Levysepiteeli

Levysepiteeli is a term used in Finnish histology to describe a sheet of flat, plate-like epithelial cells that forms a single, continuous layer. In English-language histology this tissue type is commonly called simple squamous epithelium or pavement epithelium, though the Finnish term can also be used more broadly to refer to flat epithelial sheets in various contexts. The defining feature is cells that are thin and flattened with a broad, polygonal outline and a relatively flattened nucleus, arranged to cover surfaces with minimal thickness.

Levysepiteeli serves functions where diffusion, filtration, or lubrication is advantageous. It lines blood vessels and the heart (endothelium), the body cavities (mesothelium), and the air sacs of the lungs, as well as certain parts of the kidney and serous membranes. In these locations the epithelium reduces friction and provides a thin barrier for exchange processes. The tissue originates from mesoderm-derived lineages for endothelium and mesothelium, and from endoderm in some internal surfaces, reflecting the diverse embryological origins of simple squamous epithelia.

Pathological changes affecting levysepiteeli can occur with inflammation, edema, or neoplasia; endothelium is commonly involved in vascular diseases, while mesothelioma can arise from mesothelial cells. Overall, levysepiteeli describes a functional class of flat epithelial sheets essential for exchange and lubrication in many organ systems.