Parenchyma

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Parenchyma is the bulk of a substance. In animals, a parenchyma comprises the functional parts of an organ and in plants parenchyma is the ground tissue of nonwoody structures.

The term parenchyma is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour".[1]

In plants[edit]

Parenchyma (pale grey) in a plant stem, with scattered veins (darker red)

In plants, "parenchyma" is one of the three main types of ground tissue, and the most common. It can be distinguished through their thin cell wall as compared to other cells. Parenchyma cells make up the bulk of the soft parts of plants, including the insides of leaves, flowers and fruits (but not the epidermis or veins of these structures).[2]

In animals[edit]

The parenchyma are the functional parts of an organ in the body. This is in contrast to the stroma, which refers to the structural tissue of organs, namely, the connective tissues.

In cancer, the parenchyma refers to "The portion of a tissue that lies outside the circulatory system and is often responsible for carrying out the specialized functions of the tissue".[3]

Early in development the mammalian embryo has three distinct layers: ectoderm (external layer), endoderm (internal layer) and in between those two layers the middle layer or mesoderm. The parenchyma of most organs is of ectodermal (brain, skin) or endodermal origin (lungs, gastrointestinal tract, liver, pancreas). The parenchyma of a few organs (spleen, kidneys, heart) is of mesodermal origin. The stroma of all organs is of mesodermal origin.[citation needed]

Examples include:

Organ Parenchyma
brain neurons and glial cells
heart myocyte
kidney nephron
liver hepatocyte
lungs Lung parenchyma in its strictest sense refers solely to alveolar tissue with respiratory bronchioles, alveolar ducts and terminal bronchioles. However, the term is often used loosely to refer to any form of lung tissue, also including bronchioles, bronchi, blood vessels and lung interstitium.[4]
ovary Follicles with egg cells
pancreas Islets of Langerhans and Pancreatic acini
spleen white pulp and red pulp
placenta placental villi, including the fetal vessels, and the maternal intervillous space; non-parenchyma comprises chorionic and decidual plates, fetal vessels of diameter >0.1 cm and intercotyledonary septa[5]

References[edit]

  1. ^ LeMone, Priscilla; Burke, Karen; Dwyer, Trudy; Levett-Jones, Tracy; Moxham, Lorna; Reid-Searl, Kerry; Berry, Kamaree; Carville, Keryln; Hales, Majella; Knox, Nicole; Luxford, Yoni; Raymond, Debra (2013). "Parenchyma". Medical-Surgical Nursing. Pearson Australia. p. G–18. ISBN 978-1-4860-1440-8. 
  2. ^ "Parenchyma". Retrieved 30 December 2014. 
  3. ^ Weinberg (c. 2014). The Biology of Cancer. [page needed]
  4. ^ "Parenchyma Of Lung". Medical Dictionary. [page needed] in turn citing Stedman's Medical Dictionary. 2006. [full citation needed]
  5. ^ Aherne, W.; Dunnill, M. S. (1966). "Quantitative aspects of placental structure". The Journal of Pathology and Bacteriology 91 (1): 123–39. doi:10.1002/path.1700910117. PMID 5941387.