400
UNIT THREE
4.
Occipital lobe.
The occipital lobe forms the posterior
portion of each cerebral hemisphere and is separated
from the cerebellum by a shelfl
ike extension of dura
mater called the
tentorium cerebelli.
The occipital lobe
and the parietal and temporal lobes have no distinct
boundary.
5.
Insula.
The insula (island of Reil) is a lobe deep within
the lateral sulcus and is so named because it is covered
by parts of the frontal, parietal, and temporal lobes. A
circular sulcus
separates the insula from the other lobes.
A thin layer of gray matter (2 to 5 millimeters thick)
called the
cerebral cortex
(ser
e
˘-bral kor
teks) constitutes
the outermost portion of the cerebrum. It covers the gyri,
dipping into the sulci and F ssures. The cerebral cortex con-
tains nearly 75% of all the neuron cell bodies in the nervous
system.
Just beneath the cerebral cortex is a mass of white mat-
ter that makes up the bulk of the cerebrum. This mass con-
tains bundles of myelinated nerve F
bers that connect neuron
cell bodies of the cortex with other parts of the nervous sys-
tem. Some of these F bers pass from one cerebral hemisphere
to the other by way of the corpus callosum, and others carry
TABLE
11.4
|
Structural Development
of the Brain
Embryonic Vesicle
Spaces Produced
Regions of the
Brain Produced
Forebrain
(prosencephalon)
± ±Anterior±portion±
(telencephalon)
Lateral ventricles
Cerebrum
Basal nuclei
± ±Posterior±portion±
(diencephalon)
Third ventricle
Thalamus
Hypothalamus
Posterior pituitary gland
Pineal gland
Midbrain
(mesencephalon)
Cerebral aqueduct
Midbrain
Hindbrain
(rhombencephalon)
± ±Anterior±portion±
(metencephalon)
Fourth ventricle
Cerebellum, pons
± ±Posterior±portion±
(myelencephalon)
Fourth ventricle
Medulla oblongata
Central sulcus
Gyrus
Sulcus
Frontal lobe
Lateral sulcus
Parietal lobe
Occipital lobe
Transverse
fissure
Cerebellar
hemisphere
Central sulcus
Longitudinal
fissure
Parietal lobe
Occipital lobe
Temporal lobe
(a)
(b)
(c)
Parietal lobe
Central sulcus
Occipital lobe
Frontal lobe
Insula
Retracted
temporal lobe
FIGURE 11.16
Colors in this f
gure distinguish the lobes o² the cerebral hemispheres. (
a
) Lateral view o² the le²t hemisphere. (
b
) Hemispheres
viewed ²rom above. (
c
) Lateral view o² the le²t hemisphere with the insula exposed.
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