parenkyma

Parenchyma refers to the functional tissue of an organ, as opposed to its structural connective tissue. In biology, it is the tissue that performs the main function of an organ. For example, the parenchyma of the lungs consists of alveoli, where gas exchange occurs, while the stroma, the supportive connective tissue, comprises the rest of the lung structure. Similarly, in the liver, hepatocytes are considered parenchymal cells, responsible for metabolic functions, whereas the connective tissue framework is the stroma.

The term parenchyma originates from the Greek words "para" (beside) and "enchyma" (infusion), suggesting tissue that is "poured in" or intimately associated with the organ's function. In botany, parenchyma cells are a type of simple permanent tissue found in various plant organs like roots, stems, and leaves. These cells are typically thin-walled, isodiametric, and capable of dividing, playing roles in photosynthesis, storage, and secretion. They form the bulk of many plant tissues, including pith and cortex. The distinction between parenchyma and stroma is important for understanding organ physiology and pathology, as damage or disease often affects the parenchymal cells first, impairing the organ's primary function.