the fourth ventricle with failure of foramens Luschka & Magendie to form, resulting in an enlargement of the fourth ventricle.
- Also characterized by complete absence of the cerebellar vermis and cyst formation near the internal base of the skull
(syndrome can appear dramatically or develop unnoticed)
What is Arnold-Chiari malformation?
Caudal displacement (and herniation) of the posterior cranial fossa structures, namely the cerebellum, through the foramen magnum. (Tx: use surgery to remove some of the bone)
What is the term that describes a cranial vault that is smaller than normal? Is this due to lack of brain devo or lack of skull devo or what?
Microcephaly
- Lack of brain devo
A two day old female infant presents with a small pigmented area at the midline on her lower back. Close examination reveals a small tuft of delicate hairs associated with a small cutaneous dimple. Which of the following most closely signifies with this defect?
a. Rachischisis
b. Encephalocele
c. Spina bifida aperta
d. Spina bifida cystica
e. Spina bifida occulta
a. Rachischisis – complete failure of neural tube to close
b. Encephalocele – meningocele of the cranium
c. Spina bifida aperta – skin not closed
d. Spina bifida cystica – sac-like defect is exposed
Answer: e. Spina bifida occulta
A stillborn infant was noted to have a grossly abnormal skull and cerebrum. The parietal bones, most of the occipital bones, and most of the frontal bones above the orbits were absent. A malformed remnant of the cerebrum, with few recognizable structures, was exposed at the site of the skull defect. The most likely explanation for this malformation was:
a. defective formation or migration of neural crest cells
b. failure of closure of the rostral neuropore
c. failure of closure of the caudal neuropore
d. blockage of the cerebral aqueduct
e. increased proliferation or migration of CNS neurocytes
a. defective formation or migration of neural crest cells (see earlier questions)
Answer: b. failure of closure of the rostral neuropore (anencephaly or exencephaly)
c. failure of closure of the caudal neuropore (spina bifida)
d. blockage of the cerebral aqueduct (hydrocephalus)
e. increased proliferation or migration of CNS neurocytes (enlarged cortex)
A 7 year old boy is brought to the pediatrician by his mother, who complains that the boy has had progressive difficulty seeing/reading the assignments posted on the board by the teacher. Examination reveals a boy who is noticeably small for his age, has partial vision loss in both eyes peripherally, but otherwise appears healthy. MRI of the brain reveals a craniopharyngioma – Rathke’s pouch tumor – which is an aberrant outpocketing of the stomodeum. Which one of the following is most directly involved in the developmental defect seen in this boy?
a. Adenohypophysis
b. Neurohypophysis
c. Optic chiasm
d. Hypothalamus
e. Thalamus
Answer: a. Adenohypophysis – anterior pituitary
b. Neurohypophysis – posterior pituitary
c. Optic chiasm – symptom of expanding tumor
d. Hypothalamus – large hormonal & autonomic symptoms
e. Thalamus – sensory loss & abnormalities
A child is born with a large mass on the forehead, a partially cleft nose, and ocular hypertelorism (widely spaced orbits). CT and MRI reveal a defect in the frontal bone and a mass containing fluid, portions of the frontal lobe, and a cavity that is continuous with the anterior horn of the right lateral ventricle. Which of the following best describes this type of mass?
a. Meningocele
b. Meningoencephalocele
c. Meningohydroencephalocele
d. Meningomyelocele
e. Microencephaly
a. Meningocele – meninges only
b. Meningoencephalocele – meninges + neural tissue
Answer: c. Meningohydroencephalocele – meninges + neural tissue + ventricle
d. Meningomyelocele – spinal cord lesions
e. Microencephaly – undersized brain (and skull)
The two optic vesicles are attached to each side of which secondary vesicle (of the 5)?
Diencephalon
When taken throughout pregnancy, this substance reduces the incidence of NTDs by as much as 70%
What is folic acid?
