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Simple columnar epithelium is an epithelial tissue where the cells are up to four times as tall as they are wide. Its major characteristic is that it is uni-layered, meaning it has only a single layer of cells, with the cells being closely packed in long, thin, repeating patterns of columns. This is the primary tissue type lining the surfaces, or mucosa, of the digestive tract organs such as the stomach and the intestines.
Divided into two major categories, simple columnar epithelium is either ciliated or non-ciliated. Ciliated epithelium contains highly concentrated masses of small, thread-like filaments on its surface that vibrate in wave patterns. This vibratory movement extends throughout the length of the digestive tract and helps to move ingested substances along to different digestive organs, such as the stomach and intestines.
Epithelial tissue lines the inner and outer surfaces of the entire human body, and it is differentiated according to the type of surface it lines or covers. It can have several layers with three primary types: squamous, or flattened; cuboidal, shaped like a cube; or columnar, shaped like a column. Simple columnar epithelium is a single layer of columnar epithelial tissue resting upon a membrane or basement membrane that contains fibers for anchoring this tissue to other structures and organs. Moreover, this tissue is termed endothelium when it lines the inner surfaces of body organs, and it is called exothelium when it lines their outer surfaces.
This distinction in terminology is important when identifying disorders or cancers affecting columnar epithelial tissue. Since this epithelial tissue extends throughout the entire range of the digestive system, it is highly exposed to ingested toxins and bacteria, ranging from the mouth and throat region down to the anal canal, where waste material is eliminated. This tissue is also highly subject to carcinomas, or cancers, which may in part be due to its ability to undergo rapid regrowth rates; the cells can produce rapidly growing cancers, as well as natural cell regeneration.
The structural formation of simple columnar epithelium along the basement membrane may help to prevent spreading of a gastric cancer that develops locally within the stomach or intestines, termed a carcinoma in situ. This membrane serves as a wall to stop cancer cells from going down into the deep tissues and helps confine the cancer in its early stages to a more limited region. Such regional cancers have a high risk of growing and spreading, however, and early medical management is of primary importance in this regard.