Epithelium consists of a diverse group of cell types, each of which possesses specific functional characteristics. The cells that make up a given epithelium are arranged in close apposition with one another and typically are located at what may be described as the free surfaces of the body. Such free surfaces include the exterior of the body, the outer surface of many internal organs, and the lining of body cavities, tubes, and ducts. Epithelium is classified on the basis of the arrangement of the cells that it contains and their shape. If the cells are present in a single layer, they constitute a simple epithelium. If they are present in multiple layers, they constitute a stratified epithelium. The shape of the cells is typically described as squamous, if the cell is wider than it is tall; cuboidal, if its height and width are approximately the same; or columnar, where the cell is taller than it is wide.
Simple squamous epithelium, mesovarium, human, body. The mesothelial cells (MC) are recognized by their nuclei at this low
H&E, x350; inset x875. magnification. Beneath the mesothelial cells is a thin layer of connective tissue (CT) and adipose cells (A). The inset reveals at higher magnification the
This micrograph shows the surface epithelium of the mesovarnuclei (N) of the mesothelial cells.
ium covered by mesothelium, a name given to the simple squamous epithelium that lines the internal cavities of the
Simple squamous epithelium, mesentery, rat, silver impregnation, x350; inset x700.
This is an intermediate magnification of a whole mount of a piece of mesentery. The mesentery was placed on the slide and prepared for microscopic examination. The microscope was focused at the surface of the mesentery. By this method, the boundaries of the surface mesothelial cells are delineated as black lines by the precipitated silver. Note that the cells are in close apposition to one another and that they have a polygonal shape. The inset reveals several mesothelial cells, each of which exhibits a nucleus (N) that has a round, or oval profile. Because of the squamous shape of the mesothelial cells, the nuclei are not spherical, but rather are disc-like.
Simple squamous epithelium, kidney, human, H&E, x350.
This micrograph shows a kidney renal corpuscle. The wall of the renal corpuscle, known as the parietal layer of Bowman’s capsule, is a spherical structure that consists of a simple squaous epithelium (SSE). The interior of the corpuscle
Simple cuboidal epithelium, pancreas, human, H&E, x700.
This photomicrograph shows two pancreatic ducts (PD) that are lined by a simple cuboidal epithelium. The duct cell nuclei (N) tend to be spherical, a feature consistent with the
Simple cuboidal epithelium, lung, human, H&E, x175; inset x525.
This photomicrograph shows the epithelium of the smallest conducting bronchioles of the lung. The simple cuboidal epithelium consists of cuboidal cells (CC). The inset shows a higher contains a capillary network from which fluid is filtered to enter the  urinary space (US) and then into the proximal convoluted tubule (PCT). Nuclei (N) of the squamous cells of the parietal layer of Bowman’s capsule are ovoid and appear to protrude slightly into the urinary space. The free surface of this simple squamous epithelium faces the urinary space, whereas the basal surface of the epithelial cells rests on a layer of connective tissue (CT).
cuboidal shape of the cell. The free surface of the epithelial cells face the lumen of the duct and the basal surface rests on connective tissue (CT). Careful examination of the free surface of the epithelial cells reveals some of the terminal bars (TB) between adjacent cells.