What term is used to describe the functional portions of a gland or solid organ?

The term "parenchyma" refers specifically to the functional tissue of an organ or gland, which is responsible for its specific physiological activities. In the context of solid organs, this includes the living cells that perform the essential functions of that organ. For example, in the lungs, the parenchyma comprises the alveoli and surrounding structures that facilitate gas exchange.

In contrast, stroma refers to the supportive connective tissue surrounding the parenchyma, which provides structure and support but does not engage in the primary functions of the organ. Epithelium is a type of tissue that lines surfaces and cavities throughout the body, playing roles in protection, secretion, and absorption, but it is not synonymous with the functional portions of the gland itself. Connective tissue serves primarily as a framework and support system for various tissues and organs, distinguishing it further from parenchyma in terms of functionality.

Overall, understanding the distinction between parenchyma and other tissue types is crucial for recognizing how organs operate both structurally and functionally.