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The Respiratory System The main function of the respiratory system is gas exchange (bring in oxygen and get out carbon dioxide). The main structures of the respiratory system are often divided into two main groups: 1. The Upper Respiratory Tract NASAL AND ORAL CAVITY – air enters and is warmed and moistened; mucus and hairs catch dust, bacteria, and particles PHARYNX – space at back of throat EPIGLOTTIS – flap of tissue in pharynx that covers opening to larynx to keep food and liquids out (see picture below) LARYNX – contains vocal cords TRACHEA – the windpipe; has semi-circular rings of cartilage to keep it from collapsing and has mucus and cilia to trap pollutants and sweep them up to the mouth to be swallowed or coughed out 2. The Lower Respiratory Tract BRONCHI – two tubes that form when trachea splits BRONCHIOLES – smaller tubes formed when the bronchi split – carry air deep into lung tissue ALVEOLI – small sacs at the end of each bronchus with a wall just one cell thick and surrounded by capillaries – where gas exchange occurs The Mechanics of Breathing Air is drawn into the lungs by changes in pressure. Inhalation When inhaling, the intercostal (between ribcage) muscles contract, causing the ribcage to move up and out. At the same time, the diaphragm is contracting, causing it to move down. These two actions cause the chest cavity to expand, creating an area of low pressure. Air moves from an area of high pressure to an area of low pressure and so air moves into the lungs. Exhalation When exhaling, the intercostal muscles (between ribs) relax, causing the ribcage to move down and in. At the same time, the diaphragm is relaxing, causing it to move up. These two actions cause the chest cavity to shrink, creating an area of high pressure. Air moves from an area of high pressure to an area of low pressure and so air moves out of the lungs.

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The Respiratory System

The main function of the respiratory system is gas exchange (bring in oxygen and get out carbon dioxide). The main structures of the respiratory system are often divided into two main groups:

1. The Upper Respiratory Tract

NASAL AND ORAL CAVITY – air enters and is warmed and moistened; mucus and hairs catch dust, bacteria, and particles

PHARYNX – space at back of throat

EPIGLOTTIS – flap of tissue in pharynx that covers opening to larynx to keep food and liquids out (see picture below)

LARYNX – contains vocal cords

TRACHEA – the windpipe; has semi-circular rings of cartilage to keep it from collapsing and has mucus and cilia to trap pollutants and sweep them up to the mouth to be swallowed or coughed out

2. The Lower Respiratory Tract

BRONCHI – two tubes that form when trachea splits

BRONCHIOLES – smaller tubes formed when the bronchi split – carry air deep into lung tissue

ALVEOLI – small sacs at the end of each bronchus with a wall just one cell thick and surrounded by capillaries – where gas exchange occurs

The Mechanics of Breathing

Air is drawn into the lungs by changes in pressure.

InhalationWhen inhaling, the intercostal (between ribcage) muscles contract, causing the ribcage to move up and out. At the same time, the diaphragm is contracting, causing it to move down. These two actions cause the chest cavity to expand, creating an area of low pressure. Air moves from an area of high pressure to an area of low pressure and so air moves into the lungs.

ExhalationWhen exhaling, the intercostal muscles (between ribs) relax, causing the ribcage to move down and in. At the same time, the diaphragm is relaxing, causing it to move up. These two actions cause the chest cavity to shrink, creating an area of high pressure. Air moves from an area of high pressure to an area of low pressure and so air moves out of the lungs.