8: Brain Development Flashcards
What does the notochordal process induce formation of?
With what molecule?
Neural plate
Sonic Hedge Hog (SHH)
When does primary neurulation occur?
Day 22-23
Beginning of 4th week
What parts of the CNS form during primary neurulation?
Future Brain and lumbar Spinal Cord
What neuropore closes on day 25?
Cranial/Rostra Neuropore
What neuropore closes on day 27?
Caudal Neuropore
What part of the neural tube forms the brain?
Neural tube cranial to 4th somites
What are the three primary brain vesicles?
- Proencephalon: forebrain
- Mesencephalon: midbrain
- Rhombencephalon: hindbrain
What primary brain vesicles divide in the 5th week?
Forebrain (Prosencephalon)
Hindbrain (Rhombencephalon)
What does the prosencephalon give rise to?
- Telencephalon: cerebral hemipsheres and lateral venticles
- Diencephalon: thalami structures and 3rd ventricle
What are derivatives from the mesencephalon?
Midbrain and cerebral aqueduct
What does the rhombencephalon give rise to?
- Metencephalon: pons, cerebellum, and upper part of 4th ventricle
- Myelencephalon: medulla and lower part of 4th ventricle
What does the cervical flexure divide?
Hindbrain and spinal cord
Flexes forward
What does the pontine flexure divide?
Divides hindbrain into rostral metencephalon and caudal myelecephalon (pons/cerebellum and medulla)
Extending
What separates hindbrain from midbrain?
Isthmus Rhombencephali
What does the mesencephalic flexure divide?
Midbrain and forebrain
Flexes forward
What are some structures formed in the myelencephalon (medulla oblongata)?
- Nuclei Gracilus and Curneatus (sensory nuclei)
- Pyramids (white matter dealing with motor tracts)
- Alar and Basal Plates
What gives rise to sensory neurons that remain contained within the CNS?
Alar plate
What is the embryological origin of motor neurons that leave the CNS to go out to skeletal muscle?
Basal plate
What is the division between the alar and basal plates?
Which plate is medial and lateral?
Sulcus limitans splits alar (lateral) and basal (medial) plates
What gives rise to the cerebellum?
Dorsal parts of the alar plates
Eventually projects into 4th ventricle and overlaps pons and medulla
What coveres teh ependymal roof of the 4th ventricle?
Pia Mater
What is tela choroidea?
- Very thin part of pia mater that coveres lower part of 4th venticle
- Will invaginate the ventricle to form choroid plexus
How do the median and lateral apertures form?
Roof of 4th ventricle evaginates and those ruptures form the aperatures, allowing CSF to enter subarachnoid space
What gives rise to the superior and inferior colliculi?
Neuroblasts from alar plate that make tectum
Colliculi deal with vision/hearing, which are sensory
What gives rise to the tegmental nuclei?
What are some examples of tegmental nuclei?
Neuroblasts from basal plate that make tegmental nuclei
- Red Nuclei
- Reticular Nuclei
- CN III Nuclei
- CN IV Nuclei
What gives rise to substantia nigra?
Basal or alar plate that migrate ventrally
Are diencephalon structures grey or white matter?
Grey Matter
What gives rise to the hypothalamus?
Neuroblasts in intermediate zone
What gives rise to the pineal gland?
Median diverticulum of the caudal part of the epithalamus
What major structure is the caudate nucleus located adjacent to?
Lateral ventricle
What embryological layer gives rise to the anterior lobe of the pituitary gland?
Oral Ectoderm
- Arises from the stomoedum, leading to Rathke’s pouch
- Hypophyseal diverticulum
- When it fuses with posterior pituitary gland, rathke stalk degenerates
What embryological layer gives rise to the posterior lobe of the pituitary gland?
Neuroectoderm
- Arises from diencephalon (Neurohypophyseal diverticulum)
- Infundibulum forms posterior pituitary and infundibular stalk
What is holoprosencephaly?
Incomplete separation of cerebral hemispheres during development that can result in facial anomalies
Patient presents with epilepsy, headache, abnormal movements. Upon examination, he has a reduced frontonasal prominence and a cleft lip as well as some developmental delay. What disorder does he most likely have?
Holoprosencephaly
What can happen if there is agenesis of corpus callosum?
Seizures and mental deficiency
What are the layers of the cerebral cortex?
From top to bottom:
- Marginal Zone
- Intermediate Zone
- Ventricular Zone
Where are the older and newer neurons in the cerebral cortex?
- Older Neurons: Deeper (Layer VI)
- Newer Neurons: Superificial (Layer I)
Failure of neuronal migration during weeks 12-24 can result in what brain disorder?
Lissencephaly (agyria, smooth brain)
What is Lissencephaly characterized by?
Microcephaly
Ventriculomegaly
Minimal operculum of insula
Complete/partial agenesis of corpus collosum
What can cause microcephaly?
- Autosomal recessive primary microcephaly
- Ionizing Radiation
- Infectious Agents’
- Cytomegalovirus
- Rubella
- Toxoplasma gondii
- Maternal Alcohol Abuse
