Respiratory System

 Important Respiratory Organs:

  • The human respiratory system consists of external nares or nistrils, nasal cavity, nasopharnyx, larynx, trachea, bronchi, bronchiole and lungs.
  • The air enters into the nasal cavity through the nostrils.
  • Larynx is a small box and it forms the connection between pharynx and the windpipe or trachea. Larynx is also known as voice box.
  • Larynx is covered by pieces of cartilage forming a box. In males, the adam's apple is the protuding cartilage of the voice box.
  • Trachea is a tubular structure of about 12 cm in length and 2.5 cm in diameter.
  • Lungs are paired structure present in the thoracic or pleural cavity.
  • During inhalation, diaphragm contracts and lungs increases while during exhalation, the diaphragm relaxes and the lungs are compressed.
  • The cycle of breathing (ventilation of lungs) consists of three phases:
    • Inspiration
    • Expiration and
    • Pause
anatomy of respiratory system
  • Inspiration is an active process. It is the result of muscle contraction.
  • Expiration is an passive process. It is the result of muscle relaxation.
  • The main muscles of respiration in normal breathing are intercostal muscles and diaphragm.
  • Larynx does not contribute to the breathing movements.
  • Breathing occurs involuntarily but its rate is controlled by the respiratory centre of brain. Under normal conditions rate of breathing is 15-18 times per minute.

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