Olfactory tract

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Olfactory peduncle
Cerebral Gyri - Inferior Surface2.png
Olfactory peduncle lying in olfactory sulcus and olfactory striae labelled
Details
System Olfactory system
Location Brain
Identifiers
Latin tractus olfactorius
NeuroNames 283
NeuroLex ID birnlex_1663
TA98 A14.1.09.431
TA2 5539
FMA 77626
Anatomical terms of neuroanatomy

The olfactory peduncle (olfactory tract, olfactory stalk) is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex. It is a narrow white band, triangular on coronal section, the apex being directed upward.

Contents

The term olfactory tract is a misnomer, as the olfactory peduncle is actually made up of the juxtaposition of two tracts, the medial olfactory tract (giving the medial and intermediate olfactory stria) and the lateral olfactory tract (giving the lateral and intermediate olfactory stria). [1] However, the existence of the medial olfactory tract (and consequently the medial stria) is controversial in primates (including humans). [2]

Structure

The olfactory peduncle and olfactory bulb lie in the olfactory sulcus [3] a sulcus formed by the medial orbital gyrus on the inferior surface of each frontal lobe. The olfactory peduncles lie in the sulci which run closely parallel to the midline. Fibers of the olfactory peduncle appear to end in the antero-lateral part of the olfactory tubercle, the dorsal and external parts of the anterior olfactory nucleus, the frontal and temporal parts of the prepyriform area, the cortico-medial group of amygdala nuclei and the nucleus of the stria terminalis. [4]

The olfactory peduncle divides posteriorly into three main branches: the medial, intermediate and lateral striae. The olfactory peduncle thus terminates in a triangular structure called the olfactory trigone. Caudal to these elements is the anterior perforated substance, the anterior part of which is marked by the relief of the olfactory tubercle. Finally, projections from the olfactory peduncle to the anterior olfactory nucleus are sometimes grouped together under the name of superior olfactory stria. [1]

The terms olfactory tubercle and olfactory trigone are commonly confused in the literature.

Medial olfactory stria

The medial olfactory stria is classically described as running medially behind the parolfactory area (hence its name) and terminating in the subcallosal gyrus.

However, this description has been rejected for some fifty years. [2] The medial olfactory stria is now described as terminating much more medially, in the ventral taenia tecta. [1]

Intermediate olfactory stria

The intermediate olfactory stria is the branch (or branches) extending from the medial or lateral olfactory striae to the olfactory tubercle and anterior perforated substance. Trolard's term "pectineal formation " is used to refer to multiple intermediate striae extending from the lateral olfactory stria. [1]

Lateral olfactory stria

The lateral olfactory stria is directed across the lateral part of the anterior perforated substance and then bends abruptly medially toward the uncus of the parahippocampal gyrus.

Clinical significance

Destruction to the olfactory peduncle results in ipsilateral anosmia (loss of the ability to smell). Anosmia either total or partial is a symptom of Kallmann syndrome a genetic disorder that results in disruption of the development of the olfactory peduncle. [5] [6] The depth of the olfactory sulcus is an indicator of such congenital anosmia. [7]

Additional images

Related Research Articles

Articles related to anatomy include:

<span class="mw-page-title-main">Brainstem</span> Posterior part of the brain, adjoining and structurally continuous

The brainstem is the stalk-like part of the brain that interconnects the cerebrum and diencephalon with the spinal cord. In the human brain, the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch.

<span class="mw-page-title-main">Rhinencephalon</span>

In animal anatomy, the rhinencephalon, also called the smell-brain or olfactory brain, is a part of the brain involved with smell. It forms the paleocortex and is rudimentary in the human brain.

<span class="mw-page-title-main">Internal capsule</span> White matter structure situated in the inferomedial part of each cerebral hemisphere of the brain

The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.

<span class="mw-page-title-main">Olfactory system</span> Sensory system used for smelling

The olfactory system or sense of smell is the sensory system used for smelling (olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli.

<span class="mw-page-title-main">Fourth ventricle</span> One of four central brain cavities filled with cerebrospinal fluid

The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle. The fourth ventricle extends from the cerebral aqueduct to the obex, and is filled with cerebrospinal fluid (CSF).

<span class="mw-page-title-main">Lateral ventricles</span> Two largest ventricles in each cerebral hemisphere

The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid. Each cerebral hemisphere contains a lateral ventricle, known as the left or right lateral ventricle, respectively.

<span class="mw-page-title-main">Middle cerebral artery</span> Paired artery that supplies blood to the cerebrum

The middle cerebral artery (MCA) is one of the three major paired cerebral arteries that supply blood to the cerebrum. The MCA arises from the internal carotid artery and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex. It also supplies blood to the anterior temporal lobes and the insular cortices.

<span class="mw-page-title-main">Lobes of the brain</span> Parts of the cerebrum

The lobes of the brain are the major identifiable zones of the human cerebral cortex, and they comprise the surface of each hemisphere of the cerebrum. The two hemispheres are roughly symmetrical in structure, and are connected by the corpus callosum. They traditionally have been divided into four lobes, but are today considered as having six lobes each. The lobes are large areas that are anatomically distinguishable, and are also functionally distinct to some degree. Each lobe of the brain has numerous ridges, or gyri, and furrows, the sulci that constitute further subzones of the cortex. The expression "lobes of the brain" usually refers only to those of the cerebrum, not to the distinct areas of the cerebellum.

<span class="mw-page-title-main">Posterior cerebral artery</span> Artery which supplies blood to the occipital lobe of the brain

The posterior cerebral artery (PCA) is one of a pair of cerebral arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.

<span class="mw-page-title-main">Rhomboid fossa</span> Depression in the human brain

The rhomboid fossa is a rhombus-shaped depression that is the anterior part of the fourth ventricle. Its anterior wall, formed by the back of the pons and the medulla oblongata, constitutes the floor of the fourth ventricle.

<span class="mw-page-title-main">Diagonal band of Broca</span>

The diagonal band of Broca interconnects the amygdala and the septal area. It is one of the olfactory structures. It is situated upon the inferior aspect of the brain. It forms the medial margin of the anterior perforated substance.

The amygdalofugal pathway is one of the three major efferent pathways of the amygdala, meaning that it is one of the three principal pathways by which fibers leave the amygdala. It leads from the basolateral nucleus and central nucleus of the amygdala. The amygdala is a limbic structure in the medial temporal lobe of the brain. The other main efferent pathways from the amygdala are the stria terminalis and anterior commissure.

<span class="mw-page-title-main">Subcallosal area</span>

The subcallosal area is a small triangular field on the medial surface of the hemisphere in front of the subcallosal gyrus, from which it is separated by the posterior parolfactory sulcus; it is continuous below with the olfactory trigone, and above and in front with the cingulate gyrus; it is limited anteriorly by the anterior parolfactory sulcus.

<span class="mw-page-title-main">Anterior perforated substance</span> Part of the brain

The anterior perforated substance is a part of the brain. It is bilateral. It is irregular and quadrilateral. It lies in front of the optic tract and behind the olfactory trigone.

<span class="mw-page-title-main">Basal vein</span>

The basal vein is a vein in the brain. It is formed at the anterior perforated substance by the union of

<span class="mw-page-title-main">Stria medullaris of thalamus</span>

The stria medullaris (SM), is a part of the epithalamus and forms a bilateral white matter tract of the initial segment of the dorsal diencephalic conduction system (DDCS). It contains afferent fibers from the septal nuclei, lateral preoptico-hypothalamic region, and anterior thalamic nuclei to the habenula. It forms a horizontal ridge on the medial surface of the thalamus on the border between dorsal and medial surfaces of thalamus. The SM, in conjunction with the habenula and the habenular commissure, forms the habenular trigone. It is considered to be the primary afferent of the DDCS.

<span class="mw-page-title-main">Paleocortex</span> Region within the telencephalon in the vertebrate brain

In anatomy of animals, the paleocortex, or paleopallium, is a region within the telencephalon in the vertebrate brain. This type of cortical tissue consists of three cortical laminae. In comparison, the neocortex has six layers and the archicortex has three or four layers. Because the number of laminae that compose a type of cortical tissue seems to be directly proportional to both the information-processing capabilities of that tissue and its phylogenetic age, paleocortex is thought to be an intermediate between the archicortex and the neocortex in both aspects.

<span class="mw-page-title-main">Orbital gyri</span>

The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone. It is divided into four orbital gyri by a well-marked H-shaped orbital sulcus. These are named, from their position, the medial, anterior, lateral, and posterior, orbital gyri. The medial orbital gyrus presents a well-marked antero-posterior sulcus, the olfactory sulcus, for the olfactory tract; the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.

References

  1. 1 2 3 4 De Cannière, Gilles (January 2024). "The olfactory striae: A historical perspective on the inconsistent anatomy of the bulbar projections". Journal of Anatomy. 244 (1): 170–183. doi:10.1111/joa.13952. ISSN   0021-8782. PMC   10734660 . PMID   37712100.
  2. 1 2 Stumpf, W.E.; Grant, L.D., eds. (1976-07-23). "Olfactory Projections to the Diencephalon". Anatomical Neuroendocrinology: Based on the International Conference on Neurobiology of CNS-Hormone Interactions, Chapel Hill, N.C., May 1974. S. Karger AG. pp. 30–39. doi:10.1159/000398021. ISBN   978-3-8055-2154-3.
  3. Carpenter, Malcolm B. (1985). Core text of neuroanatomy (3rd ed.). Baltimore: Williams & Wilkins. p. 29. ISBN   0683014552.
  4. Allison, A. C. (October 1954). "The secondary olfactory areas in the human brain". Journal of Anatomy. 88 (4): 481–488. ISSN   0021-8782. PMC   1244658 . PMID   13211468.
  5. Purves, Dale (2012). Neuroscience (5th ed.). Sunderland, Mass. p. 515. ISBN   9780878936953.{{cite book}}: CS1 maint: location missing publisher (link)
  6. "Kallmann syndrome". Genetics Home Reference. US Library of Medicine. National Institutes for Health. Genetic and Rare Diseases Information. June 26, 2016. Retrieved November 15, 2021.
  7. Huart, C.; Meusel, T.; Gerber, J.; Duprez, T.; Rombaux, P.; Hummel, T. (November 2011). "The Depth of the Olfactory Sulcus Is an Indicator of Congenital Anosmia". American Journal of Neuroradiology. 32 (10): 1911–1914. doi: 10.3174/ajnr.A2632 . PMC   7966015 . PMID   21868619.

PD-icon.svgThis article incorporates text in the public domain from page 826 of the 20th edition of Gray's Anatomy (1918)