lining cells of the alveoli include all of the following Except:

D i.e. Langerhans cells Langerhans cells are immature dendritic cells, present through out the epidermis but are most clearly identifiable in stratum spinosum. They possess characteristic Birbeck granules and undergo maturation from antingen capturing to antigen presenting cells, and express MHC class I & II molecules. They are found in lymph nodes and activate T lymhocytes. Langerhans cells reach lung during pathological conditions like HistiocytosisQAlveoli mainly contain two types of alveolar epithelial cells (pneumocytes), interalveolar pores of kohn, & alveolar macrophages (dust cells)QType I pneumocytes form >90% of alveolar area, and share a fused basal lamina with adjacent capillary endothelium to form interalveolar septum and blood -air barrier. These are epithelial squamous cells with tight junction. If damaged, non dividing type I cells are replaced by proliferation & differentiation of type 11 cells. Smaller rounded type II cells are often more numerous but contribute only They contin characteristic secretory lamellar bodies form surfactant and line interalveolar pores of KohnQ. Surfactant is produced and recycled by type II pneumocytes and cleared (phagocytized) by macrophages.- In pathological conditions neutrophils - leukocytes & lymphocytes may enter alveoli and respiratory tree and impa sputum a yellow appearance.Conducting airway of trachea, bronchi & broncheoles contain 6 types epithelial cells namely - ciliated columnar cells, goblet cells, basal cells, brush cells, clara cells & neuroendocrinal cells of kulchitsky / APUD cellsQ. Small lymphocytes (mainly T cells) and mast cells migrate into epithelium from underlying connective tissue. Larger conducting airay is lined by pseudostratified columnar predominantly ciliated epithelium. In terminal & respiratory bronchioles there are fewer cilia and cells are low columnar or cuboidal.Goblet cells are present from trachea to smaller bronchi but are normally absent in bronchioles (but found in smokers)- Clara cells are functionally similar to type II pneumocyte & it produce surfactant lipoprotein.Basal cells are mitotic stem cells for other epithelial cells, & are present in larger airways lined by pseudostratified respiratory epithelium.Brush cells are present throughout conducting airway including the respiratory epithelium of nasopharynx. It is in contact with afferent nerve fiber basally & thus have sensory receptor functionNeuro endocranial cells of Kulchitsky or dense core or small granule cells are APUD cells most numerous in fetal lung and decrease dramatically after bih.Regional distribution of cell types Upto terminal bronchiole- Ciliated columnar epithelial cells- Goblet cells- Basal cells- Seromucous gland cells - Neuroendocrine cells- Brush cellsLobular-bronchiole- Ciliated cuboidal epithelium Basal cells- Seromucous gland cells (in upper pa) Brush cellsTerminal bronchiole - Ciliated & nonciliated cuboidalepithelium - Clara cells - Brush cellsRespiratory bronchiole- Ciliated & non ciliated cuboidal epithelium - Clara cells- Type I pneumocytesAlveoli- Type I & II pneumocytes