Dilataation

Dilatation is the process of becoming wider or larger, or the act of expanding a passage, cavity, or opening. It is used in several disciplines with related but context-specific meanings. In common medical and anatomical usage, dilation or dilatation refers to the widening of a hollow structure such as a blood vessel, a pupil, the cervix, or other ducts. Dilation can be physiological, such as vasodilation driven by neural or chemical signals, or pathological, as in distension caused by obstruction or dilation of a hollow organ.

In mathematics, dilatation (often called a dilation) is a similarity transformation that enlarges or reduces a figure with respect to a fixed center. A point P maps to P' along the line joining P with the center, with distances scaled by a factor k. If k>1 the figure expands; if 0<k<1 it contracts; k<0 reflects across the center as well. Dilatations preserve the shapes of figures (they are similarity transformations) but not necessarily their absolute size.

In physics and materials science, thermal dilatation describes the expansion of materials with temperature. The linear, area, or volumetric expansion is governed by coefficients of thermal expansion. In engineering contexts, dilatation is used to describe opening of joints, like dilatation joints, that accommodate expansion and contraction to prevent cracking.

Clinical procedures occasionally involve dilatation, such as cervical dilation in labor or esophageal dilatation techniques to treat strictures. Drug- or procedure-induced dilation can be intentional, short-term, or part of diagnostic workups.