Q.What is the difference between lymph and blood?

Blood and lymph are related fluids, since lymph is derived from blood, but they differ in what they carry:

• Blood is red and contains a full set of formed elements — red blood cells, white blood cells and platelets — along with plasma rich in proteins.
• Lymph is colourless. It lacks red blood cells and platelets, and among the formed elements it carries mainly lymphocytes. …

To see how lymph and blood differ, it helps to remember where lymph comes from. As blood flows through the tiny capillaries in the tissues, some of its water and small dissolved substances seep out into the spaces between the cells, while the larger proteins and most of the formed elements are too big to leave and stay behind in the vessels. The escaped fluid becomes tissue fluid, and once it is gathered into the lymphatic vessels it is called lymph. This origin explains almost every difference between the two.

Colour. Blood is red because its red cells are loaded with haemoglobin. Lymph, having left those red cells behind, is a colourless fluid.

Formed elements. Blood carries the complete range of formed elements — erythrocytes, leucocytes and platelets. Lymph, by contrast, lacks red blood cells and platelets; the cells it does contain are chiefly lymphocytes, the cells that carry out the body's immune responses. …

Method: Comparing Two Related Body Fluids or Structures

Use this approach for any "difference between" question involving two things that are biologically related.

Steps

Step 1: Establish the relationship or origin connecting the two things

Here, lymph is derived from blood — establishing this first explains most of the differences that follow, rather than treating them as an unrelated list of facts.

Step 2: Choose a small, fixed set of comparison points

Pick points that matter for this pair — colour, cellular content, protein content — so the answer is organised around a structure rather than a jumble of isolated facts.

Step 3: State the value for BOTH things, side by side, for each point …