Breathing and Exchange of Gases Class 11 Notes - Chapter 17

Except for obligate anaerobes, every other organism from amoeba to humans need oxygen to survive. And evolution has charted a number of systems which enable the exchange of gases in organisms.

Respiratory Organs

For instance, insects breathe through a network of tubes called tracheae, fishes breathe through their gills, earthworms breathe through their moist skin by employing diffusion. Humans and nearly all other vertebrates breathe through their lungs or gills.

Interestingly, there are even more unconventional methods by which certain organisms breathe. Take the Labyrinth fish for example, apart from the gills, this fish has an organ called the labyrinth. This enables it to breathe the air from above the surface of the water.

Human Respiratory System

The human respiratory system is a set of organs and structures that help facilitate the exchange of gases in humans. It comprises of the following:

  1. Nose and Mouth
  2. Pharynx
  3. Larynx
  4. Trachea
  5. Bronchi and the Bronchioles
  6. Lungs

The actual exchange of gases takes place in tiny, innumerable structures called the alveoli and the capillaries in the lungs. Here, de-oxygenated blood gets re-oxygenated and sent to heart, where it is pumped to all the other parts of the body. Typically, most illness and disease of the respiratory system occur when the alveoli or bronchial tubes are damaged or inflamed. For instance, asthma is a disease where the airways get inflamed and it induces breathing difficulties.

Important Questions on Breathing and Exchange of Gases

  1. State the major transport mechanisms for CO2.
  2. Describe the process of inspiration.
  3. How do insects breathe?
  4. Define tidal volume.
  5. State the major components of the human respiratory system.

Further Reading:-


Practise This Question

The amino acid tryptophan is the precursor for the synthesis of :