What causes swelling after impact?

Question

Why does the head swell after getting hit by something hard? What is the liquid that forms after impact?

Answer 1

Swelling is caused by increased blood flow to the injured area. Effectively the swelling acts as a cushion to prevent further injury and use of the injured area. White blood cells will also rush to the area to prevent any potential infection.

Answer 2

Swelling due to an impact or trauma, at the cellular level, is largely due to cell damage. The mechanical force of the impact causes damage to the cells or tissues, which causes a cascade of effects. The damaged cells release a plethora of cytokines, which increases blood flow to the damaged area. This increased blood flow causes the reddness and heat associated with swelling. The cytokines also increase vascular permeability, which allows the serum fluid to escape the vascular system and enter the interstitium, or the area where the cells reside. The combined effect of increased blood flow and vascular permeability result in a large volume of fluid to deposit within the interstitium of the damaged area, which we commonly refer to as swelling.

Answer 3

Swelling is any abnormal enlargement of a body part. This can be due to fluid - including blood - bony malformation, muscle, or any number of things. Edema describes fluid, or swelling, that has accumulated in the tissue. Acute swelling refers to swelling that occurs within 24 hours of injury. If the swelling occurs within the first 2 hours, it is probably associated with hemarthrosis (blood in edema), and should be checked out by a physician. Chronic swelling refers to swelling that occurs over a long period of time, and can be difficult for an athlete to detect, but is dangerous if left untreated.