1 2 Structure of the Respiratory System The

1. 2 Structure of the Respiratory System The trachea has a number of adaptations: · cartilage rings in the walls of the trachea help to keep it open · ciliated epithelium and goblet cells to clean the air before it reaches the lungs Goblet cells produce mucus which traps dust, dirt and bacteria to prevent them entering the lungs. Cilia are small hairs which beat to push the mucus back up the trachea so it can be swallowed and destroyed in the stomach. Clean air then enters the two bronchi, one bronchus going to each lung. The bronchi in the lungs split into smaller and smaller tubes called bronchioles. These end in microscopic air sacs called alveoli.

The following sentences describe the passage of air into the bloodstream. However they are in the wrong order. Rearrange the sentences into the correct order. Air is taken to each lung by a bronchus. This divided many times into smaller bronchioles. There are millions of these in each lung. They take air to the alveoli. Air enters the breathing system through the nose and mouth. Air goes the other way when we breathe out. Oxygen diffuses from the alveolus into the blood. It goes through the voice box and then down the trachea. Carbon dioxide diffuses from the blood in to the alveolus.

Inspiration Expiration The ribs move. . . The diaphragm. . . The volume of the thorax. . and pressure. . . . The volume of the thorax. . . and pressure. . . . . The lungs. . . . The pressure in the lungs is. . . . than outside, so air is sucked. . . . through the trachea so air moves. . . . through the trachea Explain the mechanics of inspiration and expiration. Remember to include the changes to volume and pressure. [6 marks] Answer

Explain how gas exchange takes place between the alveolus and the capillary. Include in your answer a description of how the alveolus is adapted to help this gas exchange. [6 marks] Answer: