development of the brain

Question 1

when and where does the neural plate and neural groove form?

what is it induced by?

Answer 1

develop on the posterior aspect of the trilaminar embryo (3 weeks)

Induced by the notochord

Question 2

When does Neurulation begin and what components develop into what?

Answer 2

Neurulation begins 4th week
-Cranial 2/3 = 4th pair of somites and becomes future brain

-Caudal 1/3 = Future spinal cord

Question 3

Where does the neural tube form?

When does the neurotubes close

Answer 3

Neural tube first forms at the 5th somite

Cranial neurotube closes at 25 days

Caudal neurotube closes at 27 days

Question 4

what are the three primary brain vesicles

Answer 4

Forebrain: Prosencephalon

Midbrain: Mesencephalon

Hindbrain: rhombencephalon

Question 5

What are the 5 secondary brain vesicles and when do they develop?

Answer 5

5th week

Telencephalon and Diencephalon (via the forebrain division)

Mesencephalon (midbrain does not divide)

Metencephalon, and Myleencephalon (via division of the hindbrain)

Question 6

What are the walls and cavities derived from the secondary vesicles: Telencephalon

Answer 6

Cerebral hemispheres

Lateral ventricles

Question 7

What are the walls and cavities derived from the secondary vesicles: Diencephalon

Answer 7

Thalamus, etc

Third ventricle

Question 8

What are the walls and cavities derived from the secondary vesicles: Mesencephalon

Answer 8

Midbrain

Cerebral Aqueduct

Question 9

What are the walls and cavities derived from the secondary vesicles: Metencephalon

Answer 9

Pons, Cerebellum

Upper part of fourth ventricle

Question 10

What are the walls and cavities derived from the secondary vesicles: Myelencephalon

Answer 10

Medulla

Lower part of fourth ventricle

Question 11

What are the three flextures of the brain and when do they occur and what direction

Answer 11

Midbrain or mesencephalic flexure (towards trunk bend)

Cervical flexure (hindbrain/SC junction and flexes toward the trunk)

Unequal growth produces the pontine flexure (extension away from trunk) occurs at the Meten-myelencephalon junction

These occur at week 5 and lead to producing considerable variation position of the gray and white matter

Question 12

what makes up the hindbrain

Answer 12

Cervical flexure to Pontine flexure

Myelencephalon - Medulla oblongta

Metencephalon - Pons and Cerebellum

Cavity: Fourth ventricle and central canal in the medulla

Question 13

What makes up the caudal mylencephalon

Answer 13

Alar plates migrate into the marginal zone give rise to
nucleus gracilus, nucleus cuneatus

Pyramids consisting of corticalspinal tracts

Question 14

What makes up the rostral myelencephalon

Answer 14

is wide and flat

Pontine Flexure: causes the walls of medulla to move laterally

Roof plate: greatly thinned
cavity becomes part of future 4th ventricle

Alar plates become lateral to the basal plates
motor nuclei develop medial to sensory nuclei

Question 15

What do neuroblasts in the basal plate of the medulla develop to

Answer 15

columns motor neurons. efferent

General somatic efferent
special viscereal efferent
general visceral efferent

Question 16

What do neuroblasts in the alar plate of the medulla develop to

Answer 16

columns of Afferent neurons

general visceral afferent
special visceral afferent
general somatic afferent
special somatic afferent

Question 17

What develops out of the metencephalon

Answer 17

forms the pons and the cerebellum

superior part of the 4th ventricle

Cerebellum develops from dorsal parts of alar plates

• cerebellar swellings project into 4th ventricle
• fuse in median plane
• overgrows rostral 4th ventricle and overlap the medulla and pons

Question 18

How is the choroid plexus formed

Answer 18

Ependymal roof of 4th ventricle is covered externally by pia mater
-these two together make up the tela choroidea

the tela choroidea will invaginate the 4th ventricle to form the choroid plexus

Question 19

what is the epithelial lining of the choroid plexus derived from? the stroma?

Answer 19

neuroepithelium

stroma is the mesenchymal cells

Question 20

how are the median and lateral aperatures formed

Answer 20

the roof of the 4th ventricle evaginates in three locations which will rupture making the apertures
-this allows for the CSF to enter the subarachnoidspace

Question 21

What do the neuroblasts of the alar plate in the midbrain give rise to

Answer 21

Tectum which will form the superior and inferior colliculi

Question 22

What do neuroblasts of basal plates of the midbrain give rise to

Answer 22

tegmental nuclei (red nuclei, reticular nuclei, CN III, and IV nuclei

Question 23

What does the substantia nigra derive from

Answer 23

is still arguable could be basal plate or alar plate cells that migrate ventrally

Question 24

how is the cerebral aqueduct formed

Answer 24

formed in the midbrain due to neural canal narrowing

Question 25

What develops in the Diencephalaon

Answer 25

swellings of the lateral walls of the third ventricle will form the thalamus, hypothalamus and the epithalamus Epithalamic sulcus seperates the thalamus and epithalamus Hypothalamic sulcus seperates the thalamus and the hypothalamus

Question 26

what does the the hypothalamus arise from?

Answer 26

neuroblasts in intermediate zone - Endocrine and homeostatic nuclei develop - Mamillary bodies form on ventral surface of the hypothalamus

Question 27

How does the epithalamus develop?

Answer 27

develops from the roof and dorsal portion of the lateral wall forms the epithalamic swellings which are large but then will become relatively small

Question 28

How does the Pineal gland form

Answer 28

Develops as a median diverticulum of the caudal part of the roof of the diencephalon -proliferation of cells in its walls converts it into the solid cone shaped gland

Question 29

How does the Anterior lobe of the Pituitary gland develop

Answer 29

Oral ectoderm Hypophyseal diverticulum (rathkes pouch) from the roof of the stomodeum migrates up gives rise to: Pars anterior pars tuberalis pars intermedia the tissue type: adenohypophysis connection to the oral cavity degrades week 6

Question 30

How does the Posterior lobe of the Pituitary gland develop

Answer 30

Neuroectoderm Neurohypophyseal diverticulum from the floor of the diencephalon migrate down (connected to brain via the infundibulum (passes between developing bones of the cranium)) - Pars nervosa - Infundibular stem - Median eminence

Question 31

What consists in the telencephalon and how does it form the cerebral hemispheres

Answer 31

median part and two telencephalic/cerebral vesicles, primordia of the cerebral hemispheres the median cavity will form the anterior 3rd ventricle communication of cerebral hemispheres with 3rd ventricle is done via the interventricular foramina The hemispheres become C-shaped -due to cortex rapidly proliferating but deeper nuclei do not

Question 32

When do the optic vesicles appear on the telencephalon

Answer 32

as closure of the rostral neuropore occurs the optic vesicle will appear

Question 33

Where does the choroid plexus form in the 3rd ventricle

Answer 33

the medial wall of the cerebral hemisphere which is continuous with the roof of the 3rd ventricle will develop the choroid plexus

Question 34

How does the falx cerebri form

Answer 34

from mesenchyme trapped in the longitudinal fissure which occurs via the cerebral hemispheres expanding to meet each other in the midline causing the medial surfaces to flatten

Question 35

Cavities of what secondary brain vesicles make up the 3rd ventricle

Answer 35

Telencephalon (anterior part) | Diaencephalon (the rest)

Question 36

Holoprosencephaly

Answer 36

Incomplete separation of the cerebral hemispheres Defectss in forebrain development often cause facial anomalies resulting from a reduction of FNP Cyclopia, premaxillary agenesis, proboscis, single-nostril, hypotelorism, facial clefts genetic that causes an inhibition of cholesterol syntesis

Question 37

What are the Cerebral commissures and what are they connecting

Answer 37

groups of nerve fibers interconnecting the cerebral hemispheres -lamina terminalis: rostral end of the forebrain Anterior commisure and hippocampal commissure form first - anterior interconnects the olfactory bulb with the hemispheres and temporal lobes - Hippocampal connects the hippocampal formations Posterior commisure: posterior to upper portion of the cerebral aqueduct and is important in the bilateral pupillary light reflex Corpus callosum forms the hemispheres -anterior portion forms first then the posterior portion in fetal life Lamina terminalis forms the septum pellucidum which is a thin plate of brain tissue containing nerve cells and fibers

Question 38

Agenesis of corpus callosum

Answer 38

complete or partial absence of the corpus callosum the condition may be asymptomatic but seizure and mental deficiency are common

Question 39

How does growth of the cerebral hemispheres occur

Answer 39

Cortex is initially ssmooth but growth gives the development of gyrus and sulci has zones: ventricular, intermediate and marginal and subventricular cortical layers are layed down deep to superficial - neurons migrate through the deeper layer to establish superficial layers - inside out development

Question 40

Lissencephaly

Answer 40

incomplete neuronal migration to cerebral cortex during 3-4 months of gestation smooth cerebral surface - Pachygyria: broad thich gyri - Agyria: lack of gyri - Neuronal heterotopia: cells in aberrant positions compared to a normal brain - enlarged ventricles and malformed corpus callosum initially appear normal and then develop seizures, profound mental deficiencies, spastic guadriplegia

Question 41

Microcephaly

Answer 41

calvaria and brain are small but face is normal sized significant mental deficiencies due to brain underdevelopment reduction in brain growth Causes: - Autosomal recessive primary microcephaly - ionizing radiation - infectious agents (cytomegalovirys, rubella virus, toxoplasma gondii) - Maternal alcohol abuse