Transmucosal Nasal Drug Delivery: Systemic Bioavailability of ...

2. Impact of anatomy and physiology on transmucosal nasal drug delivery
2 Impact of anatomy and physiology on transmucosal
nasal drug delivery
2.1 Anatomy and physiology of the nose
The surface of the nasal cavity is enlarged by three nasal conchae (superior, middle, and inferior),
facilitating purification, humidification and temperature regulation of inspired air [Mygind and Dahl
1998] (see Figure 2-1). The total surface of both nasal cavities is about 150 cm 2 (150-200 cm 2 )
[Merkus 2004] of which the respiratory epithelium covers about 130 cm 2 (large inferior turbinate)
and the olfactory region about 2 cm 2 to 10 cm 2 (superior conchae).
The narrowest portion of the entire upper airway, the internal naris (nasal valve), is located about
1.5 cm from the external naris. The nasal valve accounts for approximately 50% of the total
resistance to respiratory airflow from the nostril to the alveoli.
Figure 2-1: Section of the human nasal cavity, from SEER’s webbased
Training Module [SEER, 2007]
Breathing and olfaction are the prime functions of the nasal cavity. Beside these functions, the
nasal cavity and the paranasal sinuses are important for the resonance of the voice.
The high vascularization of the submucosa facilitates warming up of the inspired air. The
submucosal vascular plexus consists of arterioles, capillaries, semi-permeable post capillary
sinusoids and venules. The post capillary sinusoids regulate resistance and secretory activity of the
nasal mucosa. Vasodilatation and extravasation of plasma resulting in nasal congestion and
rhinorrhoea, is induced by histamine, kinins, substance P, platelet-activating factor, and various
leukotrienes [Foley and Hamid 2006].
Katja Suter-Zimmermann Page 17 of 188 University of Basel, 2008