To go on living, the body's cells need food, water, chemicals, and :
helium
oxygen
vegetables
carbon dioxide
Main cause of emphysema, a serious disease of respiratory tract is:
Polluted water
Tobacco smoking
Uncooked food
Polluted air
What is the respiratory system?
The body's breathing system
The body's system of nerves
The body's food-processing system
The body's blood-transporting system
Which organ is made up of air-carrying tubes and tiny sacs?
The brain
The lungs
The stomach
The diaphragm
1. Only very few cells are exposed to the environment. 2. They have high oxygen requirements .3. Their respiration is complex than inactive animals.
Which part contracts and flatten out and pull downward during breathing?
Alveoli
Erythrocytes
Trachea
Diaphragm