(a) What is lymphatic system ? What are its functions?
(b) What is blood pressure ? What are the two factors used to express the blood pressure of a person?
(c) Name the main nitrogenous waste in the human blood. How is it removed from the blood ?

(a) The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, lymph tissues, lymph capillaries, and a network of lymphatic vessels in the human body that are part of the circulatory system and the immune system.

Following are the functions of the lymphatic system:

1. It primarily functions as a defence mechanism in the body by transporting lymph, a fluid containing infection-fighting white blood cells, throughout the body.

2. It also helps in removing excess fluids from body tissues to get rid of toxins, waste, and other unwanted materials from the body.

(b) Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels (arteries and veins) pumped by the heart. 

The two factors used to express the blood pressure of a person are- 

1. Systolic pressure.

2. Diastolic pressure.

(c) Urea is the main nitrogenous waste in human blood. It is removed from the blood by the help of the kidneys in the form of a dilute solution called urine.