The lymph is the fluid around the cells (interstitial fluid) that has entered the lymphatic vessels.
Lymph word origin: from Latin lympha = a goddess of fresh water 
The lymph is derived from the interstitial fluid that surrounds the body cells.
When the arterial blood reaches the arterial capillaries, most of it flows into the venous capillaries, but about 10% of the blood plasma (the blood fluid without the cells) escapes the capillaries and forms the interstitial fluid around the cells. When this fluid enters the lymphatic capillaries it becomes the lymph.
Medically, the formation of lymph is called lymphogenesis.
The lymph appears as a translucent, colorless or slightly yellow fluid. It is similar to the blood plasma and is composed of [2,5-s.15]:
- Water (96%)
- Lipids, mainly in the form of chylomicrons, which contain triglycerides and phospholipids
- Proteins derived from the blood and body cells: albumins, globulins, clotting factors, tissue proteins, enzymes, antibodies
- Products of the cell metabolism: urea, creatinine
- Minerals: sodium, chloride, calcium, potassium, bicarbonate
- Lymphocytes, mainly type B, which come either from the arterial blood that supplies the lymph nodes or are created in the lymph nodes themselves
- Occasional foreign particles, microbes and cancerous cells
The composition of the interstitial fluid and lymph is very similar, except that lymph contains more lymphocytes.
The chyle–a thick milky fluid that flows from the small intestine via the intestinal lymphatic trunks to the cisterna chyli and thoracic duct–is a mixture of the lymph and chylomicrons, which are composed of the absorbed dietary triglycerides, cholesterol and proteins .
The lymph flows via the lymphatic vessels through a series of the lymph nodes, which filter out foreign bodies, microbes and cancer cells. The lymph vessels merge into the lymphatic trunks and further into the left and right lymphatic duct, which deliver the lymph to the blood in the subclavian veins at the root of the neck.
The lymph flows only in one direction – from the tissues to the venous blood. In adults, about 120 mL of lymph per hour or 3 liters per day is formed [3,15-s.16].
- Transports the excessive interstitial fluid back to the blood circulation
- Carries foreign bodies, microbes and cancerous cells toward the lymph nodes, where they are destroyed
- The anatomy of the lymphatic vessels, trunks and ducts
- The location and drainage areas of the lymph nodes