Vascular permeability refers to the ability of blood vessel walls to allow substances, such as fluids and proteins, to pass through them. This process is crucial for maintaining proper tissue function and responding to injury or infection. When blood vessels become more permeable, they can facilitate the movement of immune cells and nutrients to areas that need repair or defense. Changes in vascular permeability can occur due to various factors, including inflammation, injury, or certain diseases. Increased permeability can lead to swelling and fluid accumulation in tissues, while decreased permeability may hinder the delivery of essential substances. Understanding this concept is vital for developing treatments for conditions like edema and inflammatory diseases.