Examples of simple epithelia. A Examples of simple epithelia. A. Section of the kidney containing simple low parietal cells (arrows) that line renal corpuscles. These cells form a barrier that prevents urine from escaping into the surrounding tissue. B. Section of the kidney showing simple cuboidal cells (*) that line some of the tubules in the kidney medulla, which conduct and process urine. Other tubules are lined by columnar cells (arrow). C. Section of the jejunum containing simple columnar epithelial cells that line the surface of this region of the small intestine; the arrow indicates the row of nuclei in the columnar cells. The apical portion of these cells is covered with microvilli. D. Section of the trachea showing the pseudostratified ciliated columnar epithelium that lines this airway. The vertical arrow indicates the height of the epithelium. This epithelium appears to be stratified, instead of simple, because of the staggered array of nuclei. The small arrow indicates a mucus-secreting cell. Many of the cells bear long, thin cilia on their surface. Source: EPITHELIUM, The Big Picture: Histology Citation: Ash R, Morton DA, Scott SA. The Big Picture: Histology; 2017 Available at: https://accessphysiotherapy.mhmedical.com/DownloadImage.aspx?image=/data/books/2058/ashhist_ch1_f004.png&sec=155783779&BookID=2058&ChapterSecID=155783723&imagename= Accessed: November 14, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved