Special Histology and Embryology: Practical Course - V. K. Napkhanyuk 2001
Sense Organs
Organ of Smell
The Organ of smell (organum olfactorium) is an analyzer whose peripheral part is a specialized area of the mucous membrane within the olfactory region. In humans, this area covers the superior and partially the middle nasal conchae, as well as the upper part of the nasal septum.
Externally, the olfactory region is distinguished from the respiratory part by its yellowish color.
The olfactory zone is formed by an epithelium-like layer 60-90 µm thick, which consists of the following Cell types:
a) olfactory neurosensory Cells (cellulae neurosensoriae olfactoriae), which possess a short peripheral process—the dendrite—and a long central process—the axon; their perikarya (cell bodies containing the nuclei) are typically located in the Middle layer of the olfactory epithelium. The distal ends of the peripheral processes terminate in characteristic swellings known as olfactory clubs (clavae olfactoriae), bearing 10-12 tapered, motile olfactory cilia at their apex (micrographs 4, 5);
b) supporting sustentacular epitheliocytes (epitheliocyta sustentas), which form a multi-row epithelial layer interspersed with olfactory cells separated by these supporting elements. The apical surface of these epitheliocytes features numerous microvilli about 4 µm long. These cells exhibit signs of apocrine secretion and possess a High Metabolic Rate;
c) basal epitheliocytes (epitheliocyta basales), resting on the basement membrane; they feature cytoplasmic extensions that surround bundles of the central processes of the olfactory cells. It is hypothesized that basal epitheliocytes serve as a source for the regeneration of receptor cells.
In the underlying loose Fibrous Connective Tissue of the olfactory region lie the terminal secretory portions of tubuloalveolar glands, which produce a secretion containing mucopolysaccharides. This secretion, combined with the product of the supporting epitheliocytes, moistens The surface of the olfactory zone—a prerequisite for the proper functioning of olfactory cells. Odorous substances dissolve in this fluid film bathing the olfactory cilia, allowing them to be detected by receptor Proteins embedded in the ciliary membrane of the olfactory cells.
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Fig. 8. Cross-section of the mucosa of the nasal olfactory region. Hematoxylin and eosin stain. x 400:
1 — olfactory epithelium (a — cuticle and olfactory hairs; b — nuclei of olfactory cells); 2 — supporting cell; 3 — olfactory glands; 4 — Blood vessel; 5 — fibrous connective tissue
Slides for Examination
Slide 1. Cross-section of the mucosa of the nasal olfactory region (Fig. 8).
Low magnification. Examine the slide.
Identify the epithelium-like layer composed of three cell types: olfactory neurosensory cells, supporting epitheliocytes, and basal epitheliocytes. Glands are located within the lamina propria.
High magnification. Note the arrangement of the nuclei of the olfactory and supporting cells. In the olfactory cells, nuclei occupy a mid-level position; the underlying loose fibrous layer contains tubuloalveolar olfactory glands.
Label on the drawing: 1) olfactory epithelium (cuticle and olfactory hairs; nuclei of olfactory cells); 2) supporting cell; 3) olfactory glands; 4) blood vessel; 5) fibrous connective tissue.
Electron micrograph 4. Epithelium of the nasal olfactory mucosa. x 3000:
1 — olfactory cells; 2 — club-shaped endings of olfactory cells; 3 — supporting cells; 4 — microvilli (adapted from Rodin's atlas)
Electron micrograph 5. Peripheral process of olfactory cells. X 60,000:
1 — peripheral process of the olfactory cell; 2 — olfactory club; 3 — olfactory hairs; 4 — basal bodies; 5 — Mitochondria; 6 — vacuoles; 7 — supporting cells; 8 — desmosomes (after A. A. Bronshtein and G. A. Pyatkina)
1. Development of the Olfactory Organ.
2. Structure OF THE receptor neurosensory olfactory cells.
3. Structure of supporting epithelial cells.
4. Structure of basal epithelial cells.
5. Age-related Changes in the epithelium of the olfactory region of the Nasal cavity.
6. Degeneration of the epithelium of the olfactory region of the nasal mucosa.
Case studies
1. If the mucous membrane of the upper part of the middle nasal concha is damaged, the peripheral part of which analyzer will be destroyed?
Sample exam questions
1. Development, structure, and histophysiology of the olfactory organ.
Last update: 10/08/2026
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