The Respiratory System

Understanding the Respiratory System

  • The respiratory system includes organs and tissues involved in the process of breathing.
  • Main components are: the airways (nose, pharynx, larynx, trachea, bronchi, bronchioles), lungs, and muscles that enable breathing, including the diaphragm.
  • Its primary function is to supply the blood with oxygen in order for the blood to deliver oxygen to all parts of the body.
  • It also removes carbon dioxide, a waste product that cells produce when they use oxygen.

Breathing and Gas Exchange

  • Breathing refers to the process of taking in oxygen from the air and expelling carbon dioxide.
  • Oxygen is inhaled into the lungs and diffuses across the thin walled alveoli into the bloodstream.
  • Simultaneously, carbon dioxide in the high concentration in the blood diffuses across the alveoli and is exhaled.


  • Respiration is a chemical process where energy from food molecules is released.
  • Two types: aerobic respiration (with oxygen) and anaerobic respiration (without oxygen).
  • Aerobic respiration: Glucose + Oxygen -> Carbon dioxide + Water + Energy
  • Anaerobic respiration in muscles during hard exercise: Glucose -> Lactic acid + Energy
  • Anaerobic respiration in yeast cells: Glucose -> Ethanol + Carbon dioxide + Energy

Respiratory System Diseases

  • Various diseases can affect the respiratory system, such as bronchitis, asthma, and lung cancer.
  • Bronchitis: inflammation of the lining of the bronchial tubes, which carry air to and from the lungs.
  • Asthma: Air passages of the lungs become inflamed and narrowed causing difficulty in breathing.
  • Lung cancer: A malignant tumour that forms in the tissues of the lungs, usually in the cells lining air passages.

The Mechanism of Breathing

  • Inhalation (breathing in): The diaphragm contracts, pulling downwards. Intercostal muscles contract, raising ribcage up and out, increasing chest volume. This causes air pressure in chest to decrease, making air flow into lungs.
  • Exhalation (breathing out): The diaphragm and intercostal muscles relax, decreasing chest volume. This leads to increased air pressure in chest and air is forced out of lungs.

Remember, in the context of biology, oxygen is essential for life as it is required for the production of energy in all living cells. Knowledge about the respiratory system, its mechanism, and potential diseases can help us understand how our bodies function and how to take care of them.