Parenchyma

Parenchyma is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.

This article is about Parenchyma in animals including humans. For information specific to Plants, see Ground tissue § Parenchyma.
Lung parenchyma showing damage due to large subpleural bullae.

Etymology

The term parenchyma is New Latin from the Greek word παρέγχυμα parenchyma 'visceral flesh' from παρεγχεῖν parenkhein 'to pour in' from παρα- para- 'beside' + ἐν en- 'in' + χεῖν khein 'to pour'.[1]

Originally, Erasistratus and other anatomists used it to refer to certain human tissues.[2] Later, it was also applied to plant tissues by Nehemiah Grew.[3]

Structure

The parenchyma is the functional parts of an organ, or of a structure such as a tumour in the body. This is in contrast to the stroma, which refers to the structural tissue of organs or of structures, namely, the connective tissues.

Brain

The brain parenchyma refers to the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells.[4] Damage or trauma to the brain parenchyma often results in a loss of cognitive ability or even death. Bleeding into the parenchyma is known as intraparenchymal hemorrhage.

Lungs

Lung parenchyma is the substance of the lung outside of the circulatory system that is involved with gas exchange and includes the pulmonary alveoli and respiratory bronchioles,[5] though some authors include only the alveoli.[6]

Liver

The liver parenchyma is the functional tissue of the organ made up of around 80% of the liver volume as hepatocytes. The other main type of liver cells are non-parenchymal. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. [7]

Kidneys

The renal parenchyma (of the kidney) is divided into two major structures: the outer renal cortex and the inner renal medulla. Grossly, these structures take the shape of 7 to 18[8] cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid.[9]

Tumors

The tumor parenchyma, of a solid tumour, is one of the two distinct compartments in a solid tumour. The parenchyma is made up of neoplastic cells. The other compartment is the stroma induced by the neoplastic cells, needed for nutritional support and waste removal. In many types of tumour, clusters of parenchymal cells are separated by a basal lamina that can sometimes be incomplete.[10]

Flatworms

Parenchyma is the tissue made up of cells and intercellular spaces that fills the interior of the body of a flatworm, which is an acoelomate. This is a spongy tissue also known as a mesenchymal tissue, in which several types of cells are lodged in their extracellular matrices. The parenchymal cells include myocytes, and many types of specialised cells. The cells are often attached to each other and also to their nearby epithelial cells mainly by gap junctions and hemidesmosomes. There is much variation in the types of cell in the parenchyma according to the species and anatomical regions. Its possible functions may include skeletal support, nutrient storage, movement, and many others.[11]

References
  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. Virchow, R.L.K. (1863). Cellular pathology as based upon physiological and pathological histology [...] by Rudolf Virchow. Translated from the 2nd ed. of the original by Frank Chance. With notes and numerous emendations, principally from MS. notes of the author. 1–562. [Cf. p. 339.] link.
  3. Gager, C. S. 1915. The ballot for names for the exterior of the laboratory building, Brooklyn Botanic Garden. Rec. Brooklyn Bot. Gard. IV, pp. 105–123. link.
  4. "What is the Brain Parenchyma? (With pictures)".
  5. "Lung parenchyma". Retrieved 9 February 2016.
  6. Suki, B (July 2011). "Lung parenchymal mechanics". Comprehensive Physiology. 1 (3): 1317–1351. doi:10.1002/cphy.c100033. ISBN 9780470650714. PMC 3929318. PMID 23733644.
  7. Kmieć Z (2001). Cooperation of liver cells in health and disease. Adv Anat Embryol Cell Biol. Advances in Anatomy Embryology and Cell Biology. 161. pp. iii–xiii, 1–151. doi:10.1007/978-3-642-56553-3_1. ISBN 978-3-540-41887-0. PMID 11729749.
  8. Ashton, Leah; Gullekson, Russ; Hurley, Mary; Olivieri, Marion (April 1, 2017). "Correlation of Kidney Size to Number of Renal Pyramids in the Goat Kidney". The FASEB Journal. 31 (1_supplement): 899.5. doi:10.1096/fasebj.31.1_supplement.899.5 (inactive 2021-01-11) – via fasebj.org (Atypon).CS1 maint: DOI inactive as of January 2021 (link)
  9. Walter F. Boron (2004). Medical Physiology: A Cellular And Molecular Approach. Elsevier/Saunders. ISBN 978-1-4160-2328-9.
  10. Connolly, James L.; Schnitt, Stuart J.; Wang, Helen H.; Longtine, Janina A.; Dvorak, Ann; Dvorak, Harold F. (2003). "Tumor Structure and Tumor Stroma Generation". Holland-Frei Cancer Medicine. 6th edition.
  11. Conn, D (1993). "The Biology of Flatworms (Platyhelminthes): Parenchyma Cells and Extracellular Matrices". Transactions of the American Microscopical Society. 112 (4): 241–261. doi:10.2307/3226561. JSTOR 3226561.
  • The dictionary definition of parenchyma at Wiktionary
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