The lymphatic system is an addition to the blood circulatory system in the body. It performs many functions similar to blood. It plays a key role in
- Body immune defense.
- Exchange of gases
- Exchange of Nutrients
- Transfer of hormones
- Absorption of fats in the intestine.
The lymphatic system comprises of lymphatic organs, lymphocytes and lymph.
Body immune defense: Lymphatic system is a pathway which is adjacent to the blood circulatory system. Its main function is to drain the substances from tissues back into the blood. While the waste from tissues is drained, any microbes present would be killed by lymphocytes.
Further, it also contains antibodies which are directed against pathogens. Thus, pathogens are prevented from spreading all over the body.
Exchange of gases: The carbon-dioxide from body cells and tissues which is in dissolved form in plasma is drained back to blood and lungs. This carbon dioxide exists as HCO3- and H+. When exchanged back into the air, it gives up CO2 and forms H2O (water). Sometimes, this can also be excreted through kidneys.
Exchange of Nutrients: Lymph is formed when plasma from blood leaks through capillaries of arteries. This leaked fluid has all the nutrients present in the blood. This fluid reaches each cell and tissue and supplies nutrition.
Absorption of fats in the intestine: Fats are not easily digested in the digestive tract. But, they are broken down into fatty acids due to the action of the enzyme lipase. These fatty acids are also not absorbed by diffusions like carbs and amino acids. Hence, specially formed projection called villi is present in the intestine which helps the process. These villi consist of lacteals which open into lymph capillaries. The fatty acids are absorbed by here and the lymph carries them away into the blood.
Transfer of hormones: Lymphatic system also transports hormones in the body. Since hormones are carried by blood, they are also present in lymph. These are distributed by lymph to cells and tissues.
Further, lymphatic system vessels produce hormone endothelin. This is useful for production vasoactive substances like Nitric Oxide.
The lymphatic system helps in body defense though lymph organs like tonsils, appendix and spleen.