Biology · Body Fluids and Circulation · NEET
They are almost the same fluid at different locations. When water and small substances leak out of blood capillaries into the spaces between tissue cells, that fluid is called interstitial fluid or tissue fluid. When the lymphatic vessels collect this same fluid and start draining it, it is called lymph. So tissue fluid is the source, and lymph is the name once it enters lymphatic vessels. NCERT itself titles the section 'Lymph (Tissue Fluid)', treating them together.
Lymph forms by filtration through the thin capillary wall. Only water and small water-soluble substances pass out easily. The large proteins and the formed elements (RBCs and platelets) stay inside the blood vessels because they are too big to leak out. That is why lymph has no RBCs and no platelets, and only lymphocytes (which can move through vessel walls).
Plasma is the fluid part of blood inside the vessels and is rich in proteins like albumin, globulin and fibrinogen. Lymph is derived from plasma but has much less protein because most proteins stay behind in the blood. Lymph does have the same mineral (ion) distribution as plasma. Lymph also contains only lymphocytes, whereas plasma is the matrix for all formed elements.
Blood looks red because RBCs carry the red pigment haemoglobin. Lymph has no RBCs, so it has no haemoglobin and appears colourless (or pale). This one fact links the colour of a body fluid directly to whether it contains RBCs, a favourite NEET link.
Yes. Fats absorbed from the intestine enter the lymph through special lymphatic capillaries called lacteals present in the intestinal villi. So fat transport is a special function of lymph, not of blood at the point of absorption. Lymph also carries nutrients and hormones.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Lymph is the colourless tissue fluid collected by lymphatic vessels; it is like plasma but with much less protein, no RBCs or platelets, and only lymphocytes.
Lymph drains excess tissue fluid back to the major veins, allows exchange of nutrients and gases between blood and cells, carries out immune responses through lymphocytes, and absorbs fats through lacteals in the intestinal villi.
Lacteals are lymphatic capillaries inside the intestinal villi. They absorb digested fats and carry them in the lymph, which is why lymph after a fatty meal looks milky.
An elaborate network of lymphatic vessels collects the tissue fluid and drains it back into the major veins, returning it to the blood circulation.
Lymph contains specialised lymphocytes, which are responsible for the immune responses of the body. It does not contain RBCs or platelets.
