Question

A liquid X of colour Y circulates in the human body only in one direction : from body tissues to the heart. Among other things, liquid X contains germs from cells and dead cells. The liquid X is cleaned of germs and dead cells by a special type of white blood cells called Z. This cleaned liquid is then put into the blood circulatory system in subclavian veins.

1. What is (i) liquid X, and (ii) colour Y?
2. What is Z?
3. The liquid X is somewhat similar to a component of blood. Name this component.
4. Why is liquid X not red?

Answer 1

1. Lymph (X) is a light yellow colour (Y) liquid that circulates in the human body. It circulates from the body tissues to the heart. Hence, (i) the liquid X is lymph. (ii) The colour Y is light yellow.
2. The liquid X (lymph) is cleaned of germs and dead cells by a special type of white blood cells called lymphocytes (Z). Lymphocytes help in fighting infections and diseases. Thus, Z represents lymphocytes.
3. The liquid X, i.e. lymph, is somewhat similar to plasma.
4. The liquid X, i.e. lymph, is not red because it does not contain red blood cells that have a red colour pigment called haemoglobin.