Characteristics and Origin of the Human Olfactory Organ

Abstract

The structure of human ethmoid bone may be characterized not only by the labyrinthine complexity, but also by asymmetry, numerous variations and deformity. Another important specificity is the co-existence of evoluted and nonevoluted structures. These characteristics are probably the result of encephalization and insufficient adaptation due to rapid evolution since man descended to the ground from his arborial life. Kyphosis of the cranial base, displacement of the lamina lateralis anterosuperiorly and rotating of both orbits antero-medialy, restricted the space where the numerous ethmotubinates were to grow. In quadrupeds and in lower primates, the lamina lateralis serves as the site of attachment for turbinates, exists in the antero-inferior part of the nasal cavity forming a medial wall of the sinus maxillaris. However, in human and in higher class primates also this lamina enters the orbit as the lamina orbitalis or lamina papyracea participating in the medial wall of the orbita. The lamina cribrosa, the other site of attachment of turbinates, displaces to antero-superior upon the nasal cavity. Thus, the course of the basal lamellae of turbinates are forced to bend from an antero-superior to a postero-inferior direction. Then, in human, who have more turbinates (Denker u. Kahler, 1925; Miller, 1964; Negus, 1958) than simiae (Ehara, 1974; Ishii, 1955), numerous basal lamellae with scrolls, compress each other with overlapping, fusion, displacement or deformities. With further compression by a deviated septum and the space-filling effect in its concave side, the ethmoid becomes increasingly complex. The complexity of the human ethmoid bone warrants further anthropological and biostatical study with regard to the pneumatisation theory.