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Barral J-P, Croibier A (2009) Olfactory nerve. Manual Therapy for the Cranial Nerves. Amsterdam: Elsevier.
PRESENTATION
The terminal nerves are a specialized bundle of nerves within the olfactory tracts. It arises from a bulge of the olfactory bulb called the accessory olfactory bulb, passes through the cribriform plate, and descends obliquely in an anterior and caudal direction on the partition. It ends up at the vomeronasal organ (organ of Jacobson1), a 2–7 mm conduit situated a short distance from the opening of the nostrils, on the anterocaudal aspect of the septum (Fig. 10.5).
The vomeronasal organ is a diverticulum of the olfactory organ. It is an isolated part of the sensory epithelium made up of typical olfactory cells.
Roughly speaking, the vomeronasal is a small circular or oval depression on the anterior part of the septal cartilage (Fig. 10.6). It can be unilateral or bilateral. A recent study suggested it is more often bilateral in men than in women (Besli et al 2004). It varies in size from 0.2 to 2 mm.
It plays a vasomotor and vasosensory role and participates in the sense of smell. It is also a vestige of our animal life when the sense of smell was essential in the detection of both enemies and sexual partners.
The vomeronasal organ is present in the embryo. For a long time it was thought that the vomeronasal was absent or vistigial and not used in humans. However, recent research has indicated that it does indeed exist in the adult. In 1998, Gaafar et al examined the nasal septum in 200 adults. Instances of the vomeronasal organ varied according to examination technique. With the use of an anterior rhinoscope, the vomeronasal organ was perfectly visible in 32 subjects (16%), whereas with nasal endoscopy, the organ was found in 152 subjects (76%).
The exact function of the vomeronasal organ is not clear, but it does contain pheromone receptors. Pheromones are odorous secretions that play an essential role in sexual attraction and are important for animals in territory recognition. The work of McClintock (1971) has shown that pheromones play a role in the synchronization of the menstrual cycles of cohabiting women (convent, boarding school, prison, and so on).
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