Researchers describe a blind-ending tube lined on all sides by a pseudostratified epithelium and with associated submucosal glands. It seems highly likely that this structure is the adult human remnant of the vomeronasal organ (Johnson et al. 1994). The vomeronasal cavities were located at the base of the most anterior part of the nasal septum which can be detected by computed tomography. Histological studies indicated that the vomeronasal cavities consisted of a pit generally connected to a duct extending in a posterior direction under the nasal mucosa. Many glands were present around the duct, which contained mucus (Trotier et al. 2000). There are some conflicts about the description and identification of VNO, VNO pit, and VNO cavity. In some studies, researchers described the variates of nasopalatine fossa (NPF) and the nasopalatine recess (NPR). There are some questions about the endoscopic view of the vomeronasal pit. NPF and the NPR are discrete, but variable, structures found to be located adjacent to the VNO region. The NPF is not a vomeronasal pit. A septal mucosal pit could hide the vomeronasal duct opening. The VNO is a submucosal structure located 2–8 mm superior to the NPR and cannot be positively identified either macroscopically or endoscopically (Bhatnagar et al. 2002). However, in another study, the vomeronasal cavities were claimed to be observed by endoscopy in some adults, but they lacked sensory neurons and nerve fibers (Trotier 2011). A study on the human VNO revealed the following major results: (1) a VNO is detectable in approximately two-thirds of the population and bilateral VNOs are present in approximately 40 % of investigated subjects, (2) its localization on the left and right nasal septum is almost symmetrical, and (3) detectability of the VNO is not related to age or gender (Knecht et al. 2001).

The human VNO was found to be variable in form. The thickness of the epithelium was variable both medially and laterally and comprised tall cells with discontinuous cilia on their free surface (Kunwar et al. 2001). Human VNOs also varied in anteroposterior and superoinferior position relative to the anterior nasal spine and the nasal cavity floor (Smith et al. 2001).

The epithelium lining the human VNO is explained as unlike that of VNOs in other species and unlike that of olfactory or respiratory epithelium in humans. There are many elongated cells presenting a microvillar surface to the lumen of the organ but most are not similar to microvillar vomeronasal sensory organs (VSNs) of other species. They have not been shown to have axons leaving the epithelium nor to make synaptic contact with axons in the epithelium. Therefore, if these cells are chemosensitive, they have no obvious way of communication with the brain (Stensaas et al. 1991).

These unique elongated bipolar microvillar cells have been found to stain with several immunomarkers (Monti-Bloch, Jennings-White et al. 1998). The histology of the vomeronasal epithelium (VNE) appeared extremely heterogeneous. There were sections of stratified, respiratory, and typical pseudostratified vomeronasal epithelia consisting of slender bipolar cells. Mostly negative immunohistochemical results for OMP indicated that the human VNE does not function like the mature olfactory epithelium (Witt et al. 2002). These cells show physiological properties similar to chemosensory receptor cells of other mammalian species. And the presence of some bipolar cells positive for both protein gene product (PGP) 9.5 and soybean lectin pointed to a neuron-like activity of a small subset of VNE cells. Immunohistochemical localization of three molecular markers, neuron-specific enolase (NSE) and PGP 9.5 for neurons and neuroendocrine cells, and olfactory marker protein for olfactory receptor neurons was investigated in the VNE of adult humans. NSE and PGP 9.5 immunoreactive cells were identified in the VNE (Takami et al. 1993).

The VNOs of humans and chimpanzees had some structural similarities to nonhomologous ciliated gland ducts seen in other primates. However, certain distinctions from the VNOs of other primates or nonhomologous epithelial structures characterize the human/chimpanzee VNO: (1) bilateral epithelial tubes; (2) a superiorly displaced position in the same plane as the paraseptal cartilages; (3) a homogeneous, pseudostratified columnar morphology with ciliated regions; and (4) mucous-producing structures in the epithelium itself (Smith et al. 2002).