Development of the Brain (Dennis) Flashcards
Describe neurulation
Week 3: Notochord induces posterior aspect of embryo to form neural plate and neural groove
Week 4: Neural tube forms from 5th somite (neurulation)
Cranial 2/3 (up to 4th pair of somites) part of the neural tube becomes …
Caudal 1/3 part of the neural tube becomes…
- future brain
- future spinal cord
When does cranial neuropore close?
When does caudal neuropore close?
- 25 days
- 27 days
How does the brain proper develop?
Neural folds in the cranial region will fuse while the rostral neuropore will close to form the primary brain vesicles
What are the primary brain vesicles?
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
What happens at week 5?
Secondary vesicles form
Describe the development of secondary brain vesicles:
Forebrain divides into telencephalon and diencephalon
Hindbrain divides into metencephalon and myelencephalon
Label the parts of the developing brain
OK
What does the developing brain do morphologically at week 5?
-Grows rapidly and bends ventrally (unequal)
-The bending produces the midbrain/mesencephalic flexure (midbrain) and cervical flexure (midbrain-SC junction)
Unequal growth produces the pontine flexure
What is the significance of these flexures?
Cervical
Pontine
- divides the hindbrain from the spinal cord
- divides the hindbrain into the metencephalon (rostral) and myelencephalon (caudal)
What does the myelencephalon form?
What does the metencephalon form?
What does the cavity of the hindbrain form?
- medulla oblongata
- pons and cerebellum
- 4th ventricle and central canal in the medulla
Describe what happens to the caudal part of the myelencephalon
Neuroblasts in alar plate migrate to the marginal zone to form the nuclei gracilus and cuneatus (sensory nuclei)
Pyramids with CST fibers form at the ventral side
Describe what happens to the rostral part of the myelencephalon
Pontine flexure causes wall of medulla to move laterally and the roof plate is thinned
After this movement, alar plate becomes lateral to the basal plate (sensory is lateral to motor)
What do the neuroblasts at the basal plate of medulla form?
Motor neurons form three separate circles/columns - GSE, SVE, GVE
What do the neuroblasts of the alar plate of medulla form?
Sensory neurons form the lateral circles/columns: GVA, SVA, GSA, SSA
Somatic efferent column
CNs: III (in mesenscephalon)
IV, VI, XII (in rhombencephalon)
Special/branchial efferent column
Rhombencephalon has V, VII, IX, X, XI
Visceral efferent column:
Rhombencephalon has salivatory and dorsal nucleus of vagus Mesencephalon has the Edinger-Westphal nucleus (III)
General visceral afferent column:
Has the nucleus that receives info via CN IX and X
Special afferent column:
Has the nucleus of the tractus solitarius, which receives taste impulses via CN VII, IX and X
General afferent column:
Receives general facial sensation (CN V and VII)
Oral, nasal and auditory cavities (CN V, VII, IX and X)
Special somatic afferent column:
Has cochlear and vestibular nuclei (VIII)