Location and Structure
The vomeronasal organ (VNO) is located in the anterior nasal septum, near the junction of cartilage and bone. In humans, it appears as a small pit or cavity that can sometimes be visualized with nasal endoscopy.
Anatomical Position
| Feature | Description |
|---|---|
| Location | Nasal septum, 2cm from nostril opening |
| Appearance | Small pit or blind pouch |
| Size | 2-8mm in length when present |
| Opening | Vomeronasal duct opening to nasal cavity |
Detection Methods
The presence of VNO structures in humans has been confirmed through multiple methods:
- Nasal endoscopy — Direct visualization of VNO pit
- MRI and CT scans — Imaging of nasal structures
- Histological examination — Microscopic analysis of tissue
- Electron microscopy — Ultrastructural analysis
Prevalence in Humans
Studies report varying rates of VNO presence:
| Population | VNO Present | Study Notes |
|---|---|---|
| Infants | ~100% | Regresses during development |
| Children | ~80% | More common in younger ages |
| Adults | 30-70% | Varies by study methodology |
Why the Variation?
The wide range in reported prevalence likely reflects:
- Different detection methods (endoscopy vs. histology)
- Age of subjects studied
- Definition of “presence” (pit vs. functional structure)
- Population differences
Embryonic Development
During fetal development, the VNO follows a specific pattern:
Timeline
- Week 5-6 — VNO primordium appears
- Week 7-8 — VNO cavity forms, neurons develop
- Week 9-14 — Neural connections to brain form
- Week 14+ — Regression begins
Critical Role in Development
Even though the VNO may not function in adults, it plays a crucial embryonic role:
GnRH-secreting neurons originate in the olfactory placode and migrate along the VNO/terminal nerve pathway to reach the hypothalamus. This migration is essential for puberty and reproductive function.
This is why VNO abnormalities during development can cause Kallmann syndrome — a condition causing absent puberty due to failed GnRH neuron migration.
Comparison to Other Mammals
Functional Mammalian VNO
In species with working VNOs (mice, rats, hamsters):
| Component | Status |
|---|---|
| Sensory neurons | Present, functional |
| V1R/V2R receptors | Expressed, functional |
| Neural connections | Connected to accessory olfactory bulb |
| TRPC2 channel | Functional ion channel |
Human VNO
| Component | Status |
|---|---|
| Sensory neurons | Absent in adults |
| V1R/V2R receptors | Pseudogenes (non-functional) |
| Neural connections | Not present in adults |
| TRPC2 channel | Pseudogene |
Histological Findings
Microscopic examination of adult human VNO tissue reveals:
What’s Present
- Ciliated respiratory epithelium
- Blood vessels
- Small nerves (sensory function unclear)
- Mucous glands
What’s Missing
- Bipolar sensory neurons (like in functional VNOs)
- Specialized receptor cells
- Clear neural connections to brain
The “Vomeronasal Pit”
What remains in adults is often called the vomeronasal pit or organ of Jacobson — a small blind-ended tube that:
- Opens into the nasal cavity
- Contains non-sensory epithelium
- Has no demonstrated sensory function
- May be a vestigial remnant
Clinical Significance
Surgical Considerations
Surgeons operating on the nasal septum should be aware of VNO location to:
- Avoid unnecessary damage
- Preserve potentially functional tissue
- Understand patient anatomy
Research Interest
The VNO remains of interest for:
- Understanding pheromone detection evolution
- Potential drug delivery routes
- Studying chemosensory development
Key Points
- The VNO is anatomically present in many adult humans
- It appears as a small pit in the nasal septum
- Prevalence decreases from infancy to adulthood
- Adult VNO lacks the sensory neurons found in functional mammalian VNOs
- The VNO plays a critical developmental role even if non-functional in adults
- Its presence doesn’t prove function — structure ≠ function
References
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Johnson A, et al. “Ultrastructure of the human vomeronasal organ.” J Submicrosc Cytol Pathol. 1991;23(1):67-79.
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Stoyanov GS, et al. “The clinical significance of the human vomeronasal organ.” Cureus. 2023;15(3):e36738.
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Trotier D. “Vomeronasal organ and human pheromones.” Eur Ann Otorhinolaryngol Head Neck Dis. 2011;128(4):184-90.