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 ?
16) Pleural fluid can be seen with or without a pulmonary parenchymal finding.
During the 12-month surveillance period, no patients who had respiratory symptoms but no pulmonary parenchymal involvement were positive for MERS-CoV by PCR, and the positive predictive value of signs and symptoms increased with the severity of clinical manifestation.
On histochemistry, fat stains (oil red O, Sudan black) will usually show that the amount of intracellular fat is significantly less than it is in normal or suppressed parenchymal cells.
Data pertaining to basic demographics, indications for surgery, parenchymal transection techniques, morbidity, mortality and histology results were collated.
The frequency of radiographic parenchymal abnormalities is nearly 5% and is predominantly seen as basal reticular pattern which may become diffuse by time and progress to honeycombing (9).
In this regard, the parenchymal lesions in the spinal cord (MRI) of our patient were consistent with infarction, which supports the diagnosis of ASCS.
Due to lack of visualization of intra parenchymal cysts on CT scan the diagnosis of neurocysticercosis was initially missed.
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Drug-induced pulmonary diseases due to beta-blockers have been published previously as pulmonary parenchymal infiltration and pleurisy, but bilateral multifocal and extensive pleural thickening alone has not been mentioned previously.
There is no FDA-approved treatment for IPF, a progressive, irreversible diffuse parenchymal lung disease of unknown etiology that is typically diagnosed after age 50.
The CE mark allows immediate, unrestricted commercial distribution of BioFoam in the European Community (EC) for use as an adjunct in the sealing of abdominal parenchymal tissues (liver and spleen) when cessation of bleeding by ligature or other conventional methods is ineffective or impractical.
We have demonstrated the cerebral perfusion-enhancing and parenchymal oxygen extraction-increasing effects of vinpocetine in subacute ischaemic stroke patients by near infrared spectroscopy (NIRS) and transcranial Doppler (TCD) methods.