constrictor

Constrictor is a term used in biology to describe something that tightens or narrows a passage or space. In anatomy, constrictors are muscles or structures that reduce the diameter of a lumen or aperture, such as the constrictor pupillae muscle that narrows the pupil or the pharyngeal constrictor muscles that help move a food bolus into the esophagus.

In herpetology, constrictor most often refers to constrictor snakes—boas and pythons—that kill by constriction. These non-venomous snakes seize prey and coil around it, tightening their loops to impede respiration and circulation until the prey suffocates or dies. They can ingest prey much larger than their head size due to flexible jaws and elastic skin. Boas (Boidae) give birth to live young, while pythons (Pythonidae) typically lay eggs, with some maternal involvement in incubation. Constrictor snakes inhabit a range of environments across the Americas, Africa, Asia, and Australia, from tropical forests to grasslands and wetlands. Species vary widely in size, from small constrictors to large ones such as the green anaconda or reticulated python. They are popular in the exotic pet trade but require significant care and appropriate legal permissions in many regions.

Beyond anatomy and reptiles, constrictor can describe any muscle or mechanism that narrows a passage, including sphincters and other circular muscles in various organ systems. The term emphasizes the action of constriction as a means of control or propulsion within biological contexts.