Respiratory System

The respiratory system consists of specific organs and structures used for the process of respiration in an organism. It is involved in the intake and exchange of oxygen and carbon dioxide between an organism and the environment.


The respiratory system includes:

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Bronchioles and smaller air passages
  • Lungs with pleura (coverings)
  • Intercostal muscles and diaphragm

All the cells of the body need energy. This energy is obtained from chemical reactions taking place in the presence of oxygen. Carbon dioxide is released as a product of these reactions. The respiratory system provides the means for supplying oxygen from the atmosphere to the cells of the body and also for the excretion of carbon dioxide back into the atmosphere.

Atmospheric air may be moist or dry, cold or warm and may also carry pollutants such as dust. As the air moves through the air passages, it is warmed or cooled to body temperature. Dust particles present in the air stick to the mucus present in the respiratory tract. This air is now available for gaseous exchange.

Blood acts as the carrier of oxygen and carbon dioxide between the lungs and cells of the body. Exchange of gases between blood and the lungs is called external respiration. Exchange of gases between the blood and cells of the body is called internal respiration.

Topics in this section

  • Nose and nasal cavity
    • Position and structure
    • Respiratory function of the nose
    • Olfactory function of the nose
  • Pharynx
    • Position
    • Structure
    • Functions
  • Larynx
    • Position
    • Structure
    • Functions
  • Trachea
    • Position
    • Structure
    • Functions
  • Bronchi and smaller air passages
    • Bronchi and bronchioles
      • Structure
      • Functions of air passages not involved in gaseous exchange
    • Respiratory bronchioles and alveoli
      • Structure
      • Functions of respiratory bronchioles and alveoli
  • Lungs
    • Position and associated structures
    • Organization of the lungs
    • Pleura and pleural cavity
    • Interior of the lungs
  • Respiration
    • Muscles of respiration
    • Cycle of respiration
    • Physiological variables affecting respiration
    • Lung volumes and capacities
    • Composition of air
    • Diffusion of gases
    • External respiration
    • Internal respiration
    • Transport of gases in the blood stream
    • Control of respiration
  • Disorders of the upper respiratory tract
    • Infectious and inflammatory disorders
    • Tumors
  • Diseases of the bronchi
    • Acute bronchitis
    • Chronic bronchitis
    • Asthma
    • Bronchiectasis
  • Disorders of the lungs
    • Emphysema
    • Pneumonia
    • Lung abscess
    • Tuberculosis
    • Pneumoconioses (occupational lung diseases)
    • Chemically induced lung diseases
    • Bronchial carcinoma
    • Lung collapse