Parenchyma

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Parenchyma

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)

Parenchyma

 

(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.

parenchyma

[pə′reŋ·kə·mə]
(botany)
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.
(histology)
The specialized epithelial portion of an organ, as contrasted with the supporting connective tissue and nutritive framework.
References in periodicals archive ?
There were (57 of 89) were cortical cyst, (22 of 89) were parenchymal cyst, (4 of 89) were medullary cyst, (4 of 89) were parapelvic cyst and (2 of 89) were extraparenchymal cyst.
Brain parenchymal, subarachnoid racemose, and intraventricular cysticercosis in an Indian man.
In the present case, we treated our patient as NBD with parenchymal involvement, while there have been no controlled or comparative trials of treatment of any aspect of neurological involvement in BD.
In the literature, all reported cases with beta-blocker induced pleuropulmonary complications presented with symptoms such as chest pain, cough, and dyspnea since they had pleural effusion and/or parenchymal infiltration (3-7).
Distribution of messenger RNAs of insulin-like growth factor (IGF)-binding proteins-1 and -3 between parenchymal and nonparenchymal cells in rat liver.
In its simplest form a mammoplasty will allow some skin excision that will create a smaller breast form, disguising the underlying parenchymal resection.
The pathological lesions with greater frequency in encephala from mice inoculated with amniotic liquid were parenchymal hyperemia, edema and inflammation manifested in a mild intensity and the other lesions observed were of discrete intensity.
In the present study a significant percentage of these patients showed additional parenchymal abnormalities like alveolar space abnormality including both ground glass attenuation and consolidation.
SAIDs also were associated with parenchymal abnormalities and with restrictive spirometry but not strongly with pleural abnormalities (Table 2).
A range of chronic and disabling conditions, including cognitive impairment, learning disabilities, psychiatric disorders, functional disabilities, sensory impairment, and mobility disorders are associated with the particular neonatal neurologic insults of intraventricular hemorrhage, ventriculomegaly, and periventricular parenchymal damage (Aziz et al.
The publication, "Protection Against TNF-Induced Parenchymal Cell Apoptosis during Endotoxemia by a Novel Caspase Inhibitor in Mice," appeared in the November 15, 2000 issue of Toxicology and Applied Pharmacology (volume 169, pp.