Development of the Brain Dennis T#2 Flashcards
What are the derivatives of forebrain (Prosencephalon)?
Telencephalon & Diencephalon
Derivatives of midbrain?
Mesencephalon
What are the hind brain (Rhombenccephalon) derivatives?
Metencephalon & Myelencephalon
Derivatives of the telencephalon and diencephalon?
Telencephalon: Lateral ventricles and cerebral hemispheres
Diencephalon: Thalamus hypothalamus epithalamus… third ventricle
Mesencehpalon derivatives?
Midbrain & aqueduct
Metencephalon and Myelecephalon derivatives?
Metencephalon: Pons and cerebellum and upper part of 4th ventricle
Myelencephalon: Medulla and lower part of 4th ventricle
What are the three flexures?
Midbrain (Mesencephalic) Flexure
Cervical flexure
Pontine flexure
What flexures are in the hindbrain?
Cervical flexure which separates hindbrain form spinal cord- defined at C1 superior rootlet @ foramen magnum
Pontine flexure which demarcates metencephalon from myelencephalon
Hindbrain derivatives?
Myelencephalon: medulla oblongata
Metencephalon: pons and cerebellum
Cavity of hindbrain is the 4th ventricle
What do the neuroblasts in alar plates form?
nucleus gracilis and nucleus cuneatus. Both associate with pathway for sensory info the PCML (DCML)
what are pyramids and where are the found?
Caudal myelencephalon
ventral structure consisting of CST fibers, important for regulating motor movement from cerebral cortex
In the rostral myelencephalon what happens when pontine flexure begins to move?
Pontien flexure causes walls of medulla to move laterally and the roof plate is thinned and cavity is part of 4th ventricle
Describe the relation of alar plates to the basal plates once pontine flexure is established?
Alar plate becomes lateral to the basal plates with expansion and flattening of the tissue
Neuroblasts from the basal plate develop into motor neurons and those nuclei organize themselves into columns. What are the columns?
GSE
SVE
GVE
Neuroblasts in the alar plates of he medulla form neurons that are arranged in columns similar to basal plates. What are they?
GVA
SVA
GSA
SSA
What forms neurons in olivary nuclei?
Neuroblasts from alar plates that migrate more ventrally
What do the walls of the metencephalon form?
Pons and cerebellum and the cavity forms 4th ventricle
In the metencephalon, what does the pontine flexure do?
forces walls of pons out laterally spreading the gray matter in the floor of 4th ventricle and neuroblasts of basal plate develop into motor nuclei
Cerebellum develops from ____.
Dorsal parts of alar plates
How does the cerebellum develop?
Cerebellar swellings project into 4th vent and fuse in median plane and overgrow rostral 4th vent pons and medulla. Alar plates will form central nuclei pontine cochlear nuclei
How does the choroid plexus form
Emendymal roof of the 4th ventricle is covered with Pia mater, which is derived from the hindbrain mesesnchyme. The pia mater and the ependymal roof is called the Tela Choroidea.
The tela choroidea proliferates and invests into 4th vent forming choroid plexus and then secretes ventricle fluid
When the outpockets from the 4th ventricle rupture what is formed?
Median and lateral apertures
What are the superior and inferior colliculi and where are they from?
Come from midbrain
Neuroblasts of the alar plates that migrate into the tectum
What do the neuroblasts of the basal plate form?
Midbrain Tegmental nuclei (Red nuclei involved in movement, reticular formation brain alertness, CN 3 and 4)
What forms the cerebral aqueduct?
midbrain
neural canal narrowing and it will connect 3rd and 4th ventricles
The swellings in the lateral walls of the 3rd ventricle in the diencephalon form ____.
Thalamus, hypothalamus and epithalamus
Describe development of thalamus.
Diencephalon
Develops and bulges into a cavity and fuses at the midline in ~70% of brains forming interthalamic adhesion
Describe hypothalamus development.
Diencephalon
Comes from neuroblasts in the intermediate zone. Endocrine and homeostatic nuclei develop and mammillary bodies form on the ventral surface
Epithalamus comes from __?
From roof and dorsal portion of lateral wall
What is the pineal gland?
median outgrowth of the roof of diencephalon
Pituitary gland development?
(BOARDS)
The anterior pituitary is endocrine tissue and the posterior is neural tissue.
Two embryonic sources:
- Hypophyseal diverticulum which is an upgrowth of roof of stomodeum (oral ectoderm)
- Neurohypophyseal diverticulum (Rathke’s pouch) downgrowth of diencephalon (neuroectoderm)
Describe the 4 steps to hypophyseal diverticulum development.
- projects from roof of stomodeum by 3rd week
- constricts its attachment from oral cavity
- Passes through cranium and contact infundibulum at week 5
- Regresses from oral cavity at 6th week
What does the telencephalon consist of?
Median part and two cerebral vesicles, primordia of the cerebral hemispheres. The cavity corms anterior 3rd ventricle but largely lateral ventricle.
What separates and defines caudate and lentiform (putamen and globus pallidus) nuclei?
Fibers of the IC pass through the corpus striatum
Holoprosencephaly (HPE), what is it?
incomplete separation of cerebral hemispheres. Most cases are associated with facial abnormalities such as cyclopia premaxillary agenesis, proboscis, single nostril, hypotelorism or facial clefts.
Severe and relatively common defect!
Describe the genetics of HPE.
Over 12 loci! SHH is the key player but there are others as well. It results in impaired forebrain dev and impacts FNP development.
Usually results in early fetal death
What is the lamina terminalis?
largest and most rostral end of the bundles of cerebral commissures. It extends from roof of diencephalon to optic chiasm. Within the lamina other commissures form!
What is the anterior commissure?
Interconnects temporal lobes within each hemisphere
Hippocampal commisure?
Interconnects the hippocampi within each hemisphere
Corpus Callosum?
Largest commissure links hemispheres along the length. It grows and extends beyond lamina terminalis anterior portion forms first and the posterior portion forms in fetal life
What is the septum pellicudium?
Thin plate of brain tissue containing nerve cells and fibers. Divides
How are layers produced in the cerebral cortex?
Cortical layers are laid down from deep to superficial. Youngest neurons are on the outer surface and oldest are the deepest.
Layer 6 is first produced Layer 1 is last produced
What is Lissencephaly?
Incomplete neural migration during months 3 and 4 of gestation. Initally the infant appears normal, but later develop siezures and profound mental deficiency and mild spastic quadriplegia. It is called smooth brain, they lack gyri and sulci.
What is agyria?
Seen in Lissencephaly
lack of gyri
What is pachygyri?
Lissencephaly
Thick and broad unorganized gyri
What is neuronal heterotopia?
Cells in aberrant positions compared to normal brain enlarged ventricles and malformation of the corpus callosum are also compon
Microcephaly?
Lack of coordinated brain and skull growth where calvaria and brain are small and face is normal sized. Zika virus, cytomegalovirus, rubella, toxoplasma gondii can cause it. Maternal alcohol abuse ionizing radiation, or autosomal recessive primary microcephaly are causes.
