What is the epithelium?

The epithelium refers to a type of tissue that serves as a protective layer covering the surfaces of internal organs and external surfaces of the body. It plays several critical roles, including absorption, secretion, and sensation. It can be found lining the lungs, intestines, blood vessels, and skin, effectively acting as a barrier and interface between different biological environments.

This tissue is characterized by closely packed cells with minimal extracellular matrix, and it lacks blood vessels, relying on adjacent connective tissues for nourishment. The different forms of epithelial tissue (such as squamous, cuboidal, and columnar) can specialize in different functions based on their locations and roles within the body.

Understanding the diverse functions and locations of epithelial tissue is crucial for appreciating how organs and systems work in both health and disease. This is why this option accurately defines what epithelium is and highlights its significance in the context of anatomy and physiology.