Parenkymia

Parenkymia, commonly referred to as parenchyma, is a term used in biology to denote the functional tissue of an organ or organ system, distinct from the stroma, which provides structural support and framework.

In plants, parenchyma is the most abundant type of simple tissue. It is composed of living cells with thin primary walls. These cells are typically isodiametric or variable in shape and may contain chloroplasts, enabling photosynthesis (chlorenchyma), or be specialized for storage of starch and other substances (storage parenchyma), or for forming internal air spaces (aerenchyma). Parenchyma plays roles in photosynthesis, storage, wound repair, and tissue regeneration, and it can be found throughout leaves, stems, roots, and fruits.

In animals and humans, parenchyma refers to the functional tissue of an organ—the cells and tissues that carry out the organ’s specific activities. This is in contrast to the stroma, which includes connective tissue, blood vessels, and supportive scaffolding. Examples include liver parenchyma, composed of hepatocytes performing metabolic and secretory functions; lung parenchyma, consisting of alveolar epithelium and surrounding tissue; and brain parenchyma, formed by neurons and glial cells. Diseases may be described as parenchymal when they primarily affect the functional tissue of an organ.

Terminology: Parenkymia is a less common variant found in some languages or older texts; in contemporary English-language usage, parenchyma is the standard term for the functional tissue of an organ.