parenchymy

Parenchyma, sometimes spelled parenchymy, refers to the functional tissue of an organ as distinct from the surrounding supportive stroma or connective tissue. The term is used in both plant anatomy and animal histology to describe the cells that carry out an organ’s specific activities.

In plants, parenchyma is a primary component of the ground tissue system. Parenchymal cells are typically living with thin, flexible primary cell walls and large vacuoles. They are relatively unspecialized but capable of division and differentiation, enabling growth and repair. Parenchyma forms most soft tissues such as the mesophyll of leaves, the pith and cortex of stems and roots, and the flesh of fruits. It is versatile in function: chlorenchyma conducts photosynthesis, storage parenchyma stores starch, oils, and other nutrients; aerenchyma contains air spaces that aid buoyancy and gas exchange; and other parenchymal cells may secrete or metabolize substances.

In animals and in medical usage, parenchyma refers to the functional tissue of an organ, as opposed to its stroma (connective tissue, blood vessels, and ducts). The specific cells that constitute an organ’s parenchyma vary by organ—for example, hepatocytes form the hepatic parenchyma of the liver, and neurons and glial cells contribute to the parenchyma of the brain. The term is often used in pathology to describe damage or disease that affects the functional tissue, rather than the supportive framework.