Also found in: Dictionary, Thesaurus, Medical, Wikipedia.


A ground tissue of plants chiefly concerned with the manufacture and storage of food. The primary functions of plants, such as photosynthesis, assimilation, respiration, storage, secretion, and excretion—those associated with living protoplasm—proceed mainly in parenchymal cells. Parenchyma is frequently found as a homogeneous tissue in stems, roots, leaves, and flower parts. Other tissues, such as sclerenchyma, xylem, and phloem, seem to be embedded in a matrix of parenchyma; hence the use of the term ground tissue with regard to parenchyma is derived. The parenchymal cell is one of the most frequently occurring cell types in the plant kingdom. See Plant anatomy, Plant physiology

Typical parenchyma occurs in pith and cortex of roots and stems as a relatively undifferentiated tissue composed of polyhedral cells that may be more or less compactly arranged and show little variation in size or shape. The mesophyll, that is, the tissue located between the upper and lower epidermis of leaves, is a specially differentiated parenchyma called chlorenchyma because its cells contain chlorophyll in distinct chloroplastids.

This chlorenchymatous tissue is the major locus of photosynthetic activity and consequently is one of the more important variants of parenchyma. Specialized secretory parenchymal cells are found lining resin ducts and other secretory structures. See Photosynthesis, Secretory structures (plant)



(1) The fundamental tissue in plants. Parenchyma is composed of cells having a polyhedral shape, with the various diameters differing very little from each other. The cells form homogeneous aggregates in the plant body and fill the spaces between other tissues. They serve as part of the conductive and mechanical tissues. As a result of functional specialization of protoplasts, parenchyma cells may perform assimilative, excretive, and other functions. The presence of intercellular substances, especially in diffuse parenchyma with vacuoles, determines the tissue’s role in gas exchange. Parenchyma cells serving support functions may be elongated, branched, or stellate; their walls are thick and often lignified. Living parenchyma cells are capable of division. Phellogen (cork cambium) or, in unusually thick plants, cambium is formed (for example, in beets and certain lianas).

(2) In animals, parenchyma is the phylogenetic precursor of true tissue. It is divided into primary parenchyma and mixed parenchyma. The former is a bond of homogeneous cells without systematic organization. The cells are not fused in a syncytium or separated by interstitial matter (as in the embryos of certain hydroids in the morular stage). Mixed parenchyma is an aggregate of heterogeneous cells distributed randomly, as in the bodies of Acoela. At times, the term “parenchyma” is used to designate the principal functional tissue of the liver, spleen, lungs, and glands. It is also used to designate striated muscle tissue.


A tissue of higher plants consisting of living cells with thin walls that are agents of photosynthesis and storage; abundant in leaves, roots, and the pulp of fruit, and found also in leaves and stems.
The specialized epithelial portion of an organ, as contrasted with the supporting connective tissue and nutritive framework.
References in periodicals archive ?
The total intra-hepatic cyst volume, hepatic parenchyma volume, and liver volume (cysts plus parenchyma) were also evaluated using CT analysis system.
Parenchyma could not be reached in 30 (10%) patients.
Immunohistochemical (IHC) stain CD-34 showed a strong positivity for the lining epithelium of the large dilated vascular channels as well as smaller blood vessels and capillaries scattered throughout the splenic parenchyma confirming the diagnosis of CH spleen (Fig.
Cortex composed of oval shaped and small parenchyma cells.
Stones in distal part of the duct and within gland parenchyma were removed by gland excision through extra oral submandibular approach using layered dissection.
The epidermis is one-layered, the cortex is parenchymatous and sclerified cells are not common in the cortical parenchyma (Figures 3C and D).
On HRCT examination, we found multiple variable sized smooth walled cystic lesion diffusely scattered in bilateral lung field with involvement of all the lobes with intervening normal lung parenchyma.
The sequence of features that follow are vessel elements, then imperforate tracheary elements, axial parenchyma, rays, and crystals.
Bronchogenic cysts may occasionally arise within the lung parenchyma rather than the more common mediastinal location.
The echotexture of parenchyma and size of prostate varied considerably between dogs with BPH.