Question

Describe cuboidal, columnar and ciliated epithelium.

Answer 1

The body’s first line of protection from physical, chemical, and biological wear and tear are provided by the epithelial tissues. The cells of an epithelium control permeability and allow only selective transfer of materials across a physical barrier. It acts as a gatekeeper of the body. Any substance which enters the body must cross an epithelium. There are structural features that allow the selective transport of molecules and ions across their cell membranes in some epithelium.

Complete answer:
1. Cuboidal epithelium: The cuboidal epithelium or Simple cuboidal epithelium is a type of epithelium which consists of only a single layer of cuboidal cells. They have large, spherical and a central nucleus. Simple cuboidal epithelia can be found in several organs of people and animals, including the surface of the ovaries, the walls of renal tubules, the lining of nephrons, and sections of the eye and thyroid. The cells perform secretion and absorption on these surfaces. In this type of epithelium, the cell height and width are approximately the same.
2. Columnar epithelium: The cells of columnar epithelium are taller than they are wide (column-shaped). Ciliated columnar epithelium and glandular columnar epithelium are the two classifications of columnar epithelium. A single layer of columnar cells attached to the basement membrane, with oval-shaped nuclei which is located in the basal region is termed as a simple columnar epithelium. Simple columnar epithelium lines most organs of the digestive tract which includes the stomach, small intestine, and large intestine in humans. Uterus is also lined by simple columnar epithelium.
3. Ciliated epithelium: The microscopic extensions of apical cell membrane which are supported by microtubules are termed as cilia. They help to move fluids as well as trapped particles. Ventricles of the brain where it helps circulate the cerebrospinal fluid are lined by ciliated epithelium. The ciliated epithelium of the airway forms a mucociliary escalator which helps to sweep particles of dust and pathogens trapped in the secreted mucus toward the throat. Ciliated epithelium is also called as an escalator because it continuously pushes the mucous with trapped particles in it upwards.

Note:
Different epithelial cells have the ability to secrete and release mucus and particular chemical substances onto their apical surfaces. For example, the epithelium of the small intestine releases digestive enzymes, which helps for digestion. Cells that line the respiratory tract secrete mucous which helps in trapping incoming microorganisms and particles. Many secretory cells can be found in a glandular epithelium.