What are the two main phases of acute inflammation?

The two main phases of acute inflammation are the vascular phase and the cellular phase.

In the vascular phase, there are changes in blood flow and the permeability of blood vessels. This phase is characterized by vasodilation, which increases blood flow to the affected area, leading to redness and warmth. Additionally, the increased permeability allows for proteins and fluid to exit the bloodstream and enter the tissues, contributing to swelling.

The cellular phase follows the vascular changes and involves the migration of leukocytes (white blood cells) to the site of injury or infection. During this phase, leukocytes such as neutrophils and macrophages play critical roles in detecting pathogens, phagocytizing them, and releasing inflammatory mediators. This phase is vital for containing and resolving the inflammatory process.

The concept of these two distinct phases is essential for understanding the progression of an inflammatory response and the body's mechanism for fighting infection and healing tissue damage.