Components of the Respiratory System

The respiratory system consists of the lungs, a group of passages connecting them to the outside environment and structures in the chest or thorax involved with moving air in and out of the lungs. The organs outside the thorax comprise the upper respiratory tract and those within the thorax the lower respiratory tract.

The components of the respiratory system are responsible for the following key functions:

  • Filter, warm and humidify incoming air.
  • Transport air from outside the body to the lungs.
  • Exchange of gases between the lungs and blood.

Air enters the respiratory system through the mouth and the nose. The air then passes through the larynx (where speech sounds are produced) and the trachea which is a tube that enters the thorax. In the thorax, the trachea splits into two smaller tubes called the bronchi. Each bronchus then divides again forming the bronchial tubes. The bronchial tubes lead directly into the lungs where they divide into many smaller tubes which connect to tiny sacs called alveoli.

Muscles in the chest wall, the intercostal muscles found between the ribs and the diaphragm, a sheet of muscle which separates the thorax and the abdomen, are responsible for drawing air into the lungs and expelling it.

Make yourself familiar with this diagram before attempting the labelling activity.

Two pleural membranes surround each lung, the outer pleural membrane lines the chest cavity. The inner pleural membrane covers the outside of each lung. Between the two membranes a pleural cavity is found and this is filled with fluid to prevent friction during breathing movements.


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