Respiratory System Questions & MCQ — Free Practice with Answers

What is breathing and respiration

Breathing is the physical process of moving air into and out of the lungs. Respiration is the process by which cells in the body use oxygen to break down food (such as digested glucose) to release energy. Breathing brings oxygen into the body for respiration, and removes carbon dioxide produced during respiration.

Parts of the respiratory system

The main parts of the respiratory system are:

• Nose: Air enters the body through the nose. The nose warms, moistens, and filters the air by trapping dust and germs with tiny hairs and mucus.
• Windpipe (trachea): A tube that carries air from the nose down to the lungs. It is kept open by rings of cartilage.
• Lungs: Two spongy organs in the chest where gas exchange takes place. The lungs contain millions of tiny air sacs that provide a large surface area for oxygen and carbon dioxide to move in and out of the blood.
• Diaphragm: A large, dome-shaped muscle below the lungs. It moves down during inhalation and moves up during exhalation to help move air in and out.
• Ribs: The rib cage surrounds and protects the lungs. The rib muscles move the ribs up and out during inhalation, and down and in during exhalation.

How breathing works

Breathing involves two phases:

• Inhalation (breathing in): The diaphragm moves down and the ribs move up and outwards. This increases the space inside the chest, causing the lungs to expand and air to rush in.
• Exhalation (breathing out): The diaphragm moves up and the ribs move down and inwards. This decreases the space inside the chest, causing the lungs to be compressed and air to be pushed out.

Gas exchange

In the lungs, oxygen from the inhaled air passes into the blood, while carbon dioxide from the blood passes into the lungs to be exhaled. This exchange happens in the tiny air sacs of the lungs. The oxygen-rich blood is then carried by the circulatory system to all parts of the body, where cells use the oxygen for respiration.

Keeping the respiratory system healthy

A healthy respiratory system can be maintained by:

• Not smoking — smoking damages the lungs and makes breathing difficult.
• Exercising regularly — exercise strengthens the lungs and improves breathing efficiency.
• Breathing clean air — avoiding polluted areas reduces damage to the lungs.

“Breathing and respiration are the same thing.” Breathing is the physical movement of air into and out of the lungs. Respiration is a chemical process that takes place in cells, where oxygen is used to break down food to release energy. Breathing supports respiration by supplying oxygen, but they are two different processes.

“We breathe in only oxygen and breathe out only carbon dioxide.” The air we breathe in contains about 21% oxygen, 78% nitrogen, and a small amount of carbon dioxide. The air we breathe out still contains oxygen (about 16%) and nitrogen, but has more carbon dioxide (about 4%) than inhaled air. We do not breathe in pure oxygen or breathe out pure carbon dioxide.

“The lungs push air in and out by themselves.” The lungs do not have muscles of their own and cannot move by themselves. Air moves in and out because of the movements of the diaphragm and the rib muscles. When these muscles move, they change the space inside the chest cavity, which causes the lungs to expand or compress.

“The diaphragm moves up when we breathe in.” This is a common mix-up. During inhalation, the diaphragm moves down (flattens) to create more space for the lungs to expand. During exhalation, the diaphragm moves up (returns to its dome shape) to reduce the space and push air out.