Page 212 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Nervous System / 197

prosencephalon further subdivides to form Telencephalon. The telencephalon, or
the telencephalon (future cerebrum) and
VetBooks.ir the diencephalon, and the rhombencepha- cerebrum, comprises the two cerebral
hemispheres, including the cerebral
cortex, the basal nuclei and other
lon divides into the metencephalon (future
pons and cerebellum) and the myelenceph- subcortical nuclei, and an aggregate of
alon (future medulla oblongata). The mes- functionally related structures called the
encephalon does not subdivide; it will rhinencephalon. The telencephalon
become the future midbrain (often persis- encloses the cavities of the lateral ventricles.
tently called the mesencephalon). The surface area of the cerebrum in
domestic mammals is increased by numer-
ous infoldings that form convex ridges,
Central Nervous System called gyri (singular gyrus), which are sep-
arated by furrows called fissures or sulci
Brain (singular sulcus). A particularly prominent
fissure, the longitudinal fissure, lies on
The gross subdivisions of the adult brain the median plane and separates the cere-
include the cerebrum, cerebellum, and brum into its right and left hemispheres.
brainstem (Figs. 10‐8 and 10‐9). The cere- Unlike the spinal cord, in the cerebrum
brum develops from the embryonic telen- most of the neuronal cell bodies (i.e., the
cephalon. The components of the brainstem gray matter) are on the exterior. This layer
are defined in a number of ways; for our of cerebral gray matter is called cerebral
purposes, we include the diencephalon, cortex (plural: cortices). In humans and
midbrain, pons, and medulla oblongata some animals, the cortical areas have been
as parts of the brainstem. extensively mapped to localize specific

(A)
Cerebrum

Cerebellum

Brainstem

Transverse fissure (C)
Cerebrum
Right hemisphere
(B)

Longitudinal
fissure

Left hemisphere
Brainstem
Figure 10-8. Subdivisions of the brain. (A) Left lateral view. (B) Dorsal view. The cerebrum consists of
right and left cerebral hemispheres. (C) Dorsal view of brainstem with cerebrum and cerebellum removed.