The Human Brain During the Third Trimester

CEREBELLAR

HEMISPHERE

CEREBELLAR

HEMISPHERE

External germinal

layer

Raphe migration

(penetrating the medullary

arcuate nucleus)

Raphe nuclear complexRaphe nuclear complex

Reticular

formation

Reticular

fo rmation

Reticular

formation

Reticular

fo rmation

Reticular

formation

Reticular

fo rmation

Flocculus

(HX)

Flocculus

(HX)

Tr anspontine corticofugal tract

(thick longitudinal bundles)

Pontocerebellar fiber s

(thin transve rse bundles)

Pontocerebellar fiber s

(decussation)

PONSPONS

MEDULLAMEDULLA

SPINAL CORD

Pontine

gray

Pontine

gray

Choroid

plexus

Choroid

plexus

Choroid

plexus

Choroid

plexus

Ve ntral cochlear nucleus

Spinocerebellar tracts

Middle cerebellar peduncle

Spinoce

rebellar tract

s

Spinocer

ebellar tracts

Lateral corticospinal tract

Ventral white commissure

Spinocephalic (spinothalamic)

tracts

Ve ntral corticospinal tract

Intraspinal tracts

(intermingled with the medial

longitudinal fasciculus and

tectospinal tract)

Hypoglossal nucleus? (XII)Hypoglossal nucleus? (XII)

Medial longitudinal

fasciculus and

tectospinal tracts?

Medial longitudinal

fasciculus and

tectospinal tracts?

Pyramidal

decussation

Pyramidal

decussation

Lateral

reticular nucleus

Lateral

reticular nucleus

Lateral

reticular

nucleus

Lateral

reticular

nucleus

Inferior olive

(principal nucleus)

Inferior olive

(principal nucleus)

Dorsal

accessory

olive

Dorsal

accessory

oliv e

Myelination gliosis

(lateral funiculus)

Myelination gliosis

(ventral funiculus)

Germinal and transitional

structures in italics

Germinal and transitional

structures in italics

Fourth ve ntricle (lateral recess, torn)

PLATE 243B