Lymphatic System in Human

Lymphatic system in human comprises lymph (it is also known as tissue fluid or interstitial fluid). Along with the lymph, there are lymph space/sinus/ lymphatic vessels/ducts, lymph nodes /glands, lymphatic heart, etc.

Lymph = Blood - (RBCs + platelets + fibrinogen+ large protein molecules).

Lymphatic System Formation in Human

Lymph formation occurs from Blood through capillaries. When blood passes to the cells or tissue then small substances along with water passes out through the pores of the wall of capillaries and collect in space forming lymph.

Composition of Lymph in Human

The composition of lymph is the same as plasma but most of the formed elements of blood (RBCs, WBCs, Platelets) and larger protein molecules are absent.

What does Lymphatic System Do?

  • Lymph helps in the exchange of gases.
  • Nutrients supply to the cells from the blood.
  • Lymph also helps in the transportation of nutrients and hormones.
  • It is a colorless fluid and also helps in the absorption of fats in lacteal and through intestinal villi.
  • Lymph has specialized lymphocytes which increase the immune response of the body.
Lymph collects in Lymph Sinus or Lymph Space of the Lymphatic System in Human. The largest lymph sinus is present in amphibians between skin and muscles.

Lymph formation occurs at all the places in the body like-
  • Choroid Plexus of the brain - Cerebrospinal Fluid (CSF).
  • Pericardial fluid - Heart.
  • Pleural fluid - Lungs
  • Perilymph and Endolymph - Ear
  • Aqueous and Vitreous humor - Eye
  • Coelomic fluid - Body Cavity

Collection of lymph

Lymphatic vessels collect the lymph which drains it into the major veins - Subclavian right and left lymphatic vessels. These are collecting vessels like veins and the flow of lymph is undirectional.

The whole body lymph first collects in Cisterna Chyle (present near the heart) and is then brought to Subclavian vein by thoracic duct. Cisterna Chyle is slightly contractile and is therefore known as 2nd Heart of the body.

Lymphatic System Organs in Human

The Lymphatic System in humans comprises of the following organs.

Lymph nodes/Lymph glands

These are bulb or button-like swelling around the lymphatic vessels and there takes the production of WBCs. WBCs fight with Infection. Similar to WBCs are tonsils that fight infections.


It is the largest solid mass of reticuloendothelial system or largest lymphoid organ. Connective tissue covers the spleen known as a capsule and is present in the abdominal cavity on the left side. Internally spleen divides into the red and white pulp. A splenic cord is a continuous partition and finally merges with white pulp.

Functions of Spleen

  • Largest Lymphoid organ
  • Hemopoietic organ
  • Blood bank
  • Graveyard of RBCs
  • Blood filter
  • Shock organ for allergy
In conditions in which RBCs are broken down, the size of spleen enlarges called splenomegaly like in Malaria.

Additional Information

  • Right and Left thoracic duct is the largest lymphatic duct.
  • Cisterna Chyle is known as The Second Heart of the body.
  • Blood has more neutrophils and Lymph has more specialized lymphocytes.
  • There is a barrier mechanism in the Wall of blood capillaries and it develops maximum in the brain called the Blood-Brain Barrier (BBB).
  • Brain, Cartilage, Cornea, hairs do not have an internal blood supply.
  • In the frog circulation of lymph is by 2 pairs of lymphatic hearts but in mammals, circulation is by contraction of muscles and high blood pressure of circulation.
  • Lymph has more of CO2 and Blood has more O2 per unit volume of blood.
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