The olfactory tract is a

bilateral Bilateral may refer to any concept including two sides, in particular: *Bilateria, bilateral animals *Bilateralism, the political and cultural relations between two states *Bilateral, occurring on both sides of an organism ( Anatomical terms of l ...

bundle of afferent nerve fibers from the

mitral The mitral valve (), also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two cusps or flaps and lies between the left atrium and the left ventricle of the heart. The heart valves are all one-w ...

and

tufted cells Tufted cells are found within the olfactory glomeruli. They receive input from the receptor cells of the olfactory epithelium found in areas of the nose able to sense smell. Both tufted cells and mitral cells are called projection neurons. Project ...

of the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex ( ...

that connects to several target regions in the brain, including the

piriform cortex The piriform cortex, or pyriform cortex, is a region in the brain, part of the rhinencephalon situated in the cerebrum. The function of the piriform cortex relates to the sense of smell. Structure The piriform cortex is part of the rhinencepha ...

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verte ...

, and

entorhinal cortex The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.Integrating time from experience in the ...

. It is a narrow white band, triangular on

coronal section The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes. Details The coronal plane is an example of a longi ...

, the apex being directed upward.

Structure

The olfactory tract and

lie in the olfactory sulcus a sulcus formed by the medial orbital gyrus on the inferior surface of each

frontal lobe The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove be ...

. The olfactory tracts lie in the sulci which run closely parallel to the midline. Fibers of the olfactory tract appear to end in the antero-lateral part of the

olfactory tubercle The olfactory tubercle (OT), also known as the tuberculum olfactorium, is a multi-sensory processing center that is contained within the olfactory cortex and ventral striatum and plays a role in reward cognition. The OT has also been shown to ...

, the dorsal and external parts of the

anterior olfactory nucleus The anterior olfactory nucleus (AON; also called the anterior olfactory cortex) is a portion of the forebrain of vertebrates. It is involved in olfaction and has supposedly strong influence on other olfactory areas like the olfactory bulb and the ...

, the frontal and temporal parts of the

prepyriform area Prepyriform area (or prepiriform cortex) is a portion of the rhinencephalon consisting of paleocortex. Some sources state that it is part of the primary olfactory cortex The primary olfactory cortex (POC) is a portion of the cerebral cortex. ...

, the cortico-medial group of amygdala nuclei and the nucleus of the stria terminalis. The olfactory tract divides posteriorly into a medial and a lateral stria. Caudal to this is the

olfactory trigone The olfactory trigone is a small triangular area in front of the anterior perforated substance. Its apex, directed forward, occupies the posterior part of the olfactory sulcus, and is brought into view by throwing back the olfactory tract. It is ...

, and the anterior perforated substance.

Medial olfactory stria

The medial olfactory stria turns medially behind the

parolfactory area The subcallosal area (parolfactory area of Broca) 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 t ...

and ends in the

subcallosal gyrus The subcallosal gyrus (paraterminal gyrus, peduncle of the corpus callosum) is a narrow lamina on the medial surface of the hemisphere in front of the lamina terminalis, behind the parolfactory area, and below the rostrum of the corpus callosum. I ...

; in some cases a small ''intermediate stria'' is seen running backward to the anterior perforated substance.

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 The uncus is an anterior extremity of the parahippocampal gyrus. It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis (also called rhinal sulcus). Although superficially continuous with the hippo ...

of the

parahippocampal gyrus The parahippocampal gyrus (or hippocampal gyrus') is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system. The region plays an important role in memory encoding and retrieval. It has been in ...

Clinical significance

Destruction to the olfactory tract results in ipsilateral

anosmia Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia, which is a decreased sensitivity to some or all smells. Anosmia can be due to a nu ...

(loss of the ability to smell). Anosmia either total or partial is a symptom of

Kallmann syndrome Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty. Kallmann syndrome is a form of a group of conditions termed hypogonadotropic hypogonadism. To distinguish it from other forms of hypog ...

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

that results in disruption of the development of the olfactory tract. The depth of the olfactory sulcus is an indicator of such congenital anosmia.

Additional images

File:Gray732.png, Scheme of

rhinencephalon In animal anatomy, the rhinencephalon (from the Greek, ῥίς, ''rhis'' = "nose", and ἐγκέφαλος, ''enkephalos'' = "brain"), also called the smell-brain or olfactory brain, is a part of the brain involved with smell (i.e. olfaction). ...

. (Olfactory tract visible at left.) File:Gray724.png, Base of brain. File:Gray772.png, Plan of olfactory neurons. File:Gray729 olfactory sulcus.png, Orbital surface of frontal lobe olfactory sulcus shown in red.

References

External links

* {{Authority control Olfactory system