Q.Distinguish between simple squamous, simple cuboidal and simple columnar epithelium on the basis of cell shape, and give one location of each in the body.

Simple epithelium is a single layer of cells resting on a basement membrane, classified by the shape of that one layer. Simple squamous epithelium has flat, plate-like cells with a central flattened nucleus, lining the alveoli of the lungs and capillary walls to permit rapid diffusion of gases. Simple cuboidal epithelium has cube-shaped cells with a central round nucleus, lining kidney tubules and gland ducts for secretion/absorption. Simple columnar epithelium has tall, pillar-shaped cells, often with mucus-secreting goblet cells, lining the stomach and intestine for secretion and nutrient absorption. Ciliated (columnar/cuboidal) epithelium bears motile cilia on the free surface that beat in a coordinated rhythm, lining the trachea, bronchioles and fallopian tubes to sweep mucus, dust or the ovum along the tube. Being only one cell thick makes simple epithelium efficient at diffusion, secretion and absorption, but unsuited to surfaces facing heavy mechanical wear.