Constricts

Constricts is the third-person singular present tense of the verb constrict. It denotes causing narrowing or tightening by applying pressure, or limiting something in extent, scope, or freedom.

In biology, constriction is a common physiological process. Vasoconstriction narrows blood vessels, reducing blood flow and heat loss in response to cold or stress. Bronchoconstriction narrows airways, which can occur during allergic reactions or inflammatory conditions. Sphincters and other smooth muscles may constrict passages such as the digestive tract, urinary tract, or pupil, regulating flow, tone, and pressure. Constriction is typically controlled by the autonomic nervous system and various signaling molecules.

In physics and engineering, constriction refers to the narrowing of a channel or duct. A constricted cross-section increases flow resistance and can raise pressure upstream while reducing the volume flow rate. The relationship between radius and resistance in laminar flow is exemplified by Poiseuille's law, which shows that small changes in radius have large effects on flow in pipes and vessels.

In medical contexts, constricting agents or mechanisms may be used to stop bleeding or regulate tissue perfusion. Conversely, pathological constriction—such as sustained vasoconstriction—can contribute to disorders like hypertension or ischemia. Understanding constriction helps explain a wide range of physiological responses, mechanical designs, and clinical interventions.

Etymology traces constrict back to Latin constringere, meaning to bind together or confine.