Fig. 1
From: The microbiome of the upper respiratory tract in health and disease
The upper respiratory tract (a) and its paranasal sinuses (b). a URT with different, typical microbiome sampling sites (AN anterior naris, MM middle meatus, OR olfactory area and nasopharynx) and nasal lining, starting with 1 non-keratinized skin-like epithelium in the nostrils followed by different epithelial types, 2 squamous epithelium without microvilli, 3 transitional epithelium with ciliated cells, 4 pseudostratified columnar epithelium with ciliated cells, 5 pseudostratified columnar epithelium with many ciliated cells. b Sinuses of the nasal cavity