Unit I

Pseudostratified epithelium: Single layer of columnar cells all resting on the basement membrane. Theyare of different heights and so the nuclei of the cells appear to be placed one above the other, giving astratified appearance. e.g. lining of the respiratory tract and male genital tract.Pseudo stratified ciliated columnar epithelium: In this epithelium, some of the columnar cells show presenceof cilia eg. Respiratory tract, uterine tube. The pseudostratified ciliated columnar epithelium of the respiratorytract also shows presence of goblet cells and referred as Respiratory epithelium.In this variety, the mucoussecreted by the goblet cells forms a film on the luminal surface and the ciliary beating moves the mucousladen with inspired dust particles. The basal cells, which do not reach the surface, probably serve as stemcells for the taller kind of cells when they are lost from the membrane. The short motile cilia are morenumerous and close together. Cilia arise from basal bodies located just beneath the surface membrane ofthe columnar cells. The basal bodies of adjacent cells give the appearance of continuous membrane e.g.Trachea, Bronchus.Pseudostratified columnar epithelium with stereocilia: In this variety the columnar cells which reach thelumen show very long stereocilia. They are nonmotile or false cilia, which are actually long and branchingmicrovilli. These columnar cells apparently function primarily as absorptive cells. e.g. Duct of epididymis,Dutus deferens.Notes:17