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Related Concept Videos

Olfactory Receptors: Location and Structure01:03

Olfactory Receptors: Location and Structure

The process of olfaction, also known as the sense of smell, is a sophisticated chemical response system. The specialized sensory neurons that facilitate this process, known as olfactory receptor neurons, are situated in an upper segment of the nasal cavity, known as the olfactory epithelium. Olfactory sensory neurons are bipolar, with their dendrites extending from the epithelium's apex into the mucus that lines the nasal cavity. Airborne molecules, when inhaled, traverse the olfactory...
Physiology of Smell and Olfactory Pathway01:20

Physiology of Smell and Olfactory Pathway

Humans detect odors with the help of specialized cells located in the upper part of the nasal cavity, called olfactory receptor neurons (ORNs). ORNs possess hair-like structures called cilia, which are receptive to sensations from the inhaled air. When an odorant molecule binds to a specific receptor on the cell of the cilia, it leads to a series of events that ultimately cause the ORN to send electrical signals to the olfactory bulb in the brain through the olfactory nerves.
The olfactory...
Olfaction01:25

Olfaction

The sense of smell is achieved through the activities of the olfactory system. It starts when an airborne odorant enters the nasal cavity and reaches olfactory epithelium (OE). The OE is protected by a thin layer of mucus, which also serves the purpose of dissolving more complex compounds into simpler chemical odorants. The size of the OE and the density of sensory neurons varies among species; in humans, the OE is only about 9-10 cm2.
The olfactory receptors are embedded in the cilia of the...
COPD: Pathogenesis and Clinical Features01:20

COPD: Pathogenesis and Clinical Features

Chronic obstructive pulmonary disease (COPD) is a group of lung conditions that progressively worsen over time, including chronic bronchitis and emphysema. This cluster of diseases collectively leads to a gradual and irreversible decline in lung function over time.
The primary cause for the onset of COPD is cigarette smoking and exposure to air pollution. These hazardous factors initiate a chain reaction within the lungs, resulting in chronic inflammation, damage to the airways, and a...

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Related Experiment Video

Updated: May 20, 2026

High-Speed Human Temporal Bone Sectioning for the Assessment of COVID-19-Associated Middle Ear Pathology
03:42

High-Speed Human Temporal Bone Sectioning for the Assessment of COVID-19-Associated Middle Ear Pathology

Published on: May 18, 2022

Histopathological changes in the olfactory pathway in COVID-19: An autopsy-based case-control study.

Mehmet Doğan1, Aytül Buğra2, Duygu Kırkık3,4

  • 1Council of Forensic Medicine, Ministry of Justice, Republic of Türkiye, İstanbul, Türkiye. drmehmetdoganmd@gmail.com.

Irish Journal of Medical Science
|May 19, 2026
PubMed
Summary

Neuropathological examination of COVID-19 decedents revealed reactive and vascular changes in the central nervous system, not direct viral infection. These findings suggest indirect mechanisms contribute to neurological symptoms in coronavirus disease 2019.

Keywords:
AnosmiaCOVID-19GliosisMicroglial activationNeuropathologyOlfactory systemSARS-CoV-2

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Studying the Effects of Inhaled Environmental Pollutants on Olfactory Function in Mice
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Studying the Effects of Inhaled Environmental Pollutants on Olfactory Function in Mice

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Studying the Effects of Inhaled Environmental Pollutants on Olfactory Function in Mice
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Published on: September 13, 2024

Area of Science:

  • Neuropathology
  • Central Nervous System (CNS) Disorders
  • Infectious Disease Pathology

Background:

  • Coronavirus disease 2019 (COVID-19) often presents with neurological symptoms like anosmia, prompting investigation into central nervous system (CNS) involvement.
  • Previous neuropathological studies on COVID-19 have yielded inconsistent results, with debate on direct viral effects versus indirect systemic responses.

Purpose of the Study:

  • To investigate neuropathological changes in the CNS of COVID-19 decedents.
  • To differentiate between direct viral effects and indirect mechanisms contributing to CNS alterations in COVID-19.

Main Methods:

  • An autopsy-based case-control study comparing 16 COVID-19-positive decedents with 15 age- and sex-matched controls.
  • Histopathological analysis of the olfactory bulb, olfactory tract, and frontal cortex, assessing reactive gliosis, microglial activation, inflammation, and vascular injury.

Main Results:

  • COVID-19 cases showed increased reactive gliosis and microglial activation in the olfactory bulb and mild perivascular inflammation in the frontal cortex.
  • No direct viral cytopathic changes or encephalitis were identified; systemic findings indicated severe multisystem disease.
  • Corpora amylacea and petechial hemorrhages were common in both groups, indicating nonspecific changes.

Conclusions:

  • COVID-19 is linked to CNS alterations characterized by reactive and vascular changes, not direct encephalitic processes.
  • The study highlights that many reported histological findings are nonspecific background changes.
  • Findings support indirect, reactive, and vascular mechanisms as primary drivers of CNS involvement in COVID-19.