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 ?
Specifically, ovarian cancer metastatic to the breast parenchyma can present as a focal mass without definite characteristic radiographic features (6); however, a few studies reveal that serous ovarian carcinoma metastatic to axillary lymph nodes can occasionally demonstrate a peripheral amorphous lymph node calcification pattern on a mammogram (7), which is related to psammoma body formation.
One of the early classification systems was introduced by Michaeli et al; the plain radiograph and intravenous pyelogram were used to categorize EPN into three stages: Stage I describes gas in the renal parenchyma or perinephric tissue; stage II describes gas in the kidney and its surroundings; and stage III indicates extension of gas through fascia or bilateral disease.
The water-conducting tissue, which is called wood or secondary xylem, is a complex tissue containing fibers, parenchyma cells, and tracheary elements (Figure 4).
The California red scale SB moves perpendicularly into the palisade parenchyma and then obliquely or parallel to the spongy parenchyma, keeping more than 85% of its length in both parenchyma tissues.
By this time the apotracheal and paratracheal axial parenchyma gets completely degraded forming holes close to xylem vessel elements (fig 8).
There are two main plant tissues of interest in our analysis here: vascular tissues and parenchyma, which together comprise the basic tissue types analysed and used to make interpretations in this investigation.
According to Figure 3 a, many parenchyma cells in the control group were full of starch granules, but there were hardly any starch granules in parenchyma cells (Fig.
Herein, we presented a case of multilateral coronary fistulas originating from proximal left anterior descending artery (LAD), circumflex artery (CX) and RCA and terminating in the lung parenchyma with multiple tracts.
On the ultrasonographic examination, thyroid gland size was found to be enlarged and parenchyma was heterogeneous with increased blood flow pattern.
However, invasive carcinoma can invade to liver parenchyma, or metastasize.
Maximising growth rate between 2 and 8 weeks of age might have positive effects on mammary development since increased energy and protein intake at this age nearly doubled the mass of mammary parenchyma (Brown et al.
High-grade UC of the upper urinary tract frequently presents as an infiltrative mass that may extensively involve the renal parenchyma, mimicking high-grade RCCs.