17: Development Of The Brain

Question 1

When does brain start developing? From what?

Answer 1

3rd week, from neural tube

Question 2

Primary vesicles

Answer 2

prosencephalon, mesencephalon, rhombencephalon

Question 3

Secondary vesicles: in order from superior to inferior

Answer 3

Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

Question 4

When do secondary vesicles and brain flexures appear?

Answer 4

5th week

Question 5

Brain flexure

Answer 5

Space into which neural tube development is limited, but there is extensive growth -> NT bends

Question 6

Two ventral flexures

Answer 6

Midbrain flexure, pontine flexure

Question 7

1 dorsal flexure

Answer 7

Cervical flexure

Question 8

What does the pontine flexure demarcate?

Answer 8

Metencephalon and myelencephalon

Question 9

What does the cervical flexure demarcate

Answer 9

Hindbrain and SC

Question 10

What types of fibers pass through the corpus striatum

Answer 10

Fibers of the internal capsule

Question 11

Interthalamic adhesion

Answer 11

Thalamus fuses at midline in 70% of brains

Question 12

Mammillary bodies are on the ventral surface of what structure?

Answer 12

Hypothalamus

Question 13

Weeks 3-6 in hypophyseal diverticulum (pituitary) development

Answer 13

Week 3: diverticulum projects from roof of stomodeum
Week 4: constricts attachment
Week 5: passes through cranium, contacts infundibulum
Week 6: regresses from oral cavity

Question 14

Three parts of the anterior pituitary + three parts of the posterior pituitary

Answer 14

Anterior: pars anterior, pars tuberalis, pars intermedia
Posterior: medial eminence, pars nervosa, infundibulum

Question 15

Four tegmental nuclei (in mesencephalon)

Answer 15

Red, reticular, CN3, CN 4

Question 16

Lamina terminalis

Answer 16

Most rostral commissure, extending from roof of diencephalon -> optic chiasm

Question 17

Septum pellucidum formation

Answer 17

Forms from lamina terminalis stretching

Question 18

Anterior commissure

Answer 18

Connects temporal lobes within each hemisphere

Question 19

Hippocampal commissure

Answer 19

Interconnects hippocampi within each hemisphere

Question 20

Corpus callosum

Answer 20

Largest commissure, connecting the two hemispheres

Question 21

Volume of brain at birth

Answer 21

Only about 25% of adult volume

Question 22

Two ways the post-natal brain grows

Answer 22

Neurons increase in size + myelination of axons

Question 23

Laying down cortex layers

Answer 23

Lay down from deep to superficial; neurons migrate through deep layers to establish superficial layers

Question 24

Holoprosencephaly

Answer 24

I’m complete separation of cerebral hemispheres

Question 25

S/S of holoprosencephaly

Answer 25

Facial abnormalities: cyclopia, premaxillary agenesis, proboscis, single-nostril, hypotelorism, facial clefts

Question 26

Biggest genetic contribution to holoprosencephaly

Answer 26

SHH

Question 27

How does holoprosencephaly develop?

Answer 27

Impaired forebrain development, impacts FNP

Question 28

Agenesis of corpus callosum: associated with…

Answer 28

More than 50 different congenital syndromes, seizures, mental deficiencies. Can be asymptomatic

Question 29

Lissencephaly

Answer 29

Incomplete neuron migration during 3rd-4th month of gestation

Question 30

Presentation of lissencephaly

Answer 30

Infant initially appears normal, but will develop profound mental deficiency, seizures, and mild spastic quadriplegia

Question 31

Cerebral surface in lissencephaly

Answer 31

Can have pachygyria (broad, thick gyri) or agyria (lack of gyri)

Question 32

Neuronal heterotopia

Answer 32

In lissencephaly, cells are in aberrant positions compared to normal brain

Question 33

Microcephaly

Answer 33

Brain and calvaria are small, but face is normal size

Question 34

What causes microcephaly physiologically?

Answer 34

Inadequate pressure from growing brain -> small neurocranium

Question 35

Some potential causes for microcephaly

Answer 35

Autosomal recessive, ionizing radiation, maternal EtOH, infectious agents (cytomegalovirus, Zika, Rubella, Toxoplasma gondii)