Nasal anatomy and physiology

Nasal anatomy and physiology. The nose is the first organ of the respiratory tract. The structure of the nasal cavity is shown in Fig. 2.8. 

NASAL ANATOMY AND PHYSIOLOGY 5.6.2.1 Structure of Nasal and Olfactory Mucosa... 

Recently, a comparison study of deposition pattern of aqueous nasal spray pumps and non-portable nebulizers was published. The obtained controversial results showed a relative standard deviation of 35-80%. This demonstrates the variations in nasal anatomy and physiology from individual to individual. Other stud-ies indicate that differences in the spray performance, i.e., spray angle and particle size distribution, of delivery systems do not necessarily result in different in vivo deposition. 

Following the discussion in the section on Nasal Anatomy and Physiology , it is apparent that data on droplet size and spray angle from a nasal device are important for the regulatory authorities. This section reviews the types of nasal devices available, discusses clinical studies on spray angle and droplet size and reviews device testing. 

Negus V.E. (1958). Comparative Anatomy and Physiology of the Nose and Para-Nasal Sinuses. Oliver Boyd, Edinburgh, p. 402. 

F. M. Baroody. Nasal and paranasal sinus anatomy and physiology. Clin Allergy Immunol 19 1-21 (2007). 

Anatomy and physiology. The human respiratory system is divided into upper and lower respiratory tracts. The upper respiratory system consists of the nose, nasal cavities, nasopharynx, and oropharynx. The lower respiratory tract consists of the larynx, trachea, bronchi, and alveoli, which are composed of respiratory tissues. 

In order to understand the delivery and absorption of drugs by the nasal route and appreciate the factors that may affect it, one must begin with a clear picture of the anatomy and physiology of the nose. 

The entire nasal cavity is lined by pseudostratilied squamous epithelium with a cover of a thin layer of mucus providing immune and mechanical protection. Cilia beat in the mucus about 1000 times per minute and surface material is moved along at a rate of 3-25 mm/min. This transport is unidirectional and moves mucus and any trapped inhaled particles back toward the nasopharynx, where it is periodically swallowed. Drug delivery to the lung is therefore likely to be markedly reduced in the presence of excess mucous seCTetion. Further details of the anatomy and physiology of the nasal cavity can be found in published reviews (24,29,30). 

The upper respiratory tract, particularly the nose, has a unique anatomy that performs normal physiologic functions as well as innate defense against inhaled toxicants. The nose extends from the nostrils to the pharynx. Inspired air enters the nose through the nostrils. The nasal cavity is divided longitudinally by a septum into two nasal compartments. In most mammalian species, each nasal cavity is divided into a dorsal, ventral, and middle (lateral) meatus by two turbinate bones, the nasoturbinate and maxilloturbinate. These turbinates project from the dorsolateral and ventrolateral wall of the cavity, respectively. In the posterior portion of the nose, the ethmoid recess contains the ethmoturbinate. The nasal cavity is lined by a vascular mucosa that consists of four distinct types of epithelia. In rodents, these epithelia are (1) the stratified squamous epithelium that lines the nasal vestibule and the floor of the ventral meatus in the anterior portion of the nose (2) the non-ciliated, pseudostratified, transitional epithelium that lies between the squamous epithelium and the respiratory epithelium and lines the lateral meatus (3) the ciliated respiratory epithelium that lines the remainder of the nasal cavity anterior and ventral to the olfactory epithelium and (4) the olfactory epithelium (neuroepithelium) that lines the dorsal meatus and ethmoturbinates in the caudal portion of the nose. The relative abundance and exact locations of these upper respiratory epithelium differ among mammalian species. 

Mygind, N., and R. Dahl. 1998. Anatomy, physiology and function of the nasal cavities in health and disease. Adv Drug Deliv Rev 29 3. 

Mammalian Olfaction, Reproductive Processes and Behavior" (1976) which was edited by one of the wave of younger researchers, R. L. Doty, deals specifically with mammals, as the title shows. It contains up-to-date information on the role of smell in the reproductive behaviour and endocrinology of mammals, and in addition, accommodates chapters on the anatomy, physiology and development of the nasal chemosensory pathways and an important critique of the pheromone concept in mammalian chemical communication by J. R. Beauchamp, R. L. Doty, D. G. Moulton and R. A. Mugford. A review of reproductive endocrine influences on human nasal chemoreception emphasizes the pressing need for more intensive critical investigation of the behavioural role of olfaction in humans, a line of research which, in fact, Doty subsequently followed up. 

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