Swelling in the body can be local and temporary or chronic. It is caused by an increased amount of liquid in the tissues, visible and noticeable by touch. However, the tissues in cells don’t swell, it is the amount of liquid in the extracellular space which is increased. The liquid accumulated increases the pressure in the tissues, weakening the blood circulation and the metabolism. The cells move further apart, the distances between blood vessels and cells increase, and the metabolism in the tissue becomes slower. All swelling slows the metabolism, and therefore reduces the oxygen supply.

Normally the body reacts to acute injury by inflammation. The body immediately starts repairing the damage through additional correcting cells and interstitial fluid, which activates pain receptors by increasing the pressure in the tissues. Chronic tissue injury pain, nociceptive pain, is formed when pain receptors react to a strong stimulus, potentially causing tissue injury. Typical nociceptive pain conditions are inflammative pain, ischemic pain and muscle and bone conditions.

Ischemic pain is pain followed by a lack of blood or oxygen. The decreased amount of oxygen causes lactic acid and carbon dioxide to build up in tissues, which causes the pH to drop, acidifying the tissue. This lower pH level activates the pain receptors. Ischemic pain, for example in the back, shoulders and neck is common. It can be felt as a burning or gnawing pain.

The dysfunctions in the lymphatic system can cause a permanent swelling in the body. Swelling is always a sign of the lymphatic system not functioning efficiently. For instance, swelling in the lower limbs and the pelvis area could be a sign of a larger problem in the lymphatic system, where it is unable to remove the regular amount of liquid filtered from the blood vessels. The result might be severe problems in the tissue metabolism and inflammation.

The suction produced by the heart activates the veins’ circulatory system for the lower limbs. The lymphatic system also requires a the proper pressure, for the system to be active. The necessary suction is produced, when the lymphs pass through the thoracic duct, and back into the blood circulation through the intersection of the inner jugular vein and subclavian artery. By absorbing these lymphs the more efficient blood flow creates the necessary suction for the entire lymphatic system.