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Question: How we breathe
New Page entitled Objectives

A Breath of Fresh Air In this Guided Learning Unit you are learning to: Describe the structure of the lungs Explain how the lungs clean themselves


New Page entitled The Lungs

The lungs are important to the body in the process of breathing . Breathing is when oxygen is taken in from the air outside and then on into the blood. In humans there are two lungs in the chest . The lungs are protected by the ribs . These are bones attached to the backbone to form a cage structure around the lungs. The lungs are the site of gas exchange with the air outside.


New Page entitled Inhaling

A breath starts when the ribs and the chest wall expand and the diaphragm tightens and flattens, which causes the lungs to fill with air. As the air enters our mouth and nose, the mucus membranes lining the mouth and nose make the air moist and warm, and they trap any particles. The air then passes down the throat into the trachea (or windpipe) , the bronchi , the bronchioles and then the alveoli .


New Page entitled Control System

Breathing is usually automatic and controlled by the respiratory centre at the base of the brain. We breathe during sleep and usually even during unconsciousness. Small sensors in the brain and aorta and carotid arteries monitor the blood. If there is too little oxygen in the blood these sensors trigger faster or deeper breathing. (In quiet breathing, the average adult inhales and exhales about 15 times a minute.)


Question: What controls our breathing?
New Page entitled Exhaling

The relaxation of the chest and diaphragm pushes the air out of the alveoli, through the bronchioles and the bronchi, up through the windpipe and out through the nose or mouth . When we are at rest, the process of breathing out requires no effort from the respiratory muscles. During vigorous exercise, however, many muscles assist in exhalation. The abdominal muscles are the most important of these. Abdominal muscles contract, raise abdominal pressure and push a relaxed diaphragm against the lungs , causing air to be expelled


New Page entitled The Alveoli

Air passes into the lungs and then into the alveoli . Once in the alveoli, oxygen diffuses (passes) from the alveoli into the blood . Red blood cells in the blood carry the oxygen to all the cells in the body . All cells produces carbon dioxide as waste. This is carried back to the lungs in the blood. It is then breathed out.


Question: Which is the correct route taken by oxygen travelling to the cells?
New Page entitled Keeping Lungs Clean

The air we breathe has dust and smoke particles and microbes (which cause disease) in it. These substances enter the air passages. if they are not removed the lungs can become diseased. The tubes in the lungs are lined with two types of special cells: Cilia with hair like extensions Mucus producers The mucus traps the harmful substance and the cilia sweep it up and out of the lungs into the throat where it is swallowed.


New Page entitled Respiration or Breathing?

Breathing is the action of air being taken into and out of the body. Air is taken into and out of the body by the physical movement of the ribs and diaphragm. Respiration is the production of energy to be used by all cells. This takes place in the cells. it is a chemical process