Parenchyma () is the bulk of functional substance in an animal organ such as the brain or , or a structure such as a tumour. In zoology, it is the tissue that fills the interior of . In botany, it is some layers in the cross-section of the leaf.
Etymology
The term
parenchyma is
Neo-Latin from the
Ancient Greek word παρέγχυμα parenchyma meaning 'visceral flesh', and from παρεγχεῖν parenkhein meaning 'to pour in' from παρα- para- 'beside' + ἐν en- 'in' + χεῖν khein 'to pour'.
Originally, Erasistratus and other anatomists used it for certain human tissues.[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. link .] Later, it was also applied to plant tissues by Nehemiah Grew.[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 .]
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,
and
glial cells.
It is also known to contain collagen proteins.
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.
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Lungs
Lung parenchyma is the substance of the
lung that is involved with
gas exchange and includes the pulmonary alveoli.
Liver
The liver parenchyma is the functional tissue of the organ made up of around 80% of the
liver volume as
. 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.
Kidneys
The
Kidney parenchyma 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
cone-shaped
, each containing renal cortex surrounding a portion of medulla called a
renal pyramid.
Tumors
The tumor parenchyma, of a solid
Neoplasm, is one of the two distinct compartments in a solid tumour. The parenchyma is made up of
neoplasm. 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.
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
mesenchyme, in which several types of cells are lodged in their extracellular matrices. The parenchymal cells include
, and many types of specialised cells. The cells are often attached to each other and also to their nearby epithelial cells mainly by
and
. 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.
External links
