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Neuroanatomy Glossary |
This glossary contains information on the limbic system and related structures. Many of terms used below were discussed in atlas sections. Start by clicking on a letter in the table. You can also search the glossary in the following ways:
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Note: [TA] stands for Terminologia Anatomica - See TA entry below
: [Sted] indicates the definition is from Stedman's Dictionary
Amygdala - also called the amygdaloid complex. It isa large composite nucleus in the anterior temporal lobe beneath the uncus. It is an important part of the limbic lobe to which it has widespread connections. Its two main connecting tracts are the stria terminalis which is adjacent to the lateral ventricle and the ventral amygdalofugal pathway that lies in the substantia innominata in the basal forebrain.
Anterior nucleus of the thalamus - the thalamic nucleus to which the mammillothalamic tract projects from the mammillary body. It forms a prominence projecting into the third ventricle at the superior and anterior portion of the thalamus, the anterior thalamic tubercle.
Anterior perforated substance - a region of gray matter in the limbic system immediately posterior to the gyrus rectus. The name derives from the many holes created in this region by the penetrating lateral lenticulostriate arteries arising from the superior surface of the first part of the middle cerebral artery. It is part of the basal forebrain. A large portion of the gray matter is the olfactory nucleus or tubercle. See CT image 4 where the anterior perforated substance is labeled as the basal forebrain number 6.
Basal forebrain - an imprecisely defined region on the medial and ventral surface of the brain that lacks the organization typical of the cerebral cortex. It extends from the anterior perforated substance anteriorly to the hypothalamus caudally. Laterally it is continuous with the most anterior and inferior portion of the insular cortex. The point where the anterior inferior insular cortex becomes continuous with basal forebrain is called the limen insulae. See MR coronal images 5 and 6.
B
asal nucleus of Meynert - See Innominate substance.Caudate Nucleus: - an elongated mass of gray matter that is closely related to the lateral ventricle. Around the rostral border of the internal capsule, it is fused with the putamen of the lentiform nucleus while its tail terminates in close relationship to the amygdala
. It is one one of the parts of the striatum. The other is the putamen.Cerebral Peduncle - [Sted][TA]; originally denoting either of the two halves of the midbrain (a relatively narrow “neck” connecting the forebrain to the hindbrain); this term has been variably used to designate only those large bundles of corticofugal fibers forming the crus cerebri or to designate the crus cerebri plus the midbrain tegmentum; this latter, more inclusive, usage (crus cerebri and midbrain tegmentum) is preferred; the substantia nigra, while a part of the base of the peduncle (basis pedunculi), is considered a structure separating the midbrain tegmentum from the crus cerebri.
Fornix: - the major efferent fiber tract arising from the hippocampal formation. It is the direct continuation of the alveus and the fimbria. Below the splenium of the corpus callosum, these structures become the crus of the fornix. Under the body of the corpus callosum, the two crura fuse to become the body of the fornix which is attached to the corpus callosum superiorly by the septum pellucidum. Anteriorly, the body turns ventrally in front of the interventricular foramina and splits into right and left half. These vertical portions are referred to as the columns of the fornix. The main portion of the columns (postcommissural fornix) pass inferiorly through the hypothalamus and terminate in the mammillary bodies. A small portion of the columns (precommissural fornix) split off above the anterior commissure and terminate anteriorly in the septal nuclei.
Globus Pallidus - the more medial part of the lentiform nucleus. It is separated from the putamen by a thin layer of white matter called the lateral medullary lamina. It is considered the oldest part of the corpus striatum, and it receives its name from the fact that the many myelinated fibers that traverse its structure give it a lighter color than that of the putamen or caudate nucleus.
Innominate
substance - [Sted][TA]; the region of the forebrain that lies ventral to the
anterior half or so of the lentiform nucleus, extending in the frontal plane
from the lateral preopticohypothalamic zone laterally over the optic tract to
the amygdala (amygdaloid body); rostrally it tapers off over the dorsal border
of the olfactory tubercle, caudally it ends where the internal capsule reaches
the surface to form the cerebral peduncle or pes pedunculi. Notable among its
polymorphic cell population is the large-celled basal nucleus of Meynert. These
magnocellular elements within the i. substantia are present in the medial septum
and the diagonal band of Broca, but occur in largest numbers ventral to the
globus pallidus. Histochemical evidence indicates that magnocellular elements
distribute cholinergic fibers widely in the cerebral cortex and that these cells
undergo selective degeneration in Alzheimer disease. Syn: substantia innominata
[TA].
Limen insulae - [Sted][TA]; the band of transition between the anterior portion of the gray matter of the insula and the anterior perforated substance; it is formed by a narrow strip of olfactory cortex along the lateral side of the lateral olfactory stria. See answer for question 1 in the Self Test section for further discussion.
Mammillary Body - [Sted][TA]; a small, round, paired cell group that protrudes into the interpeduncular fossa from the inferior aspect of the hypothalamus. It receives hippocampal fibers through the fornix and projects fibers to the anterior thalamic nuclei and into the brainstem tegmentum.
Paraterminal Gyrus - See Subcallosal gyrus.
Putamen is the largest part of the basal ganglia and its most rostral part is located lateral to the head of the caudate nucleus, being separated by the anterior part of the internal capsule. It is the larger part of the lentiform nucleus which is comprised of the putamen and globus pallidus.
Subcallosal Area - See Subcallosal Gyrus.
Subcallosal Gyrus - [Sted][TA] a slender vertical whitish band immediately anterior to the lamina terminalis and anterior commissure; contrary to its name, it is not a cortical convolution but is the ventral continuation of the transparent septum. The small ridge of tissue immediately rostral to the lamina terminalis is sometimes designated as a separate part of the subcallosal area and called the paraterminal gyrus. (For a discussion on the subcallosal gyrus and the medial frontal lobe region below the corpus callosum, see question 2 in the Self Test).
Substantia innominata - See Innominate substance.
TA - See Terminologia Anatomica
Terminologia Anatomica [TA] [Sted]
A system of anatomic nomenclature, consisting of about 7500 terms, devised and
approved by the International Federation of Associations of Anatomists (IFAA)
and promulgated in August, 1997, at São Paulo, Brazil.
Since its foundation in 1903 the IFAA has held periodic conventions for the
standardization of anatomic concepts and terminology. In 1989 the federation
elected a 12-member Federative Committee on Anatomical Terminology (FCAT),
consisting of experts from 11 countries, to undertake a wholesale revision of
the last (sixth) edition of Nomina Anatomica (NA VI). With the election of
additional members in 1994, the FCAT had representatives from 16 countries and 5
continents. The committee solicited suggestions from anatomists and others
around the world, and from more than 10,000 terms proposed for introduction or
retention, they formulated and published a list of those deemed worthy of
consideration. During 8 years of deliberations they chose the simplest and most
exact terms, preferring those that are descriptive of form or function over
semantically opaque ones. Some 10% of formerly accepted terms were rejected or
altered because they were considered inaccurate, ambiguous, or otherwise
unsuitable. About 1000 new terms were introduced, including some for structures
not officially named in earlier nomenclatural systems. Many of these terms had
already been adopted informally in various countries. Adoption of the new
terminology is expected to be widespread. Because English is spoken in many
countries and serves as a common language for scientific and medical
communication, English equivalents of Latin terms are given in the published
version of TA. However, only the Latin terms have official status. The FCAT is
currently working on complementary formulations of histologic, cytologic,
embryologic, dental, and anthropologic terminology.
Uncinate fasciculus - [Sted][TA]; a band of long association fibers reciprocally connecting the frontal and temporal lobes of the cerebrum, running caudally through the white matter of the frontal lobe, sharply curving ventrally under the stem of the sylvian fissure, and then fanning out to the cortex of the anterior half of the superior and middle temporal gyri.
Uncus - a prominent bulge on the medial surface of the temporal lobe. The bulge contains the medial portion of two structures: anteriorly the amygdala and posteriorly the pes hippocampi. These structure are separated by the most anterior portion of the temporal horn of the lateral ventricle which is lies horizontally in a coronal plane. The uncus is part of the parahippocampal gyrus.