Thelium refers to a specific type of epithelial tissue that lines various bodily organs, cavities, and structures in multicellular organisms. Derived from the Greek word "thēlē," meaning "nipple" or "teat," the term thelium reflects its early discovery in the breast tissue.
Thelium is characterized by its thin, single-layered structure comprising closely packed cells. These cells possess tightly bound cell junctions that form a barrier between different bodily compartments, ensuring selective permeability and protecting underlying tissues. Thelium can be found in organs such as the intestines, lungs, blood vessels, and glands, including mammary glands.
The main functions of thelium include providing a protective barrier, enabling transport and absorption of substances, as well as secreting mucus or other specialized fluids. For example, in the intestines, thelial cells form microvilli that increase the surface area for nutrient absorption. In blood vessels, endothelium helps regulate blood flow, exchange nutrients and waste products, and participate in immune responses.
While thelium predominantly comprises simple squamous or cuboidal cells, it can also be stratified, transitioning to stratified squamous thelium in areas with higher mechanical stress. This type is found in structures exposed to external environments like the skin or oral cavity.
Understanding the structure and function of thelium is crucial in various medical fields, as abnormalities in thelium can lead to diseases such as cancer, ulcerative colitis, or atherosclerosis. Thus, studying thelium is vital in defining and addressing various physiological and pathological mechanisms within the body.
