# Involution

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## involution

[‚in·və′lü·shən]
(biology)
A turning or rolling in.
(embryology)
Gastrulation by ingrowth of blastomeres around the dorsal lip.
(mathematics)
Any transformation that is its own inverse.
In particular, a correspondence between the points on a line that is its own inverse, given algebraically by x ′ = (ax + b)/(cx-a), where a 2+ bc ≠ 0.
A correspondence between the lines passing through a given point on a plane such that corresponding lines pass through corresponding points of an involution of points on a line.
(medicine)
The retrogressive change to their normal condition that organs undergo after fulfilling their functional purposes, as the uterus after pregnancy.
The period of regression or the processes of decline or decay which occur in the human constitution after middle life.

## Involution

(raising to a power), an algebraic operation consisting in repeating a quantity a n number of times:

The number a is the base of the power, n is the exponent, and an is the power. For example, 3x3x3x3 = 34 = 81. The second power of a number is called its square and the third power, its cube.

## Involution

(regression), in biology, a reduction or loss, in the process of evolution, of certain organs, and a simplification of their organization and functions (for example, various degrees of intestinal reduction in certain parasitic worms and arthropods). Degenerative changes in protozoans and bacteria caused by unfavorable conditions in the habitat are also called involutional. In medicine, the term sometimes refers to atrophy of organs and tissues, such as in aging.

References in periodicals archive ?
Surgical techniques for the treatment of involutional entropion include the lateral tarsal strip procedure [13], the use of transverse everting sutures [1, 14], retractor plication [1,15], transverse lid split [1], and the Wies procedure [14,16].
The cervical and uterine involutional changes and any abnormal discharges observed on days 7, 14, 21, 28, 35 and 42 post-partum are presented in Table 3.
In acupuncture-related lipoatrophy there is an involutional pattern with thin and elongated fat lobules.
In contrast, 1st-and 2nd-grade students present an involutional pattern according to these levels of abstraction, except for verbal problems, where their achievement is the highest, along with the 3rd-grade students.
During the involutional phase, they show evidence of fatty infiltration and decrease in size.
Depression is classically associated with the hormonal and reproductive changes in a woman's life cycle, from premenstrual disorders to the menopause, charmingly labelled as 'involutional melancholia'.
This is not surprising, he said, because the urethra and trigone are just as heavily endowed with estrogen receptors as are the lower vagina and vulva and just as susceptible to involutional change with estrogen deficiency.
Other autopsy findings included marked involutional changes of the thymus and perithymic hemorrhages, focal acute inflammation of the colonic serosa and a bilateral acute bronchopneumonia with extensive pulmonary hemorrhages; this last finding representing the immediate cause of death in this patient with multiorgan failure.
Primary osteoporosis has been subdivided into idiopathic osteoporosis and involutional osteoporosis.
Doctors have a word for this kind of introspective behaviour - it's involutional - and I suppose the ultimate expression of it is retiring to bed and never leaving one's room, which a surprising number of people do at the end of their lives.
In a book filled with pseudo-information and endlessly re-routed mechanisms of communication, the section is unusual for its unambiguous didacticism: Wallace unpacks, though maintaining a characteristic ludic inflection, the meaning of two distinct kinds of depression: "anhedonia or simple melancholy" (692) and 'clinical depression or involutional depression or unipolar dysphoria' (695).

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