Epithelial Cells

Squamous Epithelial

The squamous epithelial cells as you can see are very flat and have cells forming a lump in the centre of it.   They are extremely thin so they can allow material to pass which allows them to have a large surface area that is exposed to the lumen on one side and to the basement membrane on the other. Simple epithelial cells are found in the walls of several places like blood capillaries and lung alveoli where gas exchange occurs. Kidney glomerulus and tubules where filtration and diffusion processes form urine.
Cuboidal Epithelial

The cuboidal epithelial cells have been given this name because the cells are cube shaped. The cells also contain spherical nuclei. The cuboidal epithelial lines the surface of various ducts of various glands and organs because of this the simple cuboidal cells are able to provide a layer of protection from invading bacteria, foreign particles, abrasion   and excessive water loss to the underlying tissue. They are found in glands like thyroid gland and breast tissue, kidney tubules and sweat ducks. The often make secretions in glandular tissues.
Columnar Epithelial

The columnar epithelial cells are much longer; in fact they are much longer than they are wide. Their nuclei is slightly different compared to the squamous and cuboidal epithelial cells, their nuclei is more oval rather the spherical. Through the basement membrane the cells receive nutrients, which separate the cells from the capillary basal layer.Simple columnar epithelial cellsfulfil so many functions because theyare some of the most prolific cells in the body. Their main function is protection. For example it provides impermeable barrier against any bacteriain the stomach and digestive tract. These cells are found throughout the body's organ system like the female reproductive system. They are found is respiratory system and also found on lining the trachea, bronchi and villi in the small intestine.
Ciliated Columnar Epithelium